Add libsimplewebm and libwebm thirdparty libraries

16 files changed, 10124 insertions, 0 deletions

diff --git a/thirdparty/README.md b/thirdparty/README.md
index f073bef8ec..1de2949d44 100644
--- a/thirdparty/README.md
+++ b/thirdparty/README.md
@@ -95,6 +95,12 @@ Files extracted from upstream source:
 - `scripts/pnglibconf.h.prebuilt` as `pnglibconf.h`
 
 
+## libsimplewebm
+
+- Upstream: https://github.com/zaps166/libsimplewebm
+- License: MIT, BSD-3-Clause
+
+
 ## libvorbis
 
 - Upstream: https://www.xiph.org/vorbis
diff --git a/thirdparty/libsimplewebm/LICENSE b/thirdparty/libsimplewebm/LICENSE
new file mode 100644
index 0000000000..058633ac18
--- /dev/null
+++ b/thirdparty/libsimplewebm/LICENSE
@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2016 Błażej Szczygieł
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/thirdparty/libsimplewebm/OpusVorbisDecoder.cpp b/thirdparty/libsimplewebm/OpusVorbisDecoder.cpp
new file mode 100644
index 0000000000..d7869f599b
--- /dev/null
+++ b/thirdparty/libsimplewebm/OpusVorbisDecoder.cpp
@@ -0,0 +1,224 @@
+/*
+	MIT License
+
+	Copyright (c) 2016 Błażej Szczygieł
+
+	Permission is hereby granted, free of charge, to any person obtaining a copy
+	of this software and associated documentation files (the "Software"), to deal
+	in the Software without restriction, including without limitation the rights
+	to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+	copies of the Software, and to permit persons to whom the Software is
+	furnished to do so, subject to the following conditions:
+
+	The above copyright notice and this permission notice shall be included in all
+	copies or substantial portions of the Software.
+
+	THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+	IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+	FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+	AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+	LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+	OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+	SOFTWARE.
+*/
+
+#include "OpusVorbisDecoder.hpp"
+
+#include <vorbis/codec.h>
+#include <opus/opus.h>
+
+#include <string.h>
+
+struct VorbisDecoder
+{
+	vorbis_info info;
+	vorbis_dsp_state dspState;
+	vorbis_block block;
+	ogg_packet op;
+
+	bool hasDSPState, hasBlock;
+};
+
+/**/
+
+OpusVorbisDecoder::OpusVorbisDecoder(const WebMDemuxer &demuxer) :
+	m_vorbis(NULL), m_opus(NULL),
+	m_numSamples(0),
+	m_channels(demuxer.getChannels())
+{
+	switch (demuxer.getAudioCodec())
+	{
+		case WebMDemuxer::AUDIO_VORBIS:
+			if (openVorbis(demuxer))
+				return;
+			break;
+		case WebMDemuxer::AUDIO_OPUS:
+			if (openOpus(demuxer))
+				return;
+			break;
+		default:
+			return;
+	}
+	close();
+}
+OpusVorbisDecoder::~OpusVorbisDecoder()
+{
+	close();
+}
+
+bool OpusVorbisDecoder::isOpen() const
+{
+	return (m_vorbis || m_opus);
+}
+
+bool OpusVorbisDecoder::getPCMS16(WebMFrame &frame, short *buffer, int &numOutSamples)
+{
+	if (m_vorbis)
+	{
+		m_vorbis->op.packet = frame.buffer;
+		m_vorbis->op.bytes = frame.bufferSize;
+
+		if (vorbis_synthesis(&m_vorbis->block, &m_vorbis->op))
+			return false;
+		if (vorbis_synthesis_blockin(&m_vorbis->dspState, &m_vorbis->block))
+			return false;
+
+		const int maxSamples = getBufferSamples();
+		int samplesCount, count = 0;
+		float **pcm;
+		while ((samplesCount = vorbis_synthesis_pcmout(&m_vorbis->dspState, &pcm)))
+		{
+			const int toConvert = samplesCount <= maxSamples ? samplesCount : maxSamples;
+			for (int c = 0; c < m_channels; ++c)
+			{
+				float *samples = pcm[c];
+				for (int i = 0, j = c; i < toConvert; ++i, j += m_channels)
+				{
+					int sample = samples[i] * 32767.0f;
+					if (sample > 32767)
+						sample = 32767;
+					else if (sample < -32768)
+						sample = -32768;
+					buffer[count + j] = sample;
+				}
+			}
+			vorbis_synthesis_read(&m_vorbis->dspState, toConvert);
+			count += toConvert;
+		}
+
+		numOutSamples = count;
+		return true;
+	}
+	else if (m_opus)
+	{
+		const int samples = opus_decode(m_opus, frame.buffer, frame.bufferSize, buffer, m_numSamples, 0);
+		if (samples >= 0)
+		{
+			numOutSamples = samples;
+			return true;
+		}
+	}
+	return false;
+}
+
+bool OpusVorbisDecoder::openVorbis(const WebMDemuxer &demuxer)
+{
+	size_t extradataSize = 0;
+	const unsigned char *extradata = demuxer.getAudioExtradata(extradataSize);
+
+	if (extradataSize < 3 || !extradata || extradata[0] != 2)
+		return false;
+
+	size_t headerSize[3] = {0};
+	size_t offset = 1;
+
+	/* Calculate three headers sizes */
+	for (int i = 0; i < 2; ++i)
+	{
+		for (;;)
+		{
+			if (offset >= extradataSize)
+				return false;
+			headerSize[i] += extradata[offset];
+			if (extradata[offset++] < 0xFF)
+				break;
+		}
+	}
+	headerSize[2] = extradataSize - (headerSize[0] + headerSize[1] + offset);
+
+	if (headerSize[0] + headerSize[1] + headerSize[2] + offset != extradataSize)
+		return false;
+
+	ogg_packet op[3];
+	memset(op, 0, sizeof op);
+
+	op[0].packet = (unsigned char *)extradata + offset;
+	op[0].bytes = headerSize[0];
+	op[0].b_o_s = 1;
+
+	op[1].packet = (unsigned char *)extradata + offset + headerSize[0];
+	op[1].bytes = headerSize[1];
+
+	op[2].packet = (unsigned char *)extradata + offset + headerSize[0] + headerSize[1];
+	op[2].bytes = headerSize[2];
+
+	m_vorbis = new VorbisDecoder;
+	m_vorbis->hasDSPState = m_vorbis->hasBlock = false;
+	vorbis_info_init(&m_vorbis->info);
+
+	/* Upload three Vorbis headers into libvorbis */
+	vorbis_comment vc;
+	vorbis_comment_init(&vc);
+	for (int i = 0; i < 3; ++i)
+	{
+		if (vorbis_synthesis_headerin(&m_vorbis->info, &vc, &op[i]))
+		{
+			vorbis_comment_clear(&vc);
+			return false;
+		}
+	}
+	vorbis_comment_clear(&vc);
+
+	if (vorbis_synthesis_init(&m_vorbis->dspState, &m_vorbis->info))
+		return false;
+	m_vorbis->hasDSPState = true;
+
+	if (m_vorbis->info.channels != m_channels || m_vorbis->info.rate != demuxer.getSampleRate())
+		return false;
+
+	if (vorbis_block_init(&m_vorbis->dspState, &m_vorbis->block))
+		return false;
+	m_vorbis->hasBlock = true;
+
+	memset(&m_vorbis->op, 0, sizeof m_vorbis->op);
+
+	m_numSamples = 4096 / m_channels;
+
+	return true;
+}
+bool OpusVorbisDecoder::openOpus(const WebMDemuxer &demuxer)
+{
+	int opusErr = 0;
+	m_opus = opus_decoder_create(demuxer.getSampleRate(), m_channels, &opusErr);
+	if (!opusErr)
+	{
+		m_numSamples = demuxer.getSampleRate() * 0.06 + 0.5; //Maximum frame size (for 60 ms frame)
+		return true;
+	}
+	return false;
+}
+
+void OpusVorbisDecoder::close()
+{
+	if (m_vorbis)
+	{
+		if (m_vorbis->hasBlock)
+			vorbis_block_clear(&m_vorbis->block);
+		if (m_vorbis->hasDSPState)
+			vorbis_dsp_clear(&m_vorbis->dspState);
+		vorbis_info_clear(&m_vorbis->info);
+		delete m_vorbis;
+	}
+	if (m_opus)
+		opus_decoder_destroy(m_opus);
+}
diff --git a/thirdparty/libsimplewebm/OpusVorbisDecoder.hpp b/thirdparty/libsimplewebm/OpusVorbisDecoder.hpp
new file mode 100644
index 0000000000..bcdca731ee
--- /dev/null
+++ b/thirdparty/libsimplewebm/OpusVorbisDecoder.hpp
@@ -0,0 +1,63 @@
+/*
+	MIT License
+
+	Copyright (c) 2016 Błażej Szczygieł
+
+	Permission is hereby granted, free of charge, to any person obtaining a copy
+	of this software and associated documentation files (the "Software"), to deal
+	in the Software without restriction, including without limitation the rights
+	to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+	copies of the Software, and to permit persons to whom the Software is
+	furnished to do so, subject to the following conditions:
+
+	The above copyright notice and this permission notice shall be included in all
+	copies or substantial portions of the Software.
+
+	THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+	IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+	FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+	AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+	LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+	OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+	SOFTWARE.
+*/
+
+#ifndef OPUSVORBISDECODER_HPP
+#define OPUSVORBISDECODER_HPP
+
+#include "WebMDemuxer.hpp"
+
+struct VorbisDecoder;
+struct OpusDecoder;
+
+class OpusVorbisDecoder
+{
+	OpusVorbisDecoder(const OpusVorbisDecoder &);
+	void operator =(const OpusVorbisDecoder &);
+public:
+	OpusVorbisDecoder(const WebMDemuxer &demuxer);
+	~OpusVorbisDecoder();
+
+	bool isOpen() const;
+
+	inline int getBufferSamples() const
+	{
+		return m_numSamples;
+	}
+
+	bool getPCMS16(WebMFrame &frame, short *buffer, int &numOutSamples);
+
+private:
+	bool openVorbis(const WebMDemuxer &demuxer);
+	bool openOpus(const WebMDemuxer &demuxer);
+
+	void close();
+
+	VorbisDecoder *m_vorbis;
+	OpusDecoder *m_opus;
+	int m_numSamples;
+	int m_channels;
+
+};
+
+#endif // OPUSVORBISDECODER_HPP
diff --git a/thirdparty/libsimplewebm/VPXDecoder.cpp b/thirdparty/libsimplewebm/VPXDecoder.cpp
new file mode 100644
index 0000000000..3f77b8f5cd
--- /dev/null
+++ b/thirdparty/libsimplewebm/VPXDecoder.cpp
@@ -0,0 +1,142 @@
+/*
+	MIT License
+
+	Copyright (c) 2016 Błażej Szczygieł
+
+	Permission is hereby granted, free of charge, to any person obtaining a copy
+	of this software and associated documentation files (the "Software"), to deal
+	in the Software without restriction, including without limitation the rights
+	to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+	copies of the Software, and to permit persons to whom the Software is
+	furnished to do so, subject to the following conditions:
+
+	The above copyright notice and this permission notice shall be included in all
+	copies or substantial portions of the Software.
+
+	THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+	IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+	FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+	AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+	LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+	OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+	SOFTWARE.
+*/
+
+#include "VPXDecoder.hpp"
+
+#include <vpx/vpx_decoder.h>
+#include <vpx/vp8dx.h>
+
+#include <stdlib.h>
+#include <string.h>
+
+VPXDecoder::VPXDecoder(const WebMDemuxer &demuxer, unsigned threads) :
+	m_ctx(NULL),
+	m_iter(NULL),
+	m_delay(0)
+{
+	if (threads > 8)
+		threads = 8;
+	else if (threads < 1)
+		threads = 1;
+
+	const vpx_codec_dec_cfg_t codecCfg = {
+		threads,
+		0,
+		0
+	};
+	vpx_codec_iface_t *codecIface = NULL;
+
+	switch (demuxer.getVideoCodec())
+	{
+		case WebMDemuxer::VIDEO_VP8:
+			codecIface = vpx_codec_vp8_dx();
+			break;
+		case WebMDemuxer::VIDEO_VP9:
+			codecIface = vpx_codec_vp9_dx();
+			m_delay = threads - 1;
+			break;
+		default:
+			return;
+	}
+
+	m_ctx = new vpx_codec_ctx_t;
+	if (vpx_codec_dec_init(m_ctx, codecIface, &codecCfg, m_delay > 0 ? VPX_CODEC_USE_FRAME_THREADING : 0))
+	{
+		delete m_ctx;
+		m_ctx = NULL;
+	}
+}
+VPXDecoder::~VPXDecoder()
+{
+	if (m_ctx)
+	{
+		vpx_codec_destroy(m_ctx);
+		delete m_ctx;
+	}
+}
+
+bool VPXDecoder::decode(const WebMFrame &frame)
+{
+	m_iter = NULL;
+	return !vpx_codec_decode(m_ctx, frame.buffer, frame.bufferSize, NULL, 0);
+}
+VPXDecoder::IMAGE_ERROR VPXDecoder::getImage(Image &image)
+{
+	IMAGE_ERROR err = NO_FRAME;
+	if (vpx_image_t *img = vpx_codec_get_frame(m_ctx, &m_iter))
+	{
+		if ((img->fmt & VPX_IMG_FMT_PLANAR) && !(img->fmt & (VPX_IMG_FMT_HAS_ALPHA | VPX_IMG_FMT_HIGHBITDEPTH)))
+		{
+			if (img->stride[0] && img->stride[1] && img->stride[2])
+			{
+				const int uPlane = !!(img->fmt & VPX_IMG_FMT_UV_FLIP) + 1;
+				const int vPlane =  !(img->fmt & VPX_IMG_FMT_UV_FLIP) + 1;
+
+				image.w = img->d_w;
+				image.h = img->d_h;
+				image.chromaShiftW = img->x_chroma_shift;
+				image.chromaShiftH = img->y_chroma_shift;
+
+				image.planes[0] = img->planes[0];
+				image.planes[1] = img->planes[uPlane];
+				image.planes[2] = img->planes[vPlane];
+
+				image.linesize[0] = img->stride[0];
+				image.linesize[1] = img->stride[uPlane];
+				image.linesize[2] = img->stride[vPlane];
+
+				err = NO_ERROR;
+			}
+		}
+		else
+		{
+			err = UNSUPPORTED_FRAME;
+		}
+	}
+	return err;
+}
+
+/**/
+
+#if 0
+
+static inline int ceilRshift(int val, int shift)
+{
+	return (val + (1 << shift) - 1) >> shift;
+}
+
+int VPXDecoder::Image::getWidth(int plane) const
+{
+	if (!plane)
+		return w;
+	return ceilRshift(w, chromaShiftW);
+}
+int VPXDecoder::Image::getHeight(int plane) const
+{
+	if (!plane)
+		return h;
+	return ceilRshift(h, chromaShiftH);
+}
+
+#endif
diff --git a/thirdparty/libsimplewebm/VPXDecoder.hpp b/thirdparty/libsimplewebm/VPXDecoder.hpp
new file mode 100644
index 0000000000..6108395871
--- /dev/null
+++ b/thirdparty/libsimplewebm/VPXDecoder.hpp
@@ -0,0 +1,80 @@
+/*
+	MIT License
+
+	Copyright (c) 2016 Błażej Szczygieł
+
+	Permission is hereby granted, free of charge, to any person obtaining a copy
+	of this software and associated documentation files (the "Software"), to deal
+	in the Software without restriction, including without limitation the rights
+	to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+	copies of the Software, and to permit persons to whom the Software is
+	furnished to do so, subject to the following conditions:
+
+	The above copyright notice and this permission notice shall be included in all
+	copies or substantial portions of the Software.
+
+	THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+	IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+	FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+	AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+	LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+	OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+	SOFTWARE.
+*/
+
+#ifndef VPXDECODER_HPP
+#define VPXDECODER_HPP
+
+#include "WebMDemuxer.hpp"
+
+struct vpx_codec_ctx;
+
+class VPXDecoder
+{
+	VPXDecoder(const VPXDecoder &);
+	void operator =(const VPXDecoder &);
+public:
+	class Image
+	{
+	public:
+#if 0
+		int getWidth(int plane) const;
+		int getHeight(int plane) const;
+#endif
+
+		int w, h;
+		int chromaShiftW, chromaShiftH;
+		unsigned char *planes[3];
+		int linesize[3];
+	};
+
+	enum IMAGE_ERROR
+	{
+		UNSUPPORTED_FRAME = -1,
+		NO_ERROR,
+		NO_FRAME
+	};
+
+	VPXDecoder(const WebMDemuxer &demuxer, unsigned threads = 1);
+	~VPXDecoder();
+
+	inline bool isOpen() const
+	{
+		return (bool)m_ctx;
+	}
+
+	inline int getFramesDelay() const
+	{
+		return m_delay;
+	}
+
+	bool decode(const WebMFrame &frame);
+	IMAGE_ERROR getImage(Image &image); //The data is NOT copied! Only 3-plane, 8-bit images are supported.
+
+private:
+	vpx_codec_ctx *m_ctx;
+	const void *m_iter;
+	int m_delay;
+};
+
+#endif // VPXDECODER_HPP
diff --git a/thirdparty/libsimplewebm/WebMDemuxer.cpp b/thirdparty/libsimplewebm/WebMDemuxer.cpp
new file mode 100644
index 0000000000..cb63deccd5
--- /dev/null
+++ b/thirdparty/libsimplewebm/WebMDemuxer.cpp
@@ -0,0 +1,241 @@
+/*
+	MIT License
+
+	Copyright (c) 2016 Błażej Szczygieł
+
+	Permission is hereby granted, free of charge, to any person obtaining a copy
+	of this software and associated documentation files (the "Software"), to deal
+	in the Software without restriction, including without limitation the rights
+	to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+	copies of the Software, and to permit persons to whom the Software is
+	furnished to do so, subject to the following conditions:
+
+	The above copyright notice and this permission notice shall be included in all
+	copies or substantial portions of the Software.
+
+	THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+	IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+	FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+	AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+	LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+	OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+	SOFTWARE.
+*/
+
+#include "WebMDemuxer.hpp"
+
+#include "mkvparser/mkvparser.h"
+
+#include <assert.h>
+#include <stdlib.h>
+#include <string.h>
+
+WebMFrame::WebMFrame() :
+	bufferSize(0), bufferCapacity(0),
+	buffer(NULL),
+	time(0),
+	key(false)
+{}
+WebMFrame::~WebMFrame()
+{
+	free(buffer);
+}
+
+/**/
+
+WebMDemuxer::WebMDemuxer(mkvparser::IMkvReader *reader, int videoTrack, int audioTrack) :
+	m_reader(reader),
+	m_segment(NULL),
+	m_cluster(NULL), m_block(NULL), m_blockEntry(NULL),
+	m_blockFrameIndex(0),
+	m_videoTrack(NULL), m_vCodec(NO_VIDEO),
+	m_audioTrack(NULL), m_aCodec(NO_AUDIO),
+	m_isOpen(false),
+	m_eos(false)
+{
+	long long pos = 0;
+	if (mkvparser::EBMLHeader().Parse(m_reader, pos))
+		return;
+
+	if (mkvparser::Segment::CreateInstance(m_reader, pos, m_segment))
+		return;
+
+	if (m_segment->Load() < 0)
+		return;
+
+	const mkvparser::Tracks *tracks = m_segment->GetTracks();
+	const unsigned long tracksCount = tracks->GetTracksCount();
+	int currVideoTrack = -1, currAudioTrack = -1;
+	for (unsigned long i = 0; i < tracksCount; ++i)
+	{
+		const mkvparser::Track *track = tracks->GetTrackByIndex(i);
+		if (const char *codecId = track->GetCodecId())
+		{
+			if ((!m_videoTrack || currVideoTrack != videoTrack) && track->GetType() == mkvparser::Track::kVideo)
+			{
+				if (!strcmp(codecId, "V_VP8"))
+					m_vCodec = VIDEO_VP8;
+				else if (!strcmp(codecId, "V_VP9"))
+					m_vCodec = VIDEO_VP9;
+				if (m_vCodec != NO_VIDEO)
+					m_videoTrack = static_cast<const mkvparser::VideoTrack *>(track);
+				++currVideoTrack;
+			}
+			if ((!m_audioTrack || currAudioTrack != audioTrack) && track->GetType() == mkvparser::Track::kAudio)
+			{
+				if (!strcmp(codecId, "A_VORBIS"))
+					m_aCodec = AUDIO_VORBIS;
+				else if (!strcmp(codecId, "A_OPUS"))
+					m_aCodec = AUDIO_OPUS;
+				if (m_aCodec != NO_AUDIO)
+					m_audioTrack = static_cast<const mkvparser::AudioTrack *>(track);
+				++currAudioTrack;
+			}
+		}
+	}
+	if (!m_videoTrack && !m_audioTrack)
+		return;
+
+	m_isOpen = true;
+}
+WebMDemuxer::~WebMDemuxer()
+{
+	delete m_segment;
+	delete m_reader;
+}
+
+double WebMDemuxer::getLength() const
+{
+	return m_segment->GetDuration() / 1e9;
+}
+
+WebMDemuxer::VIDEO_CODEC WebMDemuxer::getVideoCodec() const
+{
+	return m_vCodec;
+}
+int WebMDemuxer::getWidth() const
+{
+	return m_videoTrack->GetWidth();
+}
+int WebMDemuxer::getHeight() const
+{
+	return m_videoTrack->GetHeight();
+}
+
+WebMDemuxer::AUDIO_CODEC WebMDemuxer::getAudioCodec() const
+{
+	return m_aCodec;
+}
+const unsigned char *WebMDemuxer::getAudioExtradata(size_t &size) const
+{
+	return m_audioTrack->GetCodecPrivate(size);
+}
+double WebMDemuxer::getSampleRate() const
+{
+	return m_audioTrack->GetSamplingRate();
+}
+int WebMDemuxer::getChannels() const
+{
+	return m_audioTrack->GetChannels();
+}
+int WebMDemuxer::getAudioDepth() const
+{
+	return m_audioTrack->GetBitDepth();
+}
+
+bool WebMDemuxer::readFrame(WebMFrame *videoFrame, WebMFrame *audioFrame)
+{
+	const long videoTrackNumber = (videoFrame && m_videoTrack) ? m_videoTrack->GetNumber() : 0;
+	const long audioTrackNumber = (audioFrame && m_audioTrack) ? m_audioTrack->GetNumber() : 0;
+	bool blockEntryEOS = false;
+
+	if (videoFrame)
+		videoFrame->bufferSize = 0;
+	if (audioFrame)
+		audioFrame->bufferSize = 0;
+
+	if (videoTrackNumber == 0 && audioTrackNumber == 0)
+		return false;
+
+	if (m_eos)
+		return false;
+
+	if (!m_cluster)
+		m_cluster = m_segment->GetFirst();
+
+	do
+	{
+		bool getNewBlock = false;
+		long status = 0;
+		if (!m_blockEntry && !blockEntryEOS)
+		{
+			status = m_cluster->GetFirst(m_blockEntry);
+			getNewBlock = true;
+		}
+		else if (blockEntryEOS || m_blockEntry->EOS())
+		{
+			m_cluster = m_segment->GetNext(m_cluster);
+			if (!m_cluster || m_cluster->EOS())
+			{
+				m_eos = true;
+				return false;
+			}
+			status = m_cluster->GetFirst(m_blockEntry);
+			blockEntryEOS = false;
+			getNewBlock = true;
+		}
+		else if (!m_block || m_blockFrameIndex == m_block->GetFrameCount() || notSupportedTrackNumber(videoTrackNumber, audioTrackNumber))
+		{
+			status = m_cluster->GetNext(m_blockEntry, m_blockEntry);
+			if (!m_blockEntry  || m_blockEntry->EOS())
+			{
+				blockEntryEOS = true;
+				continue;
+			}
+			getNewBlock = true;
+		}
+		if (status || !m_blockEntry)
+			return false;
+		if (getNewBlock)
+		{
+			m_block = m_blockEntry->GetBlock();
+			m_blockFrameIndex = 0;
+		}
+	} while (blockEntryEOS || notSupportedTrackNumber(videoTrackNumber, audioTrackNumber));
+
+	WebMFrame *frame = NULL;
+
+	const long trackNumber = m_block->GetTrackNumber();
+	if (trackNumber == videoTrackNumber)
+		frame = videoFrame;
+	else if (trackNumber == audioTrackNumber)
+		frame = audioFrame;
+	else
+	{
+		//Should not be possible
+		assert(trackNumber == videoTrackNumber || trackNumber == audioTrackNumber);
+		return false;
+	}
+
+	const mkvparser::Block::Frame &blockFrame = m_block->GetFrame(m_blockFrameIndex++);
+	if (blockFrame.len > frame->bufferCapacity)
+	{
+		unsigned char *newBuff = (unsigned char *)realloc(frame->buffer, frame->bufferCapacity = blockFrame.len);
+		if (newBuff)
+			frame->buffer = newBuff;
+		else // Out of memory
+			return false;
+	}
+	frame->bufferSize = blockFrame.len;
+
+	frame->time = m_block->GetTime(m_cluster) / 1e9;
+	frame->key  = m_block->IsKey();
+
+	return !blockFrame.Read(m_reader, frame->buffer);
+}
+
+inline bool WebMDemuxer::notSupportedTrackNumber(long videoTrackNumber, long audioTrackNumber) const
+{
+	const long trackNumber = m_block->GetTrackNumber();
+	return (trackNumber != videoTrackNumber && trackNumber != audioTrackNumber);
+}
diff --git a/thirdparty/libsimplewebm/WebMDemuxer.hpp b/thirdparty/libsimplewebm/WebMDemuxer.hpp
new file mode 100644
index 0000000000..a45ddb3f26
--- /dev/null
+++ b/thirdparty/libsimplewebm/WebMDemuxer.hpp
@@ -0,0 +1,125 @@
+/*
+	MIT License
+
+	Copyright (c) 2016 Błażej Szczygieł
+
+	Permission is hereby granted, free of charge, to any person obtaining a copy
+	of this software and associated documentation files (the "Software"), to deal
+	in the Software without restriction, including without limitation the rights
+	to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+	copies of the Software, and to permit persons to whom the Software is
+	furnished to do so, subject to the following conditions:
+
+	The above copyright notice and this permission notice shall be included in all
+	copies or substantial portions of the Software.
+
+	THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+	IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+	FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+	AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+	LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+	OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+	SOFTWARE.
+*/
+
+#ifndef WEBMDEMUXER_HPP
+#define WEBMDEMUXER_HPP
+
+#include <stddef.h>
+
+namespace mkvparser {
+	class IMkvReader;
+	class Segment;
+	class Cluster;
+	class Block;
+	class BlockEntry;
+	class VideoTrack;
+	class AudioTrack;
+}
+
+class WebMFrame
+{
+	WebMFrame(const WebMFrame &);
+	void operator =(const WebMFrame &);
+public:
+	WebMFrame();
+	~WebMFrame();
+
+	inline bool isValid() const
+	{
+		return bufferSize > 0;
+	}
+
+	long bufferSize, bufferCapacity;
+	unsigned char *buffer;
+	double time;
+	bool key;
+};
+
+class WebMDemuxer
+{
+	WebMDemuxer(const WebMDemuxer &);
+	void operator =(const WebMDemuxer &);
+public:
+	enum VIDEO_CODEC
+	{
+		NO_VIDEO,
+		VIDEO_VP8,
+		VIDEO_VP9
+	};
+	enum AUDIO_CODEC
+	{
+		NO_AUDIO,
+		AUDIO_VORBIS,
+		AUDIO_OPUS
+	};
+
+	WebMDemuxer(mkvparser::IMkvReader *reader, int videoTrack = 0, int audioTrack = 0);
+	~WebMDemuxer();
+
+	inline bool isOpen() const
+	{
+		return m_isOpen;
+	}
+	inline bool isEOS() const
+	{
+		return m_eos;
+	}
+
+	double getLength() const;
+
+	VIDEO_CODEC getVideoCodec() const;
+	int getWidth() const;
+	int getHeight() const;
+
+	AUDIO_CODEC getAudioCodec() const;
+	const unsigned char *getAudioExtradata(size_t &size) const; // Needed for Vorbis
+	double getSampleRate() const;
+	int getChannels() const;
+	int getAudioDepth() const;
+
+	bool readFrame(WebMFrame *videoFrame, WebMFrame *audioFrame);
+
+private:
+	inline bool notSupportedTrackNumber(long videoTrackNumber, long audioTrackNumber) const;
+
+	mkvparser::IMkvReader *m_reader;
+	mkvparser::Segment *m_segment;
+
+	const mkvparser::Cluster *m_cluster;
+	const mkvparser::Block *m_block;
+	const mkvparser::BlockEntry *m_blockEntry;
+
+	int m_blockFrameIndex;
+
+	const mkvparser::VideoTrack *m_videoTrack;
+	VIDEO_CODEC m_vCodec;
+
+	const mkvparser::AudioTrack *m_audioTrack;
+	AUDIO_CODEC m_aCodec;
+
+	bool m_isOpen;
+	bool m_eos;
+};
+
+#endif // WEBMDEMUXER_HPP
diff --git a/thirdparty/libsimplewebm/libwebm/AUTHORS.TXT b/thirdparty/libsimplewebm/libwebm/AUTHORS.TXT
new file mode 100644
index 0000000000..9686ac13eb
--- /dev/null
+++ b/thirdparty/libsimplewebm/libwebm/AUTHORS.TXT
@@ -0,0 +1,4 @@
+# Names should be added to this file like so:
+# Name or Organization <email address>
+
+Google Inc.
diff --git a/thirdparty/libsimplewebm/libwebm/LICENSE.TXT b/thirdparty/libsimplewebm/libwebm/LICENSE.TXT
new file mode 100644
index 0000000000..7a6f99547d
--- /dev/null
+++ b/thirdparty/libsimplewebm/libwebm/LICENSE.TXT
@@ -0,0 +1,30 @@
+Copyright (c) 2010, Google Inc. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+  * Redistributions of source code must retain the above copyright
+    notice, this list of conditions and the following disclaimer.
+
+  * Redistributions in binary form must reproduce the above copyright
+    notice, this list of conditions and the following disclaimer in
+    the documentation and/or other materials provided with the
+    distribution.
+
+  * Neither the name of Google nor the names of its contributors may
+    be used to endorse or promote products derived from this software
+    without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
diff --git a/thirdparty/libsimplewebm/libwebm/PATENTS.TXT b/thirdparty/libsimplewebm/libwebm/PATENTS.TXT
new file mode 100644
index 0000000000..caedf607e9
--- /dev/null
+++ b/thirdparty/libsimplewebm/libwebm/PATENTS.TXT
@@ -0,0 +1,23 @@
+Additional IP Rights Grant (Patents)
+------------------------------------
+
+"These implementations" means the copyrightable works that implement the WebM
+codecs distributed by Google as part of the WebM Project.
+
+Google hereby grants to you a perpetual, worldwide, non-exclusive, no-charge,
+royalty-free, irrevocable (except as stated in this section) patent license to
+make, have made, use, offer to sell, sell, import, transfer, and otherwise
+run, modify and propagate the contents of these implementations of WebM, where
+such license applies only to those patent claims, both currently owned by
+Google and acquired in the future, licensable by Google that are necessarily
+infringed by these implementations of WebM. This grant does not include claims
+that would be infringed only as a consequence of further modification of these
+implementations. If you or your agent or exclusive licensee institute or order
+or agree to the institution of patent litigation or any other patent
+enforcement activity against any entity (including a cross-claim or
+counterclaim in a lawsuit) alleging that any of these implementations of WebM
+or any code incorporated within any of these implementations of WebM
+constitute direct or contributory patent infringement, or inducement of
+patent infringement, then any patent rights granted to you under this License
+for these implementations of WebM shall terminate as of the date such
+litigation is filed.
diff --git a/thirdparty/libsimplewebm/libwebm/README.libvpx b/thirdparty/libsimplewebm/libwebm/README.libvpx
new file mode 100644
index 0000000000..ae62f36525
--- /dev/null
+++ b/thirdparty/libsimplewebm/libwebm/README.libvpx
@@ -0,0 +1,11 @@
+URL: https://chromium.googlesource.com/webm/libwebm
+Version: 32d5ac49414a8914ec1e1f285f3f927c6e8ec29d
+License: BSD
+License File: LICENSE.txt
+
+Description:
+libwebm is used to handle WebM container I/O.
+
+Local Changes:
+* Removed: "mkvmuxer", "hdr_util", "file_util", "mkv_reader".
+* Make "~IMkvRerader()" public.
diff --git a/thirdparty/libsimplewebm/libwebm/common/webmids.h b/thirdparty/libsimplewebm/libwebm/common/webmids.h
new file mode 100644
index 0000000000..32a0c5fb91
--- /dev/null
+++ b/thirdparty/libsimplewebm/libwebm/common/webmids.h
@@ -0,0 +1,184 @@
+// Copyright (c) 2012 The WebM project authors. All Rights Reserved.
+//
+// Use of this source code is governed by a BSD-style license
+// that can be found in the LICENSE file in the root of the source
+// tree. An additional intellectual property rights grant can be found
+// in the file PATENTS.  All contributing project authors may
+// be found in the AUTHORS file in the root of the source tree.
+
+#ifndef COMMON_WEBMIDS_H_
+#define COMMON_WEBMIDS_H_
+
+namespace libwebm {
+
+enum MkvId {
+  kMkvEBML = 0x1A45DFA3,
+  kMkvEBMLVersion = 0x4286,
+  kMkvEBMLReadVersion = 0x42F7,
+  kMkvEBMLMaxIDLength = 0x42F2,
+  kMkvEBMLMaxSizeLength = 0x42F3,
+  kMkvDocType = 0x4282,
+  kMkvDocTypeVersion = 0x4287,
+  kMkvDocTypeReadVersion = 0x4285,
+  kMkvVoid = 0xEC,
+  kMkvSignatureSlot = 0x1B538667,
+  kMkvSignatureAlgo = 0x7E8A,
+  kMkvSignatureHash = 0x7E9A,
+  kMkvSignaturePublicKey = 0x7EA5,
+  kMkvSignature = 0x7EB5,
+  kMkvSignatureElements = 0x7E5B,
+  kMkvSignatureElementList = 0x7E7B,
+  kMkvSignedElement = 0x6532,
+  // segment
+  kMkvSegment = 0x18538067,
+  // Meta Seek Information
+  kMkvSeekHead = 0x114D9B74,
+  kMkvSeek = 0x4DBB,
+  kMkvSeekID = 0x53AB,
+  kMkvSeekPosition = 0x53AC,
+  // Segment Information
+  kMkvInfo = 0x1549A966,
+  kMkvTimecodeScale = 0x2AD7B1,
+  kMkvDuration = 0x4489,
+  kMkvDateUTC = 0x4461,
+  kMkvTitle = 0x7BA9,
+  kMkvMuxingApp = 0x4D80,
+  kMkvWritingApp = 0x5741,
+  // Cluster
+  kMkvCluster = 0x1F43B675,
+  kMkvTimecode = 0xE7,
+  kMkvPrevSize = 0xAB,
+  kMkvBlockGroup = 0xA0,
+  kMkvBlock = 0xA1,
+  kMkvBlockDuration = 0x9B,
+  kMkvReferenceBlock = 0xFB,
+  kMkvLaceNumber = 0xCC,
+  kMkvSimpleBlock = 0xA3,
+  kMkvBlockAdditions = 0x75A1,
+  kMkvBlockMore = 0xA6,
+  kMkvBlockAddID = 0xEE,
+  kMkvBlockAdditional = 0xA5,
+  kMkvDiscardPadding = 0x75A2,
+  // Track
+  kMkvTracks = 0x1654AE6B,
+  kMkvTrackEntry = 0xAE,
+  kMkvTrackNumber = 0xD7,
+  kMkvTrackUID = 0x73C5,
+  kMkvTrackType = 0x83,
+  kMkvFlagEnabled = 0xB9,
+  kMkvFlagDefault = 0x88,
+  kMkvFlagForced = 0x55AA,
+  kMkvFlagLacing = 0x9C,
+  kMkvDefaultDuration = 0x23E383,
+  kMkvMaxBlockAdditionID = 0x55EE,
+  kMkvName = 0x536E,
+  kMkvLanguage = 0x22B59C,
+  kMkvCodecID = 0x86,
+  kMkvCodecPrivate = 0x63A2,
+  kMkvCodecName = 0x258688,
+  kMkvCodecDelay = 0x56AA,
+  kMkvSeekPreRoll = 0x56BB,
+  // video
+  kMkvVideo = 0xE0,
+  kMkvFlagInterlaced = 0x9A,
+  kMkvStereoMode = 0x53B8,
+  kMkvAlphaMode = 0x53C0,
+  kMkvPixelWidth = 0xB0,
+  kMkvPixelHeight = 0xBA,
+  kMkvPixelCropBottom = 0x54AA,
+  kMkvPixelCropTop = 0x54BB,
+  kMkvPixelCropLeft = 0x54CC,
+  kMkvPixelCropRight = 0x54DD,
+  kMkvDisplayWidth = 0x54B0,
+  kMkvDisplayHeight = 0x54BA,
+  kMkvDisplayUnit = 0x54B2,
+  kMkvAspectRatioType = 0x54B3,
+  kMkvFrameRate = 0x2383E3,
+  // end video
+  // colour
+  kMkvColour = 0x55B0,
+  kMkvMatrixCoefficients = 0x55B1,
+  kMkvBitsPerChannel = 0x55B2,
+  kMkvChromaSubsamplingHorz = 0x55B3,
+  kMkvChromaSubsamplingVert = 0x55B4,
+  kMkvCbSubsamplingHorz = 0x55B5,
+  kMkvCbSubsamplingVert = 0x55B6,
+  kMkvChromaSitingHorz = 0x55B7,
+  kMkvChromaSitingVert = 0x55B8,
+  kMkvRange = 0x55B9,
+  kMkvTransferCharacteristics = 0x55BA,
+  kMkvPrimaries = 0x55BB,
+  kMkvMaxCLL = 0x55BC,
+  kMkvMaxFALL = 0x55BD,
+  // mastering metadata
+  kMkvMasteringMetadata = 0x55D0,
+  kMkvPrimaryRChromaticityX = 0x55D1,
+  kMkvPrimaryRChromaticityY = 0x55D2,
+  kMkvPrimaryGChromaticityX = 0x55D3,
+  kMkvPrimaryGChromaticityY = 0x55D4,
+  kMkvPrimaryBChromaticityX = 0x55D5,
+  kMkvPrimaryBChromaticityY = 0x55D6,
+  kMkvWhitePointChromaticityX = 0x55D7,
+  kMkvWhitePointChromaticityY = 0x55D8,
+  kMkvLuminanceMax = 0x55D9,
+  kMkvLuminanceMin = 0x55DA,
+  // end mastering metadata
+  // end colour
+  // audio
+  kMkvAudio = 0xE1,
+  kMkvSamplingFrequency = 0xB5,
+  kMkvOutputSamplingFrequency = 0x78B5,
+  kMkvChannels = 0x9F,
+  kMkvBitDepth = 0x6264,
+  // end audio
+  // ContentEncodings
+  kMkvContentEncodings = 0x6D80,
+  kMkvContentEncoding = 0x6240,
+  kMkvContentEncodingOrder = 0x5031,
+  kMkvContentEncodingScope = 0x5032,
+  kMkvContentEncodingType = 0x5033,
+  kMkvContentCompression = 0x5034,
+  kMkvContentCompAlgo = 0x4254,
+  kMkvContentCompSettings = 0x4255,
+  kMkvContentEncryption = 0x5035,
+  kMkvContentEncAlgo = 0x47E1,
+  kMkvContentEncKeyID = 0x47E2,
+  kMkvContentSignature = 0x47E3,
+  kMkvContentSigKeyID = 0x47E4,
+  kMkvContentSigAlgo = 0x47E5,
+  kMkvContentSigHashAlgo = 0x47E6,
+  kMkvContentEncAESSettings = 0x47E7,
+  kMkvAESSettingsCipherMode = 0x47E8,
+  kMkvAESSettingsCipherInitData = 0x47E9,
+  // end ContentEncodings
+  // Cueing Data
+  kMkvCues = 0x1C53BB6B,
+  kMkvCuePoint = 0xBB,
+  kMkvCueTime = 0xB3,
+  kMkvCueTrackPositions = 0xB7,
+  kMkvCueTrack = 0xF7,
+  kMkvCueClusterPosition = 0xF1,
+  kMkvCueBlockNumber = 0x5378,
+  // Chapters
+  kMkvChapters = 0x1043A770,
+  kMkvEditionEntry = 0x45B9,
+  kMkvChapterAtom = 0xB6,
+  kMkvChapterUID = 0x73C4,
+  kMkvChapterStringUID = 0x5654,
+  kMkvChapterTimeStart = 0x91,
+  kMkvChapterTimeEnd = 0x92,
+  kMkvChapterDisplay = 0x80,
+  kMkvChapString = 0x85,
+  kMkvChapLanguage = 0x437C,
+  kMkvChapCountry = 0x437E,
+  // Tags
+  kMkvTags = 0x1254C367,
+  kMkvTag = 0x7373,
+  kMkvSimpleTag = 0x67C8,
+  kMkvTagName = 0x45A3,
+  kMkvTagString = 0x4487
+};
+
+}  // namespace libwebm
+
+#endif  // COMMON_WEBMIDS_H_
diff --git a/thirdparty/libsimplewebm/libwebm/mkvmuxer/mkvmuxertypes.h b/thirdparty/libsimplewebm/libwebm/mkvmuxer/mkvmuxertypes.h
new file mode 100644
index 0000000000..e5db121605
--- /dev/null
+++ b/thirdparty/libsimplewebm/libwebm/mkvmuxer/mkvmuxertypes.h
@@ -0,0 +1,28 @@
+// Copyright (c) 2012 The WebM project authors. All Rights Reserved.
+//
+// Use of this source code is governed by a BSD-style license
+// that can be found in the LICENSE file in the root of the source
+// tree. An additional intellectual property rights grant can be found
+// in the file PATENTS.  All contributing project authors may
+// be found in the AUTHORS file in the root of the source tree.
+
+#ifndef MKVMUXER_MKVMUXERTYPES_H_
+#define MKVMUXER_MKVMUXERTYPES_H_
+
+namespace mkvmuxer {
+typedef unsigned char uint8;
+typedef short int16;
+typedef int int32;
+typedef unsigned int uint32;
+typedef long long int64;
+typedef unsigned long long uint64;
+}  // namespace mkvmuxer
+
+// Copied from Chromium basictypes.h
+// A macro to disallow the copy constructor and operator= functions
+// This should be used in the private: declarations for a class
+#define LIBWEBM_DISALLOW_COPY_AND_ASSIGN(TypeName) \
+  TypeName(const TypeName&);                       \
+  void operator=(const TypeName&)
+
+#endif  // MKVMUXER_MKVMUXERTYPES_HPP_
diff --git a/thirdparty/libsimplewebm/libwebm/mkvparser/mkvparser.cc b/thirdparty/libsimplewebm/libwebm/mkvparser/mkvparser.cc
new file mode 100644
index 0000000000..bda67a5758
--- /dev/null
+++ b/thirdparty/libsimplewebm/libwebm/mkvparser/mkvparser.cc
@@ -0,0 +1,7831 @@
+// Copyright (c) 2012 The WebM project authors. All Rights Reserved.
+//
+// Use of this source code is governed by a BSD-style license
+// that can be found in the LICENSE file in the root of the source
+// tree. An additional intellectual property rights grant can be found
+// in the file PATENTS.  All contributing project authors may
+// be found in the AUTHORS file in the root of the source tree.
+#include "mkvparser/mkvparser.h"
+
+#if defined(_MSC_VER) && _MSC_VER < 1800
+#include <float.h>  // _isnan() / _finite()
+#define MSC_COMPAT
+#endif
+
+#include <assert.h>
+#include <float.h>
+#include <limits.h>
+#include <math.h>
+#include <string.h>
+
+#include "common/webmids.h"
+
+namespace mkvparser {
+const float MasteringMetadata::kValueNotPresent = FLT_MAX;
+const long long Colour::kValueNotPresent = LLONG_MAX;
+
+#ifdef MSC_COMPAT
+inline bool isnan(double val) { return !!_isnan(val); }
+inline bool isinf(double val) { return !_finite(val); }
+#endif  // MSC_COMPAT
+
+template<typename T>
+class my_auto_ptr {
+  my_auto_ptr(const my_auto_ptr &);
+  T *operator =(const my_auto_ptr &);
+
+  T *m_ptr;
+public:
+  my_auto_ptr(T *ptr) :
+    m_ptr(ptr)
+  {}
+  my_auto_ptr() :
+    m_ptr(NULL)
+  {}
+  ~my_auto_ptr() {
+    delete m_ptr;
+  }
+
+  T *release() {
+    T *ptr = m_ptr;
+    m_ptr = NULL;
+    return ptr;
+  }
+
+  T *operator ->() const {
+    return m_ptr;
+  }
+};
+
+IMkvReader::~IMkvReader() {}
+
+template <typename Type>
+Type* SafeArrayAlloc(unsigned long long num_elements,
+                     unsigned long long element_size) {
+  if (num_elements == 0 || element_size == 0)
+    return NULL;
+
+  const size_t kMaxAllocSize = 0x80000000;  // 2GiB
+  const unsigned long long num_bytes = num_elements * element_size;
+  if (element_size > (kMaxAllocSize / num_elements))
+    return NULL;
+  if (num_bytes != static_cast<size_t>(num_bytes))
+    return NULL;
+
+  return new Type[static_cast<size_t>(num_bytes)];
+}
+
+void GetVersion(int& major, int& minor, int& build, int& revision) {
+  major = 1;
+  minor = 0;
+  build = 0;
+  revision = 30;
+}
+
+long long ReadUInt(IMkvReader* pReader, long long pos, long& len) {
+  if (!pReader || pos < 0)
+    return E_FILE_FORMAT_INVALID;
+
+  len = 1;
+  unsigned char b;
+  int status = pReader->Read(pos, 1, &b);
+
+  if (status < 0)  // error or underflow
+    return status;
+
+  if (status > 0)  // interpreted as "underflow"
+    return E_BUFFER_NOT_FULL;
+
+  if (b == 0)  // we can't handle u-int values larger than 8 bytes
+    return E_FILE_FORMAT_INVALID;
+
+  unsigned char m = 0x80;
+
+  while (!(b & m)) {
+    m >>= 1;
+    ++len;
+  }
+
+  long long result = b & (~m);
+  ++pos;
+
+  for (int i = 1; i < len; ++i) {
+    status = pReader->Read(pos, 1, &b);
+
+    if (status < 0) {
+      len = 1;
+      return status;
+    }
+
+    if (status > 0) {
+      len = 1;
+      return E_BUFFER_NOT_FULL;
+    }
+
+    result <<= 8;
+    result |= b;
+
+    ++pos;
+  }
+
+  return result;
+}
+
+// Reads an EBML ID and returns it.
+// An ID must at least 1 byte long, cannot exceed 4, and its value must be
+// greater than 0.
+// See known EBML values and EBMLMaxIDLength:
+// http://www.matroska.org/technical/specs/index.html
+// Returns the ID, or a value less than 0 to report an error while reading the
+// ID.
+long long ReadID(IMkvReader* pReader, long long pos, long& len) {
+  if (pReader == NULL || pos < 0)
+    return E_FILE_FORMAT_INVALID;
+
+  // Read the first byte. The length in bytes of the ID is determined by
+  // finding the first set bit in the first byte of the ID.
+  unsigned char temp_byte = 0;
+  int read_status = pReader->Read(pos, 1, &temp_byte);
+
+  if (read_status < 0)
+    return E_FILE_FORMAT_INVALID;
+  else if (read_status > 0)  // No data to read.
+    return E_BUFFER_NOT_FULL;
+
+  if (temp_byte == 0)  // ID length > 8 bytes; invalid file.
+    return E_FILE_FORMAT_INVALID;
+
+  int bit_pos = 0;
+  const int kMaxIdLengthInBytes = 4;
+  const int kCheckByte = 0x80;
+
+  // Find the first bit that's set.
+  bool found_bit = false;
+  for (; bit_pos < kMaxIdLengthInBytes; ++bit_pos) {
+    if ((kCheckByte >> bit_pos) & temp_byte) {
+      found_bit = true;
+      break;
+    }
+  }
+
+  if (!found_bit) {
+    // The value is too large to be a valid ID.
+    return E_FILE_FORMAT_INVALID;
+  }
+
+  // Read the remaining bytes of the ID (if any).
+  const int id_length = bit_pos + 1;
+  long long ebml_id = temp_byte;
+  for (int i = 1; i < id_length; ++i) {
+    ebml_id <<= 8;
+    read_status = pReader->Read(pos + i, 1, &temp_byte);
+
+    if (read_status < 0)
+      return E_FILE_FORMAT_INVALID;
+    else if (read_status > 0)
+      return E_BUFFER_NOT_FULL;
+
+    ebml_id |= temp_byte;
+  }
+
+  len = id_length;
+  return ebml_id;
+}
+
+long long GetUIntLength(IMkvReader* pReader, long long pos, long& len) {
+  if (!pReader || pos < 0)
+    return E_FILE_FORMAT_INVALID;
+
+  long long total, available;
+
+  int status = pReader->Length(&total, &available);
+  if (status < 0 || (total >= 0 && available > total))
+    return E_FILE_FORMAT_INVALID;
+
+  len = 1;
+
+  if (pos >= available)
+    return pos;  // too few bytes available
+
+  unsigned char b;
+
+  status = pReader->Read(pos, 1, &b);
+
+  if (status != 0)
+    return status;
+
+  if (b == 0)  // we can't handle u-int values larger than 8 bytes
+    return E_FILE_FORMAT_INVALID;
+
+  unsigned char m = 0x80;
+
+  while (!(b & m)) {
+    m >>= 1;
+    ++len;
+  }
+
+  return 0;  // success
+}
+
+// TODO(vigneshv): This function assumes that unsigned values never have their
+// high bit set.
+long long UnserializeUInt(IMkvReader* pReader, long long pos, long long size) {
+  if (!pReader || pos < 0 || (size <= 0) || (size > 8))
+    return E_FILE_FORMAT_INVALID;
+
+  long long result = 0;
+
+  for (long long i = 0; i < size; ++i) {
+    unsigned char b;
+
+    const long status = pReader->Read(pos, 1, &b);
+
+    if (status < 0)
+      return status;
+
+    result <<= 8;
+    result |= b;
+
+    ++pos;
+  }
+
+  return result;
+}
+
+long UnserializeFloat(IMkvReader* pReader, long long pos, long long size_,
+                      double& result) {
+  if (!pReader || pos < 0 || ((size_ != 4) && (size_ != 8)))
+    return E_FILE_FORMAT_INVALID;
+
+  const long size = static_cast<long>(size_);
+
+  unsigned char buf[8];
+
+  const int status = pReader->Read(pos, size, buf);
+
+  if (status < 0)  // error
+    return status;
+
+  if (size == 4) {
+    union {
+      float f;
+      unsigned long ff;
+    };
+
+    ff = 0;
+
+    for (int i = 0;;) {
+      ff |= buf[i];
+
+      if (++i >= 4)
+        break;
+
+      ff <<= 8;
+    }
+
+    result = f;
+  } else {
+    union {
+      double d;
+      unsigned long long dd;
+    };
+
+    dd = 0;
+
+    for (int i = 0;;) {
+      dd |= buf[i];
+
+      if (++i >= 8)
+        break;
+
+      dd <<= 8;
+    }
+
+    result = d;
+  }
+
+  if (isinf(result) || isnan(result))
+    return E_FILE_FORMAT_INVALID;
+
+  return 0;
+}
+
+long UnserializeInt(IMkvReader* pReader, long long pos, long long size,
+                    long long& result_ref) {
+  if (!pReader || pos < 0 || size < 1 || size > 8)
+    return E_FILE_FORMAT_INVALID;
+
+  signed char first_byte = 0;
+  const long status = pReader->Read(pos, 1, (unsigned char*)&first_byte);
+
+  if (status < 0)
+    return status;
+
+  unsigned long long result = first_byte;
+  ++pos;
+
+  for (long i = 1; i < size; ++i) {
+    unsigned char b;
+
+    const long status = pReader->Read(pos, 1, &b);
+
+    if (status < 0)
+      return status;
+
+    result <<= 8;
+    result |= b;
+
+    ++pos;
+  }
+
+  result_ref = static_cast<long long>(result);
+  return 0;
+}
+
+long UnserializeString(IMkvReader* pReader, long long pos, long long size,
+                       char*& str) {
+  delete[] str;
+  str = NULL;
+
+  if (size >= LONG_MAX || size < 0)
+    return E_FILE_FORMAT_INVALID;
+
+  // +1 for '\0' terminator
+  const long required_size = static_cast<long>(size) + 1;
+
+  str = SafeArrayAlloc<char>(1, required_size);
+  if (str == NULL)
+    return E_FILE_FORMAT_INVALID;
+
+  unsigned char* const buf = reinterpret_cast<unsigned char*>(str);
+
+  const long status = pReader->Read(pos, static_cast<long>(size), buf);
+
+  if (status) {
+    delete[] str;
+    str = NULL;
+
+    return status;
+  }
+
+  str[required_size - 1] = '\0';
+  return 0;
+}
+
+long ParseElementHeader(IMkvReader* pReader, long long& pos, long long stop,
+                        long long& id, long long& size) {
+  if (stop >= 0 && pos >= stop)
+    return E_FILE_FORMAT_INVALID;
+
+  long len;
+
+  id = ReadID(pReader, pos, len);
+
+  if (id < 0)
+    return E_FILE_FORMAT_INVALID;
+
+  pos += len;  // consume id
+
+  if (stop >= 0 && pos >= stop)
+    return E_FILE_FORMAT_INVALID;
+
+  size = ReadUInt(pReader, pos, len);
+
+  if (size < 0 || len < 1 || len > 8) {
+    // Invalid: Negative payload size, negative or 0 length integer, or integer
+    // larger than 64 bits (libwebm cannot handle them).
+    return E_FILE_FORMAT_INVALID;
+  }
+
+  // Avoid rolling over pos when very close to LLONG_MAX.
+  const unsigned long long rollover_check =
+      static_cast<unsigned long long>(pos) + len;
+  if (rollover_check > LLONG_MAX)
+    return E_FILE_FORMAT_INVALID;
+
+  pos += len;  // consume length of size
+
+  // pos now designates payload
+
+  if (stop >= 0 && pos > stop)
+    return E_FILE_FORMAT_INVALID;
+
+  return 0;  // success
+}
+
+bool Match(IMkvReader* pReader, long long& pos, unsigned long expected_id,
+           long long& val) {
+  if (!pReader || pos < 0)
+    return false;
+
+  long long total = 0;
+  long long available = 0;
+
+  const long status = pReader->Length(&total, &available);
+  if (status < 0 || (total >= 0 && available > total))
+    return false;
+
+  long len = 0;
+
+  const long long id = ReadID(pReader, pos, len);
+  if (id < 0 || (available - pos) > len)
+    return false;
+
+  if (static_cast<unsigned long>(id) != expected_id)
+    return false;
+
+  pos += len;  // consume id
+
+  const long long size = ReadUInt(pReader, pos, len);
+  if (size < 0 || size > 8 || len < 1 || len > 8 || (available - pos) > len)
+    return false;
+
+  pos += len;  // consume length of size of payload
+
+  val = UnserializeUInt(pReader, pos, size);
+  if (val < 0)
+    return false;
+
+  pos += size;  // consume size of payload
+
+  return true;
+}
+
+bool Match(IMkvReader* pReader, long long& pos, unsigned long expected_id,
+           unsigned char*& buf, size_t& buflen) {
+  if (!pReader || pos < 0)
+    return false;
+
+  long long total = 0;
+  long long available = 0;
+
+  long status = pReader->Length(&total, &available);
+  if (status < 0 || (total >= 0 && available > total))
+    return false;
+
+  long len = 0;
+  const long long id = ReadID(pReader, pos, len);
+  if (id < 0 || (available - pos) > len)
+    return false;
+
+  if (static_cast<unsigned long>(id) != expected_id)
+    return false;
+
+  pos += len;  // consume id
+
+  const long long size = ReadUInt(pReader, pos, len);
+  if (size < 0 || len <= 0 || len > 8 || (available - pos) > len)
+    return false;
+
+  unsigned long long rollover_check =
+      static_cast<unsigned long long>(pos) + len;
+  if (rollover_check > LLONG_MAX)
+    return false;
+
+  pos += len;  // consume length of size of payload
+
+  rollover_check = static_cast<unsigned long long>(pos) + size;
+  if (rollover_check > LLONG_MAX)
+    return false;
+
+  if ((pos + size) > available)
+    return false;
+
+  if (size >= LONG_MAX)
+    return false;
+
+  const long buflen_ = static_cast<long>(size);
+
+  buf = SafeArrayAlloc<unsigned char>(1, buflen_);
+  if (!buf)
+    return false;
+
+  status = pReader->Read(pos, buflen_, buf);
+  if (status != 0)
+    return false;
+
+  buflen = buflen_;
+
+  pos += size;  // consume size of payload
+  return true;
+}
+
+EBMLHeader::EBMLHeader() : m_docType(NULL) { Init(); }
+
+EBMLHeader::~EBMLHeader() { delete[] m_docType; }
+
+void EBMLHeader::Init() {
+  m_version = 1;
+  m_readVersion = 1;
+  m_maxIdLength = 4;
+  m_maxSizeLength = 8;
+
+  if (m_docType) {
+    delete[] m_docType;
+    m_docType = NULL;
+  }
+
+  m_docTypeVersion = 1;
+  m_docTypeReadVersion = 1;
+}
+
+long long EBMLHeader::Parse(IMkvReader* pReader, long long& pos) {
+  if (!pReader)
+    return E_FILE_FORMAT_INVALID;
+
+  long long total, available;
+
+  long status = pReader->Length(&total, &available);
+
+  if (status < 0)  // error
+    return status;
+
+  pos = 0;
+
+  // Scan until we find what looks like the first byte of the EBML header.
+  const long long kMaxScanBytes = (available >= 1024) ? 1024 : available;
+  const unsigned char kEbmlByte0 = 0x1A;
+  unsigned char scan_byte = 0;
+
+  while (pos < kMaxScanBytes) {
+    status = pReader->Read(pos, 1, &scan_byte);
+
+    if (status < 0)  // error
+      return status;
+    else if (status > 0)
+      return E_BUFFER_NOT_FULL;
+
+    if (scan_byte == kEbmlByte0)
+      break;
+
+    ++pos;
+  }
+
+  long len = 0;
+  const long long ebml_id = ReadID(pReader, pos, len);
+
+  if (ebml_id == E_BUFFER_NOT_FULL)
+    return E_BUFFER_NOT_FULL;
+
+  if (len != 4 || ebml_id != libwebm::kMkvEBML)
+    return E_FILE_FORMAT_INVALID;
+
+  // Move read pos forward to the EBML header size field.
+  pos += 4;
+
+  // Read length of size field.
+  long long result = GetUIntLength(pReader, pos, len);
+
+  if (result < 0)  // error
+    return E_FILE_FORMAT_INVALID;
+  else if (result > 0)  // need more data
+    return E_BUFFER_NOT_FULL;
+
+  if (len < 1 || len > 8)
+    return E_FILE_FORMAT_INVALID;
+
+  if ((total >= 0) && ((total - pos) < len))
+    return E_FILE_FORMAT_INVALID;
+
+  if ((available - pos) < len)
+    return pos + len;  // try again later
+
+  // Read the EBML header size.
+  result = ReadUInt(pReader, pos, len);
+
+  if (result < 0)  // error
+    return result;
+
+  pos += len;  // consume size field
+
+  // pos now designates start of payload
+
+  if ((total >= 0) && ((total - pos) < result))
+    return E_FILE_FORMAT_INVALID;
+
+  if ((available - pos) < result)
+    return pos + result;
+
+  const long long end = pos + result;
+
+  Init();
+
+  while (pos < end) {
+    long long id, size;
+
+    status = ParseElementHeader(pReader, pos, end, id, size);
+
+    if (status < 0)  // error
+      return status;
+
+    if (size == 0)
+      return E_FILE_FORMAT_INVALID;
+
+    if (id == libwebm::kMkvEBMLVersion) {
+      m_version = UnserializeUInt(pReader, pos, size);
+
+      if (m_version <= 0)
+        return E_FILE_FORMAT_INVALID;
+    } else if (id == libwebm::kMkvEBMLReadVersion) {
+      m_readVersion = UnserializeUInt(pReader, pos, size);
+
+      if (m_readVersion <= 0)
+        return E_FILE_FORMAT_INVALID;
+    } else if (id == libwebm::kMkvEBMLMaxIDLength) {
+      m_maxIdLength = UnserializeUInt(pReader, pos, size);
+
+      if (m_maxIdLength <= 0)
+        return E_FILE_FORMAT_INVALID;
+    } else if (id == libwebm::kMkvEBMLMaxSizeLength) {
+      m_maxSizeLength = UnserializeUInt(pReader, pos, size);
+
+      if (m_maxSizeLength <= 0)
+        return E_FILE_FORMAT_INVALID;
+    } else if (id == libwebm::kMkvDocType) {
+      if (m_docType)
+        return E_FILE_FORMAT_INVALID;
+
+      status = UnserializeString(pReader, pos, size, m_docType);
+
+      if (status)  // error
+        return status;
+    } else if (id == libwebm::kMkvDocTypeVersion) {
+      m_docTypeVersion = UnserializeUInt(pReader, pos, size);
+
+      if (m_docTypeVersion <= 0)
+        return E_FILE_FORMAT_INVALID;
+    } else if (id == libwebm::kMkvDocTypeReadVersion) {
+      m_docTypeReadVersion = UnserializeUInt(pReader, pos, size);
+
+      if (m_docTypeReadVersion <= 0)
+        return E_FILE_FORMAT_INVALID;
+    }
+
+    pos += size;
+  }
+
+  if (pos != end)
+    return E_FILE_FORMAT_INVALID;
+
+  // Make sure DocType, DocTypeReadVersion, and DocTypeVersion are valid.
+  if (m_docType == NULL || m_docTypeReadVersion <= 0 || m_docTypeVersion <= 0)
+    return E_FILE_FORMAT_INVALID;
+
+  // Make sure EBMLMaxIDLength and EBMLMaxSizeLength are valid.
+  if (m_maxIdLength <= 0 || m_maxIdLength > 4 || m_maxSizeLength <= 0 ||
+      m_maxSizeLength > 8)
+    return E_FILE_FORMAT_INVALID;
+
+  return 0;
+}
+
+Segment::Segment(IMkvReader* pReader, long long elem_start,
+                 // long long elem_size,
+                 long long start, long long size)
+    : m_pReader(pReader),
+      m_element_start(elem_start),
+      // m_element_size(elem_size),
+      m_start(start),
+      m_size(size),
+      m_pos(start),
+      m_pUnknownSize(0),
+      m_pSeekHead(NULL),
+      m_pInfo(NULL),
+      m_pTracks(NULL),
+      m_pCues(NULL),
+      m_pChapters(NULL),
+      m_pTags(NULL),
+      m_clusters(NULL),
+      m_clusterCount(0),
+      m_clusterPreloadCount(0),
+      m_clusterSize(0) {}
+
+Segment::~Segment() {
+  const long count = m_clusterCount + m_clusterPreloadCount;
+
+  Cluster** i = m_clusters;
+  Cluster** j = m_clusters + count;
+
+  while (i != j) {
+    Cluster* const p = *i++;
+    delete p;
+  }
+
+  delete[] m_clusters;
+
+  delete m_pTracks;
+  delete m_pInfo;
+  delete m_pCues;
+  delete m_pChapters;
+  delete m_pTags;
+  delete m_pSeekHead;
+}
+
+long long Segment::CreateInstance(IMkvReader* pReader, long long pos,
+                                  Segment*& pSegment) {
+  if (pReader == NULL || pos < 0)
+    return E_PARSE_FAILED;
+
+  pSegment = NULL;
+
+  long long total, available;
+
+  const long status = pReader->Length(&total, &available);
+
+  if (status < 0)  // error
+    return status;
+
+  if (available < 0)
+    return -1;
+
+  if ((total >= 0) && (available > total))
+    return -1;
+
+  // I would assume that in practice this loop would execute
+  // exactly once, but we allow for other elements (e.g. Void)
+  // to immediately follow the EBML header.  This is fine for
+  // the source filter case (since the entire file is available),
+  // but in the splitter case over a network we should probably
+  // just give up early.  We could for example decide only to
+  // execute this loop a maximum of, say, 10 times.
+  // TODO:
+  // There is an implied "give up early" by only parsing up
+  // to the available limit.  We do do that, but only if the
+  // total file size is unknown.  We could decide to always
+  // use what's available as our limit (irrespective of whether
+  // we happen to know the total file length).  This would have
+  // as its sense "parse this much of the file before giving up",
+  // which a slightly different sense from "try to parse up to
+  // 10 EMBL elements before giving up".
+
+  for (;;) {
+    if ((total >= 0) && (pos >= total))
+      return E_FILE_FORMAT_INVALID;
+
+    // Read ID
+    long len;
+    long long result = GetUIntLength(pReader, pos, len);
+
+    if (result)  // error, or too few available bytes
+      return result;
+
+    if ((total >= 0) && ((pos + len) > total))
+      return E_FILE_FORMAT_INVALID;
+
+    if ((pos + len) > available)
+      return pos + len;
+
+    const long long idpos = pos;
+    const long long id = ReadID(pReader, pos, len);
+
+    if (id < 0)
+      return E_FILE_FORMAT_INVALID;
+
+    pos += len;  // consume ID
+
+    // Read Size
+
+    result = GetUIntLength(pReader, pos, len);
+
+    if (result)  // error, or too few available bytes
+      return result;
+
+    if ((total >= 0) && ((pos + len) > total))
+      return E_FILE_FORMAT_INVALID;
+
+    if ((pos + len) > available)
+      return pos + len;
+
+    long long size = ReadUInt(pReader, pos, len);
+
+    if (size < 0)  // error
+      return size;
+
+    pos += len;  // consume length of size of element
+
+    // Pos now points to start of payload
+
+    // Handle "unknown size" for live streaming of webm files.
+    const long long unknown_size = (1LL << (7 * len)) - 1;
+
+    if (id == libwebm::kMkvSegment) {
+      if (size == unknown_size)
+        size = -1;
+
+      else if (total < 0)
+        size = -1;
+
+      else if ((pos + size) > total)
+        size = -1;
+
+      pSegment = new Segment(pReader, idpos, pos, size);
+
+      return 0;  // success
+    }
+
+    if (size == unknown_size)
+      return E_FILE_FORMAT_INVALID;
+
+    if ((total >= 0) && ((pos + size) > total))
+      return E_FILE_FORMAT_INVALID;
+
+    if ((pos + size) > available)
+      return pos + size;
+
+    pos += size;  // consume payload
+  }
+}
+
+long long Segment::ParseHeaders() {
+  // Outermost (level 0) segment object has been constructed,
+  // and pos designates start of payload.  We need to find the
+  // inner (level 1) elements.
+  long long total, available;
+
+  const int status = m_pReader->Length(&total, &available);
+
+  if (status < 0)  // error
+    return status;
+
+  if (total > 0 && available > total)
+    return E_FILE_FORMAT_INVALID;
+
+  const long long segment_stop = (m_size < 0) ? -1 : m_start + m_size;
+
+  if ((segment_stop >= 0 && total >= 0 && segment_stop > total) ||
+      (segment_stop >= 0 && m_pos > segment_stop)) {
+    return E_FILE_FORMAT_INVALID;
+  }
+
+  for (;;) {
+    if ((total >= 0) && (m_pos >= total))
+      break;
+
+    if ((segment_stop >= 0) && (m_pos >= segment_stop))
+      break;
+
+    long long pos = m_pos;
+    const long long element_start = pos;
+
+    // Avoid rolling over pos when very close to LLONG_MAX.
+    unsigned long long rollover_check = pos + 1ULL;
+    if (rollover_check > LLONG_MAX)
+      return E_FILE_FORMAT_INVALID;
+
+    if ((pos + 1) > available)
+      return (pos + 1);
+
+    long len;
+    long long result = GetUIntLength(m_pReader, pos, len);
+
+    if (result < 0)  // error
+      return result;
+
+    if (result > 0) {
+      // MkvReader doesn't have enough data to satisfy this read attempt.
+      return (pos + 1);
+    }
+
+    if ((segment_stop >= 0) && ((pos + len) > segment_stop))
+      return E_FILE_FORMAT_INVALID;
+
+    if ((pos + len) > available)
+      return pos + len;
+
+    const long long idpos = pos;
+    const long long id = ReadID(m_pReader, idpos, len);
+
+    if (id < 0)
+      return E_FILE_FORMAT_INVALID;
+
+    if (id == libwebm::kMkvCluster)
+      break;
+
+    pos += len;  // consume ID
+
+    if ((pos + 1) > available)
+      return (pos + 1);
+
+    // Read Size
+    result = GetUIntLength(m_pReader, pos, len);
+
+    if (result < 0)  // error
+      return result;
+
+    if (result > 0) {
+      // MkvReader doesn't have enough data to satisfy this read attempt.
+      return (pos + 1);
+    }
+
+    if ((segment_stop >= 0) && ((pos + len) > segment_stop))
+      return E_FILE_FORMAT_INVALID;
+
+    if ((pos + len) > available)
+      return pos + len;
+
+    const long long size = ReadUInt(m_pReader, pos, len);
+
+    if (size < 0 || len < 1 || len > 8) {
+      // TODO(tomfinegan): ReadUInt should return an error when len is < 1 or
+      // len > 8 is true instead of checking this _everywhere_.
+      return size;
+    }
+
+    pos += len;  // consume length of size of element
+
+    // Avoid rolling over pos when very close to LLONG_MAX.
+    rollover_check = static_cast<unsigned long long>(pos) + size;
+    if (rollover_check > LLONG_MAX)
+      return E_FILE_FORMAT_INVALID;
+
+    const long long element_size = size + pos - element_start;
+
+    // Pos now points to start of payload
+
+    if ((segment_stop >= 0) && ((pos + size) > segment_stop))
+      return E_FILE_FORMAT_INVALID;
+
+    // We read EBML elements either in total or nothing at all.
+
+    if ((pos + size) > available)
+      return pos + size;
+
+    if (id == libwebm::kMkvInfo) {
+      if (m_pInfo)
+        return E_FILE_FORMAT_INVALID;
+
+      m_pInfo = new SegmentInfo(this, pos, size, element_start, element_size);
+
+      const long status = m_pInfo->Parse();
+
+      if (status)
+        return status;
+    } else if (id == libwebm::kMkvTracks) {
+      if (m_pTracks)
+        return E_FILE_FORMAT_INVALID;
+
+      m_pTracks = new Tracks(this, pos, size, element_start, element_size);
+
+      const long status = m_pTracks->Parse();
+
+      if (status)
+        return status;
+    } else if (id == libwebm::kMkvCues) {
+      if (m_pCues == NULL) {
+        m_pCues = new Cues(this, pos, size, element_start, element_size);
+      }
+    } else if (id == libwebm::kMkvSeekHead) {
+      if (m_pSeekHead == NULL) {
+        m_pSeekHead = new SeekHead(this, pos, size, element_start, element_size);
+
+        const long status = m_pSeekHead->Parse();
+
+        if (status)
+          return status;
+      }
+    } else if (id == libwebm::kMkvChapters) {
+      if (m_pChapters == NULL) {
+        m_pChapters = new Chapters(this, pos, size, element_start, element_size);
+
+        const long status = m_pChapters->Parse();
+
+        if (status)
+          return status;
+      }
+    } else if (id == libwebm::kMkvTags) {
+      if (m_pTags == NULL) {
+        m_pTags = new Tags(this, pos, size, element_start, element_size);
+
+        const long status = m_pTags->Parse();
+
+        if (status)
+          return status;
+      }
+    }
+
+    m_pos = pos + size;  // consume payload
+  }
+
+  if (segment_stop >= 0 && m_pos > segment_stop)
+    return E_FILE_FORMAT_INVALID;
+
+  if (m_pInfo == NULL)  // TODO: liberalize this behavior
+    return E_FILE_FORMAT_INVALID;
+
+  if (m_pTracks == NULL)
+    return E_FILE_FORMAT_INVALID;
+
+  return 0;  // success
+}
+
+long Segment::LoadCluster(long long& pos, long& len) {
+  for (;;) {
+    const long result = DoLoadCluster(pos, len);
+
+    if (result <= 1)
+      return result;
+  }
+}
+
+long Segment::DoLoadCluster(long long& pos, long& len) {
+  if (m_pos < 0)
+    return DoLoadClusterUnknownSize(pos, len);
+
+  long long total, avail;
+
+  long status = m_pReader->Length(&total, &avail);
+
+  if (status < 0)  // error
+    return status;
+
+  if (total >= 0 && avail > total)
+    return E_FILE_FORMAT_INVALID;
+
+  const long long segment_stop = (m_size < 0) ? -1 : m_start + m_size;
+
+  long long cluster_off = -1;  // offset relative to start of segment
+  long long cluster_size = -1;  // size of cluster payload
+
+  for (;;) {
+    if ((total >= 0) && (m_pos >= total))
+      return 1;  // no more clusters
+
+    if ((segment_stop >= 0) && (m_pos >= segment_stop))
+      return 1;  // no more clusters
+
+    pos = m_pos;
+
+    // Read ID
+
+    if ((pos + 1) > avail) {
+      len = 1;
+      return E_BUFFER_NOT_FULL;
+    }
+
+    long long result = GetUIntLength(m_pReader, pos, len);
+
+    if (result < 0)  // error
+      return static_cast<long>(result);
+
+    if (result > 0)
+      return E_BUFFER_NOT_FULL;
+
+    if ((segment_stop >= 0) && ((pos + len) > segment_stop))
+      return E_FILE_FORMAT_INVALID;
+
+    if ((pos + len) > avail)
+      return E_BUFFER_NOT_FULL;
+
+    const long long idpos = pos;
+    const long long id = ReadID(m_pReader, idpos, len);
+
+    if (id < 0)
+      return E_FILE_FORMAT_INVALID;
+
+    pos += len;  // consume ID
+
+    // Read Size
+
+    if ((pos + 1) > avail) {
+      len = 1;
+      return E_BUFFER_NOT_FULL;
+    }
+
+    result = GetUIntLength(m_pReader, pos, len);
+
+    if (result < 0)  // error
+      return static_cast<long>(result);
+
+    if (result > 0)
+      return E_BUFFER_NOT_FULL;
+
+    if ((segment_stop >= 0) && ((pos + len) > segment_stop))
+      return E_FILE_FORMAT_INVALID;
+
+    if ((pos + len) > avail)
+      return E_BUFFER_NOT_FULL;
+
+    const long long size = ReadUInt(m_pReader, pos, len);
+
+    if (size < 0)  // error
+      return static_cast<long>(size);
+
+    pos += len;  // consume length of size of element
+
+    // pos now points to start of payload
+
+    if (size == 0) {
+      // Missing element payload: move on.
+      m_pos = pos;
+      continue;
+    }
+
+    const long long unknown_size = (1LL << (7 * len)) - 1;
+
+    if ((segment_stop >= 0) && (size != unknown_size) &&
+        ((pos + size) > segment_stop)) {
+      return E_FILE_FORMAT_INVALID;
+    }
+
+    if (id == libwebm::kMkvCues) {
+      if (size == unknown_size) {
+        // Cues element of unknown size: Not supported.
+        return E_FILE_FORMAT_INVALID;
+      }
+
+      if (m_pCues == NULL) {
+        const long long element_size = (pos - idpos) + size;
+
+        m_pCues = new Cues(this, pos, size, idpos, element_size);
+      }
+
+      m_pos = pos + size;  // consume payload
+      continue;
+    }
+
+    if (id != libwebm::kMkvCluster) {
+      // Besides the Segment, Libwebm allows only cluster elements of unknown
+      // size. Fail the parse upon encountering a non-cluster element reporting
+      // unknown size.
+      if (size == unknown_size)
+        return E_FILE_FORMAT_INVALID;
+
+      m_pos = pos + size;  // consume payload
+      continue;
+    }
+
+    // We have a cluster.
+
+    cluster_off = idpos - m_start;  // relative pos
+
+    if (size != unknown_size)
+      cluster_size = size;
+
+    break;
+  }
+
+  if (cluster_off < 0) {
+    // No cluster, die.
+    return E_FILE_FORMAT_INVALID;
+  }
+
+  long long pos_;
+  long len_;
+
+  status = Cluster::HasBlockEntries(this, cluster_off, pos_, len_);
+
+  if (status < 0) {  // error, or underflow
+    pos = pos_;
+    len = len_;
+
+    return status;
+  }
+
+  // status == 0 means "no block entries found"
+  // status > 0 means "found at least one block entry"
+
+  // TODO:
+  // The issue here is that the segment increments its own
+  // pos ptr past the most recent cluster parsed, and then
+  // starts from there to parse the next cluster.  If we
+  // don't know the size of the current cluster, then we
+  // must either parse its payload (as we do below), looking
+  // for the cluster (or cues) ID to terminate the parse.
+  // This isn't really what we want: rather, we really need
+  // a way to create the curr cluster object immediately.
+  // The pity is that cluster::parse can determine its own
+  // boundary, and we largely duplicate that same logic here.
+  //
+  // Maybe we need to get rid of our look-ahead preloading
+  // in source::parse???
+  //
+  // As we're parsing the blocks in the curr cluster
+  //(in cluster::parse), we should have some way to signal
+  // to the segment that we have determined the boundary,
+  // so it can adjust its own segment::m_pos member.
+  //
+  // The problem is that we're asserting in asyncreadinit,
+  // because we adjust the pos down to the curr seek pos,
+  // and the resulting adjusted len is > 2GB.  I'm suspicious
+  // that this is even correct, but even if it is, we can't
+  // be loading that much data in the cache anyway.
+
+  const long idx = m_clusterCount;
+
+  if (m_clusterPreloadCount > 0) {
+    if (idx >= m_clusterSize)
+      return E_FILE_FORMAT_INVALID;
+
+    Cluster* const pCluster = m_clusters[idx];
+    if (pCluster == NULL || pCluster->m_index >= 0)
+      return E_FILE_FORMAT_INVALID;
+
+    const long long off = pCluster->GetPosition();
+    if (off < 0)
+      return E_FILE_FORMAT_INVALID;
+
+    if (off == cluster_off) {  // preloaded already
+      if (status == 0)  // no entries found
+        return E_FILE_FORMAT_INVALID;
+
+      if (cluster_size >= 0)
+        pos += cluster_size;
+      else {
+        const long long element_size = pCluster->GetElementSize();
+
+        if (element_size <= 0)
+          return E_FILE_FORMAT_INVALID;  // TODO: handle this case
+
+        pos = pCluster->m_element_start + element_size;
+      }
+
+      pCluster->m_index = idx;  // move from preloaded to loaded
+      ++m_clusterCount;
+      --m_clusterPreloadCount;
+
+      m_pos = pos;  // consume payload
+      if (segment_stop >= 0 && m_pos > segment_stop)
+        return E_FILE_FORMAT_INVALID;
+
+      return 0;  // success
+    }
+  }
+
+  if (status == 0) {  // no entries found
+    if (cluster_size >= 0)
+      pos += cluster_size;
+
+    if ((total >= 0) && (pos >= total)) {
+      m_pos = total;
+      return 1;  // no more clusters
+    }
+
+    if ((segment_stop >= 0) && (pos >= segment_stop)) {
+      m_pos = segment_stop;
+      return 1;  // no more clusters
+    }
+
+    m_pos = pos;
+    return 2;  // try again
+  }
+
+  // status > 0 means we have an entry
+
+  Cluster* const pCluster = Cluster::Create(this, idx, cluster_off);
+  if (pCluster == NULL)
+    return -1;
+
+  if (!AppendCluster(pCluster)) {
+    delete pCluster;
+    return -1;
+  }
+
+  if (cluster_size >= 0) {
+    pos += cluster_size;
+
+    m_pos = pos;
+
+    if (segment_stop > 0 && m_pos > segment_stop)
+      return E_FILE_FORMAT_INVALID;
+
+    return 0;
+  }
+
+  m_pUnknownSize = pCluster;
+  m_pos = -pos;
+
+  return 0;  // partial success, since we have a new cluster
+
+  // status == 0 means "no block entries found"
+  // pos designates start of payload
+  // m_pos has NOT been adjusted yet (in case we need to come back here)
+}
+
+long Segment::DoLoadClusterUnknownSize(long long& pos, long& len) {
+  if (m_pos >= 0 || m_pUnknownSize == NULL)
+    return E_PARSE_FAILED;
+
+  const long status = m_pUnknownSize->Parse(pos, len);
+
+  if (status < 0)  // error or underflow
+    return status;
+
+  if (status == 0)  // parsed a block
+    return 2;  // continue parsing
+
+  const long long start = m_pUnknownSize->m_element_start;
+  const long long size = m_pUnknownSize->GetElementSize();
+
+  if (size < 0)
+    return E_FILE_FORMAT_INVALID;
+
+  pos = start + size;
+  m_pos = pos;
+
+  m_pUnknownSize = 0;
+
+  return 2;  // continue parsing
+}
+
+bool Segment::AppendCluster(Cluster* pCluster) {
+  if (pCluster == NULL || pCluster->m_index < 0)
+    return false;
+
+  const long count = m_clusterCount + m_clusterPreloadCount;
+
+  long& size = m_clusterSize;
+  const long idx = pCluster->m_index;
+
+  if (size < count || idx != m_clusterCount)
+    return false;
+
+  if (count >= size) {
+    const long n = (size <= 0) ? 2048 : 2 * size;
+
+    Cluster** const qq = new Cluster*[n];
+
+    Cluster** q = qq;
+    Cluster** p = m_clusters;
+    Cluster** const pp = p + count;
+
+    while (p != pp)
+      *q++ = *p++;
+
+    delete[] m_clusters;
+
+    m_clusters = qq;
+    size = n;
+  }
+
+  if (m_clusterPreloadCount > 0) {
+    Cluster** const p = m_clusters + m_clusterCount;
+    if (*p == NULL || (*p)->m_index >= 0)
+      return false;
+
+    Cluster** q = p + m_clusterPreloadCount;
+    if (q >= (m_clusters + size))
+      return false;
+
+    for (;;) {
+      Cluster** const qq = q - 1;
+      if ((*qq)->m_index >= 0)
+        return false;
+
+      *q = *qq;
+      q = qq;
+
+      if (q == p)
+        break;
+    }
+  }
+
+  m_clusters[idx] = pCluster;
+  ++m_clusterCount;
+  return true;
+}
+
+bool Segment::PreloadCluster(Cluster* pCluster, ptrdiff_t idx) {
+  if (pCluster == NULL || pCluster->m_index >= 0 || idx < m_clusterCount)
+    return false;
+
+  const long count = m_clusterCount + m_clusterPreloadCount;
+
+  long& size = m_clusterSize;
+  if (size < count)
+    return false;
+
+  if (count >= size) {
+    const long n = (size <= 0) ? 2048 : 2 * size;
+
+    Cluster** const qq = new Cluster*[n];
+    Cluster** q = qq;
+
+    Cluster** p = m_clusters;
+    Cluster** const pp = p + count;
+
+    while (p != pp)
+      *q++ = *p++;
+
+    delete[] m_clusters;
+
+    m_clusters = qq;
+    size = n;
+  }
+
+  if (m_clusters == NULL)
+    return false;
+
+  Cluster** const p = m_clusters + idx;
+
+  Cluster** q = m_clusters + count;
+  if (q < p || q >= (m_clusters + size))
+    return false;
+
+  while (q > p) {
+    Cluster** const qq = q - 1;
+
+    if ((*qq)->m_index >= 0)
+      return false;
+
+    *q = *qq;
+    q = qq;
+  }
+
+  m_clusters[idx] = pCluster;
+  ++m_clusterPreloadCount;
+  return true;
+}
+
+long Segment::Load() {
+  if (m_clusters != NULL || m_clusterSize != 0 || m_clusterCount != 0)
+    return E_PARSE_FAILED;
+
+  // Outermost (level 0) segment object has been constructed,
+  // and pos designates start of payload.  We need to find the
+  // inner (level 1) elements.
+
+  const long long header_status = ParseHeaders();
+
+  if (header_status < 0)  // error
+    return static_cast<long>(header_status);
+
+  if (header_status > 0)  // underflow
+    return E_BUFFER_NOT_FULL;
+
+  if (m_pInfo == NULL || m_pTracks == NULL)
+    return E_FILE_FORMAT_INVALID;
+
+  for (;;) {
+    const long status = LoadCluster();
+
+    if (status < 0)  // error
+      return status;
+
+    if (status >= 1)  // no more clusters
+      return 0;
+  }
+}
+
+SeekHead::SeekHead(Segment* pSegment, long long start, long long size_,
+                   long long element_start, long long element_size)
+    : m_pSegment(pSegment),
+      m_start(start),
+      m_size(size_),
+      m_element_start(element_start),
+      m_element_size(element_size),
+      m_entries(0),
+      m_entry_count(0),
+      m_void_elements(0),
+      m_void_element_count(0) {}
+
+SeekHead::~SeekHead() {
+  delete[] m_entries;
+  delete[] m_void_elements;
+}
+
+long SeekHead::Parse() {
+  IMkvReader* const pReader = m_pSegment->m_pReader;
+
+  long long pos = m_start;
+  const long long stop = m_start + m_size;
+
+  // first count the seek head entries
+
+  int entry_count = 0;
+  int void_element_count = 0;
+
+  while (pos < stop) {
+    long long id, size;
+
+    const long status = ParseElementHeader(pReader, pos, stop, id, size);
+
+    if (status < 0)  // error
+      return status;
+
+    if (id == libwebm::kMkvSeek)
+      ++entry_count;
+    else if (id == libwebm::kMkvVoid)
+      ++void_element_count;
+
+    pos += size;  // consume payload
+
+    if (pos > stop)
+      return E_FILE_FORMAT_INVALID;
+  }
+
+  if (pos != stop)
+    return E_FILE_FORMAT_INVALID;
+
+  m_entries = new Entry[entry_count];
+
+  m_void_elements = new VoidElement[void_element_count];
+
+  // now parse the entries and void elements
+
+  Entry* pEntry = m_entries;
+  VoidElement* pVoidElement = m_void_elements;
+
+  pos = m_start;
+
+  while (pos < stop) {
+    const long long idpos = pos;
+
+    long long id, size;
+
+    const long status = ParseElementHeader(pReader, pos, stop, id, size);
+
+    if (status < 0)  // error
+      return status;
+
+    if (id == libwebm::kMkvSeek) {
+      if (ParseEntry(pReader, pos, size, pEntry)) {
+        Entry& e = *pEntry++;
+
+        e.element_start = idpos;
+        e.element_size = (pos + size) - idpos;
+      }
+    } else if (id == libwebm::kMkvVoid) {
+      VoidElement& e = *pVoidElement++;
+
+      e.element_start = idpos;
+      e.element_size = (pos + size) - idpos;
+    }
+
+    pos += size;  // consume payload
+    if (pos > stop)
+      return E_FILE_FORMAT_INVALID;
+  }
+
+  if (pos != stop)
+    return E_FILE_FORMAT_INVALID;
+
+  ptrdiff_t count_ = ptrdiff_t(pEntry - m_entries);
+  assert(count_ >= 0);
+  assert(count_ <= entry_count);
+
+  m_entry_count = static_cast<int>(count_);
+
+  count_ = ptrdiff_t(pVoidElement - m_void_elements);
+  assert(count_ >= 0);
+  assert(count_ <= void_element_count);
+
+  m_void_element_count = static_cast<int>(count_);
+
+  return 0;
+}
+
+int SeekHead::GetCount() const { return m_entry_count; }
+
+const SeekHead::Entry* SeekHead::GetEntry(int idx) const {
+  if (idx < 0)
+    return 0;
+
+  if (idx >= m_entry_count)
+    return 0;
+
+  return m_entries + idx;
+}
+
+int SeekHead::GetVoidElementCount() const { return m_void_element_count; }
+
+const SeekHead::VoidElement* SeekHead::GetVoidElement(int idx) const {
+  if (idx < 0)
+    return 0;
+
+  if (idx >= m_void_element_count)
+    return 0;
+
+  return m_void_elements + idx;
+}
+
+long Segment::ParseCues(long long off, long long& pos, long& len) {
+  if (m_pCues)
+    return 0;  // success
+
+  if (off < 0)
+    return -1;
+
+  long long total, avail;
+
+  const int status = m_pReader->Length(&total, &avail);
+
+  if (status < 0)  // error
+    return status;
+
+  assert((total < 0) || (avail <= total));
+
+  pos = m_start + off;
+
+  if ((total < 0) || (pos >= total))
+    return 1;  // don't bother parsing cues
+
+  const long long element_start = pos;
+  const long long segment_stop = (m_size < 0) ? -1 : m_start + m_size;
+
+  if ((pos + 1) > avail) {
+    len = 1;
+    return E_BUFFER_NOT_FULL;
+  }
+
+  long long result = GetUIntLength(m_pReader, pos, len);
+
+  if (result < 0)  // error
+    return static_cast<long>(result);
+
+  if (result > 0)  // underflow (weird)
+  {
+    len = 1;
+    return E_BUFFER_NOT_FULL;
+  }
+
+  if ((segment_stop >= 0) && ((pos + len) > segment_stop))
+    return E_FILE_FORMAT_INVALID;
+
+  if ((pos + len) > avail)
+    return E_BUFFER_NOT_FULL;
+
+  const long long idpos = pos;
+
+  const long long id = ReadID(m_pReader, idpos, len);
+
+  if (id != libwebm::kMkvCues)
+    return E_FILE_FORMAT_INVALID;
+
+  pos += len;  // consume ID
+  assert((segment_stop < 0) || (pos <= segment_stop));
+
+  // Read Size
+
+  if ((pos + 1) > avail) {
+    len = 1;
+    return E_BUFFER_NOT_FULL;
+  }
+
+  result = GetUIntLength(m_pReader, pos, len);
+
+  if (result < 0)  // error
+    return static_cast<long>(result);
+
+  if (result > 0)  // underflow (weird)
+  {
+    len = 1;
+    return E_BUFFER_NOT_FULL;
+  }
+
+  if ((segment_stop >= 0) && ((pos + len) > segment_stop))
+    return E_FILE_FORMAT_INVALID;
+
+  if ((pos + len) > avail)
+    return E_BUFFER_NOT_FULL;
+
+  const long long size = ReadUInt(m_pReader, pos, len);
+
+  if (size < 0)  // error
+    return static_cast<long>(size);
+
+  if (size == 0)  // weird, although technically not illegal
+    return 1;  // done
+
+  pos += len;  // consume length of size of element
+  assert((segment_stop < 0) || (pos <= segment_stop));
+
+  // Pos now points to start of payload
+
+  const long long element_stop = pos + size;
+
+  if ((segment_stop >= 0) && (element_stop > segment_stop))
+    return E_FILE_FORMAT_INVALID;
+
+  if ((total >= 0) && (element_stop > total))
+    return 1;  // don't bother parsing anymore
+
+  len = static_cast<long>(size);
+
+  if (element_stop > avail)
+    return E_BUFFER_NOT_FULL;
+
+  const long long element_size = element_stop - element_start;
+
+  m_pCues = new Cues(this, pos, size, element_start, element_size);
+
+  return 0;  // success
+}
+
+bool SeekHead::ParseEntry(IMkvReader* pReader, long long start, long long size_,
+                          Entry* pEntry) {
+  if (size_ <= 0)
+    return false;
+
+  long long pos = start;
+  const long long stop = start + size_;
+
+  long len;
+
+  // parse the container for the level-1 element ID
+
+  const long long seekIdId = ReadID(pReader, pos, len);
+  if (seekIdId < 0)
+    return false;
+
+  if (seekIdId != libwebm::kMkvSeekID)
+    return false;
+
+  if ((pos + len) > stop)
+    return false;
+
+  pos += len;  // consume SeekID id
+
+  const long long seekIdSize = ReadUInt(pReader, pos, len);
+
+  if (seekIdSize <= 0)
+    return false;
+
+  if ((pos + len) > stop)
+    return false;
+
+  pos += len;  // consume size of field
+
+  if ((pos + seekIdSize) > stop)
+    return false;
+
+  // Note that the SeekId payload really is serialized
+  // as a "Matroska integer", not as a plain binary value.
+  // In fact, Matroska requires that ID values in the
+  // stream exactly match the binary representation as listed
+  // in the Matroska specification.
+  //
+  // This parser is more liberal, and permits IDs to have
+  // any width.  (This could make the representation in the stream
+  // different from what's in the spec, but it doesn't matter here,
+  // since we always normalize "Matroska integer" values.)
+
+  pEntry->id = ReadUInt(pReader, pos, len);  // payload
+
+  if (pEntry->id <= 0)
+    return false;
+
+  if (len != seekIdSize)
+    return false;
+
+  pos += seekIdSize;  // consume SeekID payload
+
+  const long long seekPosId = ReadID(pReader, pos, len);
+
+  if (seekPosId != libwebm::kMkvSeekPosition)
+    return false;
+
+  if ((pos + len) > stop)
+    return false;
+
+  pos += len;  // consume id
+
+  const long long seekPosSize = ReadUInt(pReader, pos, len);
+
+  if (seekPosSize <= 0)
+    return false;
+
+  if ((pos + len) > stop)
+    return false;
+
+  pos += len;  // consume size
+
+  if ((pos + seekPosSize) > stop)
+    return false;
+
+  pEntry->pos = UnserializeUInt(pReader, pos, seekPosSize);
+
+  if (pEntry->pos < 0)
+    return false;
+
+  pos += seekPosSize;  // consume payload
+
+  if (pos != stop)
+    return false;
+
+  return true;
+}
+
+Cues::Cues(Segment* pSegment, long long start_, long long size_,
+           long long element_start, long long element_size)
+    : m_pSegment(pSegment),
+      m_start(start_),
+      m_size(size_),
+      m_element_start(element_start),
+      m_element_size(element_size),
+      m_cue_points(NULL),
+      m_count(0),
+      m_preload_count(0),
+      m_pos(start_) {}
+
+Cues::~Cues() {
+  const long n = m_count + m_preload_count;
+
+  CuePoint** p = m_cue_points;
+  CuePoint** const q = p + n;
+
+  while (p != q) {
+    CuePoint* const pCP = *p++;
+    assert(pCP);
+
+    delete pCP;
+  }
+
+  delete[] m_cue_points;
+}
+
+long Cues::GetCount() const {
+  if (m_cue_points == NULL)
+    return -1;
+
+  return m_count;  // TODO: really ignore preload count?
+}
+
+bool Cues::DoneParsing() const {
+  const long long stop = m_start + m_size;
+  return (m_pos >= stop);
+}
+
+bool Cues::Init() const {
+  if (m_cue_points)
+    return true;
+
+  if (m_count != 0 || m_preload_count != 0)
+    return false;
+
+  IMkvReader* const pReader = m_pSegment->m_pReader;
+
+  const long long stop = m_start + m_size;
+  long long pos = m_start;
+
+  long cue_points_size = 0;
+
+  while (pos < stop) {
+    const long long idpos = pos;
+
+    long len;
+
+    const long long id = ReadID(pReader, pos, len);
+    if (id < 0 || (pos + len) > stop) {
+      return false;
+    }
+
+    pos += len;  // consume ID
+
+    const long long size = ReadUInt(pReader, pos, len);
+    if (size < 0 || (pos + len > stop)) {
+      return false;
+    }
+
+    pos += len;  // consume Size field
+    if (pos + size > stop) {
+      return false;
+    }
+
+    if (id == libwebm::kMkvCuePoint) {
+      if (!PreloadCuePoint(cue_points_size, idpos))
+        return false;
+    }
+
+    pos += size;  // skip payload
+  }
+  return true;
+}
+
+bool Cues::PreloadCuePoint(long& cue_points_size, long long pos) const {
+  if (m_count != 0)
+    return false;
+
+  if (m_preload_count >= cue_points_size) {
+    const long n = (cue_points_size <= 0) ? 2048 : 2 * cue_points_size;
+
+    CuePoint** const qq = new CuePoint*[n];
+
+    CuePoint** q = qq;  // beginning of target
+
+    CuePoint** p = m_cue_points;  // beginning of source
+    CuePoint** const pp = p + m_preload_count;  // end of source
+
+    while (p != pp)
+      *q++ = *p++;
+
+    delete[] m_cue_points;
+
+    m_cue_points = qq;
+    cue_points_size = n;
+  }
+
+  CuePoint* const pCP = new CuePoint(m_preload_count, pos);
+
+  m_cue_points[m_preload_count++] = pCP;
+  return true;
+}
+
+bool Cues::LoadCuePoint() const {
+  const long long stop = m_start + m_size;
+
+  if (m_pos >= stop)
+    return false;  // nothing else to do
+
+  if (!Init()) {
+    m_pos = stop;
+    return false;
+  }
+
+  IMkvReader* const pReader = m_pSegment->m_pReader;
+
+  while (m_pos < stop) {
+    const long long idpos = m_pos;
+
+    long len;
+
+    const long long id = ReadID(pReader, m_pos, len);
+    if (id < 0 || (m_pos + len) > stop)
+      return false;
+
+    m_pos += len;  // consume ID
+
+    const long long size = ReadUInt(pReader, m_pos, len);
+    if (size < 0 || (m_pos + len) > stop)
+      return false;
+
+    m_pos += len;  // consume Size field
+    if ((m_pos + size) > stop)
+      return false;
+
+    if (id != libwebm::kMkvCuePoint) {
+      m_pos += size;  // consume payload
+      if (m_pos > stop)
+        return false;
+
+      continue;
+    }
+
+    if (m_preload_count < 1)
+      return false;
+
+    CuePoint* const pCP = m_cue_points[m_count];
+    if (!pCP || (pCP->GetTimeCode() < 0 && (-pCP->GetTimeCode() != idpos)))
+      return false;
+
+    if (!pCP->Load(pReader)) {
+      m_pos = stop;
+      return false;
+    }
+    ++m_count;
+    --m_preload_count;
+
+    m_pos += size;  // consume payload
+    if (m_pos > stop)
+      return false;
+
+    return true;  // yes, we loaded a cue point
+  }
+
+  return false;  // no, we did not load a cue point
+}
+
+bool Cues::Find(long long time_ns, const Track* pTrack, const CuePoint*& pCP,
+                const CuePoint::TrackPosition*& pTP) const {
+  if (time_ns < 0 || pTrack == NULL || m_cue_points == NULL || m_count == 0)
+    return false;
+
+  CuePoint** const ii = m_cue_points;
+  CuePoint** i = ii;
+
+  CuePoint** const jj = ii + m_count;
+  CuePoint** j = jj;
+
+  pCP = *i;
+  if (pCP == NULL)
+    return false;
+
+  if (time_ns <= pCP->GetTime(m_pSegment)) {
+    pTP = pCP->Find(pTrack);
+    return (pTP != NULL);
+  }
+
+  while (i < j) {
+    // INVARIANT:
+    //[ii, i) <= time_ns
+    //[i, j)  ?
+    //[j, jj) > time_ns
+
+    CuePoint** const k = i + (j - i) / 2;
+    if (k >= jj)
+      return false;
+
+    CuePoint* const pCP = *k;
+    if (pCP == NULL)
+      return false;
+
+    const long long t = pCP->GetTime(m_pSegment);
+
+    if (t <= time_ns)
+      i = k + 1;
+    else
+      j = k;
+
+    if (i > j)
+      return false;
+  }
+
+  if (i != j || i > jj || i <= ii)
+    return false;
+
+  pCP = *--i;
+
+  if (pCP == NULL || pCP->GetTime(m_pSegment) > time_ns)
+    return false;
+
+  // TODO: here and elsewhere, it's probably not correct to search
+  // for the cue point with this time, and then search for a matching
+  // track.  In principle, the matching track could be on some earlier
+  // cue point, and with our current algorithm, we'd miss it.  To make
+  // this bullet-proof, we'd need to create a secondary structure,
+  // with a list of cue points that apply to a track, and then search
+  // that track-based structure for a matching cue point.
+
+  pTP = pCP->Find(pTrack);
+  return (pTP != NULL);
+}
+
+const CuePoint* Cues::GetFirst() const {
+  if (m_cue_points == NULL || m_count == 0)
+    return NULL;
+
+  CuePoint* const* const pp = m_cue_points;
+  if (pp == NULL)
+    return NULL;
+
+  CuePoint* const pCP = pp[0];
+  if (pCP == NULL || pCP->GetTimeCode() < 0)
+    return NULL;
+
+  return pCP;
+}
+
+const CuePoint* Cues::GetLast() const {
+  if (m_cue_points == NULL || m_count <= 0)
+    return NULL;
+
+  const long index = m_count - 1;
+
+  CuePoint* const* const pp = m_cue_points;
+  if (pp == NULL)
+    return NULL;
+
+  CuePoint* const pCP = pp[index];
+  if (pCP == NULL || pCP->GetTimeCode() < 0)
+    return NULL;
+
+  return pCP;
+}
+
+const CuePoint* Cues::GetNext(const CuePoint* pCurr) const {
+  if (pCurr == NULL || pCurr->GetTimeCode() < 0 || m_cue_points == NULL ||
+      m_count < 1) {
+    return NULL;
+  }
+
+  long index = pCurr->m_index;
+  if (index >= m_count)
+    return NULL;
+
+  CuePoint* const* const pp = m_cue_points;
+  if (pp == NULL || pp[index] != pCurr)
+    return NULL;
+
+  ++index;
+
+  if (index >= m_count)
+    return NULL;
+
+  CuePoint* const pNext = pp[index];
+
+  if (pNext == NULL || pNext->GetTimeCode() < 0)
+    return NULL;
+
+  return pNext;
+}
+
+const BlockEntry* Cues::GetBlock(const CuePoint* pCP,
+                                 const CuePoint::TrackPosition* pTP) const {
+  if (pCP == NULL || pTP == NULL)
+    return NULL;
+
+  return m_pSegment->GetBlock(*pCP, *pTP);
+}
+
+const BlockEntry* Segment::GetBlock(const CuePoint& cp,
+                                    const CuePoint::TrackPosition& tp) {
+  Cluster** const ii = m_clusters;
+  Cluster** i = ii;
+
+  const long count = m_clusterCount + m_clusterPreloadCount;
+
+  Cluster** const jj = ii + count;
+  Cluster** j = jj;
+
+  while (i < j) {
+    // INVARIANT:
+    //[ii, i) < pTP->m_pos
+    //[i, j) ?
+    //[j, jj)  > pTP->m_pos
+
+    Cluster** const k = i + (j - i) / 2;
+    assert(k < jj);
+
+    Cluster* const pCluster = *k;
+    assert(pCluster);
+
+    // const long long pos_ = pCluster->m_pos;
+    // assert(pos_);
+    // const long long pos = pos_ * ((pos_ < 0) ? -1 : 1);
+
+    const long long pos = pCluster->GetPosition();
+    assert(pos >= 0);
+
+    if (pos < tp.m_pos)
+      i = k + 1;
+    else if (pos > tp.m_pos)
+      j = k;
+    else
+      return pCluster->GetEntry(cp, tp);
+  }
+
+  assert(i == j);
+  // assert(Cluster::HasBlockEntries(this, tp.m_pos));
+
+  Cluster* const pCluster = Cluster::Create(this, -1, tp.m_pos);  //, -1);
+  if (pCluster == NULL)
+    return NULL;
+
+  const ptrdiff_t idx = i - m_clusters;
+
+  if (!PreloadCluster(pCluster, idx)) {
+    delete pCluster;
+    return NULL;
+  }
+  assert(m_clusters);
+  assert(m_clusterPreloadCount > 0);
+  assert(m_clusters[idx] == pCluster);
+
+  return pCluster->GetEntry(cp, tp);
+}
+
+const Cluster* Segment::FindOrPreloadCluster(long long requested_pos) {
+  if (requested_pos < 0)
+    return 0;
+
+  Cluster** const ii = m_clusters;
+  Cluster** i = ii;
+
+  const long count = m_clusterCount + m_clusterPreloadCount;
+
+  Cluster** const jj = ii + count;
+  Cluster** j = jj;
+
+  while (i < j) {
+    // INVARIANT:
+    //[ii, i) < pTP->m_pos
+    //[i, j) ?
+    //[j, jj)  > pTP->m_pos
+
+    Cluster** const k = i + (j - i) / 2;
+    assert(k < jj);
+
+    Cluster* const pCluster = *k;
+    assert(pCluster);
+
+    // const long long pos_ = pCluster->m_pos;
+    // assert(pos_);
+    // const long long pos = pos_ * ((pos_ < 0) ? -1 : 1);
+
+    const long long pos = pCluster->GetPosition();
+    assert(pos >= 0);
+
+    if (pos < requested_pos)
+      i = k + 1;
+    else if (pos > requested_pos)
+      j = k;
+    else
+      return pCluster;
+  }
+
+  assert(i == j);
+  // assert(Cluster::HasBlockEntries(this, tp.m_pos));
+
+  Cluster* const pCluster = Cluster::Create(this, -1, requested_pos);
+  if (pCluster == NULL)
+    return NULL;
+
+  const ptrdiff_t idx = i - m_clusters;
+
+  if (!PreloadCluster(pCluster, idx)) {
+    delete pCluster;
+    return NULL;
+  }
+  assert(m_clusters);
+  assert(m_clusterPreloadCount > 0);
+  assert(m_clusters[idx] == pCluster);
+
+  return pCluster;
+}
+
+CuePoint::CuePoint(long idx, long long pos)
+    : m_element_start(0),
+      m_element_size(0),
+      m_index(idx),
+      m_timecode(-1 * pos),
+      m_track_positions(NULL),
+      m_track_positions_count(0) {
+  assert(pos > 0);
+}
+
+CuePoint::~CuePoint() { delete[] m_track_positions; }
+
+bool CuePoint::Load(IMkvReader* pReader) {
+  // odbgstream os;
+  // os << "CuePoint::Load(begin): timecode=" << m_timecode << endl;
+
+  if (m_timecode >= 0)  // already loaded
+    return true;
+
+  assert(m_track_positions == NULL);
+  assert(m_track_positions_count == 0);
+
+  long long pos_ = -m_timecode;
+  const long long element_start = pos_;
+
+  long long stop;
+
+  {
+    long len;
+
+    const long long id = ReadID(pReader, pos_, len);
+    if (id != libwebm::kMkvCuePoint)
+      return false;
+
+    pos_ += len;  // consume ID
+
+    const long long size = ReadUInt(pReader, pos_, len);
+    assert(size >= 0);
+
+    pos_ += len;  // consume Size field
+    // pos_ now points to start of payload
+
+    stop = pos_ + size;
+  }
+
+  const long long element_size = stop - element_start;
+
+  long long pos = pos_;
+
+  // First count number of track positions
+
+  while (pos < stop) {
+    long len;
+
+    const long long id = ReadID(pReader, pos, len);
+    if ((id < 0) || (pos + len > stop)) {
+      return false;
+    }
+
+    pos += len;  // consume ID
+
+    const long long size = ReadUInt(pReader, pos, len);
+    if ((size < 0) || (pos + len > stop)) {
+      return false;
+    }
+
+    pos += len;  // consume Size field
+    if ((pos + size) > stop) {
+      return false;
+    }
+
+    if (id == libwebm::kMkvCueTime)
+      m_timecode = UnserializeUInt(pReader, pos, size);
+
+    else if (id == libwebm::kMkvCueTrackPositions)
+      ++m_track_positions_count;
+
+    pos += size;  // consume payload
+  }
+
+  if (m_timecode < 0 || m_track_positions_count <= 0) {
+    return false;
+  }
+
+  // os << "CuePoint::Load(cont'd): idpos=" << idpos
+  //   << " timecode=" << m_timecode
+  //   << endl;
+
+  m_track_positions = new TrackPosition[m_track_positions_count];
+
+  // Now parse track positions
+
+  TrackPosition* p = m_track_positions;
+  pos = pos_;
+
+  while (pos < stop) {
+    long len;
+
+    const long long id = ReadID(pReader, pos, len);
+    if (id < 0 || (pos + len) > stop)
+      return false;
+
+    pos += len;  // consume ID
+
+    const long long size = ReadUInt(pReader, pos, len);
+    assert(size >= 0);
+    assert((pos + len) <= stop);
+
+    pos += len;  // consume Size field
+    assert((pos + size) <= stop);
+
+    if (id == libwebm::kMkvCueTrackPositions) {
+      TrackPosition& tp = *p++;
+      if (!tp.Parse(pReader, pos, size)) {
+        return false;
+      }
+    }
+
+    pos += size;  // consume payload
+    if (pos > stop)
+      return false;
+  }
+
+  assert(size_t(p - m_track_positions) == m_track_positions_count);
+
+  m_element_start = element_start;
+  m_element_size = element_size;
+
+  return true;
+}
+
+bool CuePoint::TrackPosition::Parse(IMkvReader* pReader, long long start_,
+                                    long long size_) {
+  const long long stop = start_ + size_;
+  long long pos = start_;
+
+  m_track = -1;
+  m_pos = -1;
+  m_block = 1;  // default
+
+  while (pos < stop) {
+    long len;
+
+    const long long id = ReadID(pReader, pos, len);
+    if ((id < 0) || ((pos + len) > stop)) {
+      return false;
+    }
+
+    pos += len;  // consume ID
+
+    const long long size = ReadUInt(pReader, pos, len);
+    if ((size < 0) || ((pos + len) > stop)) {
+      return false;
+    }
+
+    pos += len;  // consume Size field
+    if ((pos + size) > stop) {
+      return false;
+    }
+
+    if (id == libwebm::kMkvCueTrack)
+      m_track = UnserializeUInt(pReader, pos, size);
+    else if (id == libwebm::kMkvCueClusterPosition)
+      m_pos = UnserializeUInt(pReader, pos, size);
+    else if (id == libwebm::kMkvCueBlockNumber)
+      m_block = UnserializeUInt(pReader, pos, size);
+
+    pos += size;  // consume payload
+  }
+
+  if ((m_pos < 0) || (m_track <= 0)) {
+    return false;
+  }
+
+  return true;
+}
+
+const CuePoint::TrackPosition* CuePoint::Find(const Track* pTrack) const {
+  assert(pTrack);
+
+  const long long n = pTrack->GetNumber();
+
+  const TrackPosition* i = m_track_positions;
+  const TrackPosition* const j = i + m_track_positions_count;
+
+  while (i != j) {
+    const TrackPosition& p = *i++;
+
+    if (p.m_track == n)
+      return &p;
+  }
+
+  return NULL;  // no matching track number found
+}
+
+long long CuePoint::GetTimeCode() const { return m_timecode; }
+
+long long CuePoint::GetTime(const Segment* pSegment) const {
+  assert(pSegment);
+  assert(m_timecode >= 0);
+
+  const SegmentInfo* const pInfo = pSegment->GetInfo();
+  assert(pInfo);
+
+  const long long scale = pInfo->GetTimeCodeScale();
+  assert(scale >= 1);
+
+  const long long time = scale * m_timecode;
+
+  return time;
+}
+
+bool Segment::DoneParsing() const {
+  if (m_size < 0) {
+    long long total, avail;
+
+    const int status = m_pReader->Length(&total, &avail);
+
+    if (status < 0)  // error
+      return true;  // must assume done
+
+    if (total < 0)
+      return false;  // assume live stream
+
+    return (m_pos >= total);
+  }
+
+  const long long stop = m_start + m_size;
+
+  return (m_pos >= stop);
+}
+
+const Cluster* Segment::GetFirst() const {
+  if ((m_clusters == NULL) || (m_clusterCount <= 0))
+    return &m_eos;
+
+  Cluster* const pCluster = m_clusters[0];
+  assert(pCluster);
+
+  return pCluster;
+}
+
+const Cluster* Segment::GetLast() const {
+  if ((m_clusters == NULL) || (m_clusterCount <= 0))
+    return &m_eos;
+
+  const long idx = m_clusterCount - 1;
+
+  Cluster* const pCluster = m_clusters[idx];
+  assert(pCluster);
+
+  return pCluster;
+}
+
+unsigned long Segment::GetCount() const { return m_clusterCount; }
+
+const Cluster* Segment::GetNext(const Cluster* pCurr) {
+  assert(pCurr);
+  assert(pCurr != &m_eos);
+  assert(m_clusters);
+
+  long idx = pCurr->m_index;
+
+  if (idx >= 0) {
+    assert(m_clusterCount > 0);
+    assert(idx < m_clusterCount);
+    assert(pCurr == m_clusters[idx]);
+
+    ++idx;
+
+    if (idx >= m_clusterCount)
+      return &m_eos;  // caller will LoadCluster as desired
+
+    Cluster* const pNext = m_clusters[idx];
+    assert(pNext);
+    assert(pNext->m_index >= 0);
+    assert(pNext->m_index == idx);
+
+    return pNext;
+  }
+
+  assert(m_clusterPreloadCount > 0);
+
+  long long pos = pCurr->m_element_start;
+
+  assert(m_size >= 0);  // TODO
+  const long long stop = m_start + m_size;  // end of segment
+
+  {
+    long len;
+
+    long long result = GetUIntLength(m_pReader, pos, len);
+    assert(result == 0);
+    assert((pos + len) <= stop);  // TODO
+    if (result != 0)
+      return NULL;
+
+    const long long id = ReadID(m_pReader, pos, len);
+    if (id != libwebm::kMkvCluster)
+      return NULL;
+
+    pos += len;  // consume ID
+
+    // Read Size
+    result = GetUIntLength(m_pReader, pos, len);
+    assert(result == 0);  // TODO
+    assert((pos + len) <= stop);  // TODO
+
+    const long long size = ReadUInt(m_pReader, pos, len);
+    assert(size > 0);  // TODO
+    // assert((pCurr->m_size <= 0) || (pCurr->m_size == size));
+
+    pos += len;  // consume length of size of element
+    assert((pos + size) <= stop);  // TODO
+
+    // Pos now points to start of payload
+
+    pos += size;  // consume payload
+  }
+
+  long long off_next = 0;
+
+  while (pos < stop) {
+    long len;
+
+    long long result = GetUIntLength(m_pReader, pos, len);
+    assert(result == 0);
+    assert((pos + len) <= stop);  // TODO
+    if (result != 0)
+      return NULL;
+
+    const long long idpos = pos;  // pos of next (potential) cluster
+
+    const long long id = ReadID(m_pReader, idpos, len);
+    if (id < 0)
+      return NULL;
+
+    pos += len;  // consume ID
+
+    // Read Size
+    result = GetUIntLength(m_pReader, pos, len);
+    assert(result == 0);  // TODO
+    assert((pos + len) <= stop);  // TODO
+
+    const long long size = ReadUInt(m_pReader, pos, len);
+    assert(size >= 0);  // TODO
+
+    pos += len;  // consume length of size of element
+    assert((pos + size) <= stop);  // TODO
+
+    // Pos now points to start of payload
+
+    if (size == 0)  // weird
+      continue;
+
+    if (id == libwebm::kMkvCluster) {
+      const long long off_next_ = idpos - m_start;
+
+      long long pos_;
+      long len_;
+
+      const long status = Cluster::HasBlockEntries(this, off_next_, pos_, len_);
+
+      assert(status >= 0);
+
+      if (status > 0) {
+        off_next = off_next_;
+        break;
+      }
+    }
+
+    pos += size;  // consume payload
+  }
+
+  if (off_next <= 0)
+    return 0;
+
+  Cluster** const ii = m_clusters + m_clusterCount;
+  Cluster** i = ii;
+
+  Cluster** const jj = ii + m_clusterPreloadCount;
+  Cluster** j = jj;
+
+  while (i < j) {
+    // INVARIANT:
+    //[0, i) < pos_next
+    //[i, j) ?
+    //[j, jj)  > pos_next
+
+    Cluster** const k = i + (j - i) / 2;
+    assert(k < jj);
+
+    Cluster* const pNext = *k;
+    assert(pNext);
+    assert(pNext->m_index < 0);
+
+    // const long long pos_ = pNext->m_pos;
+    // assert(pos_);
+    // pos = pos_ * ((pos_ < 0) ? -1 : 1);
+
+    pos = pNext->GetPosition();
+
+    if (pos < off_next)
+      i = k + 1;
+    else if (pos > off_next)
+      j = k;
+    else
+      return pNext;
+  }
+
+  assert(i == j);
+
+  Cluster* const pNext = Cluster::Create(this, -1, off_next);
+  if (pNext == NULL)
+    return NULL;
+
+  const ptrdiff_t idx_next = i - m_clusters;  // insertion position
+
+  if (!PreloadCluster(pNext, idx_next)) {
+    delete pNext;
+    return NULL;
+  }
+  assert(m_clusters);
+  assert(idx_next < m_clusterSize);
+  assert(m_clusters[idx_next] == pNext);
+
+  return pNext;
+}
+
+long Segment::ParseNext(const Cluster* pCurr, const Cluster*& pResult,
+                        long long& pos, long& len) {
+  assert(pCurr);
+  assert(!pCurr->EOS());
+  assert(m_clusters);
+
+  pResult = 0;
+
+  if (pCurr->m_index >= 0) {  // loaded (not merely preloaded)
+    assert(m_clusters[pCurr->m_index] == pCurr);
+
+    const long next_idx = pCurr->m_index + 1;
+
+    if (next_idx < m_clusterCount) {
+      pResult = m_clusters[next_idx];
+      return 0;  // success
+    }
+
+    // curr cluster is last among loaded
+
+    const long result = LoadCluster(pos, len);
+
+    if (result < 0)  // error or underflow
+      return result;
+
+    if (result > 0)  // no more clusters
+    {
+      // pResult = &m_eos;
+      return 1;
+    }
+
+    pResult = GetLast();
+    return 0;  // success
+  }
+
+  assert(m_pos > 0);
+
+  long long total, avail;
+
+  long status = m_pReader->Length(&total, &avail);
+
+  if (status < 0)  // error
+    return status;
+
+  assert((total < 0) || (avail <= total));
+
+  const long long segment_stop = (m_size < 0) ? -1 : m_start + m_size;
+
+  // interrogate curr cluster
+
+  pos = pCurr->m_element_start;
+
+  if (pCurr->m_element_size >= 0)
+    pos += pCurr->m_element_size;
+  else {
+    if ((pos + 1) > avail) {
+      len = 1;
+      return E_BUFFER_NOT_FULL;
+    }
+
+    long long result = GetUIntLength(m_pReader, pos, len);
+
+    if (result < 0)  // error
+      return static_cast<long>(result);
+
+    if (result > 0)  // weird
+      return E_BUFFER_NOT_FULL;
+
+    if ((segment_stop >= 0) && ((pos + len) > segment_stop))
+      return E_FILE_FORMAT_INVALID;
+
+    if ((pos + len) > avail)
+      return E_BUFFER_NOT_FULL;
+
+    const long long id = ReadUInt(m_pReader, pos, len);
+
+    if (id != libwebm::kMkvCluster)
+      return -1;
+
+    pos += len;  // consume ID
+
+    // Read Size
+
+    if ((pos + 1) > avail) {
+      len = 1;
+      return E_BUFFER_NOT_FULL;
+    }
+
+    result = GetUIntLength(m_pReader, pos, len);
+
+    if (result < 0)  // error
+      return static_cast<long>(result);
+
+    if (result > 0)  // weird
+      return E_BUFFER_NOT_FULL;
+
+    if ((segment_stop >= 0) && ((pos + len) > segment_stop))
+      return E_FILE_FORMAT_INVALID;
+
+    if ((pos + len) > avail)
+      return E_BUFFER_NOT_FULL;
+
+    const long long size = ReadUInt(m_pReader, pos, len);
+
+    if (size < 0)  // error
+      return static_cast<long>(size);
+
+    pos += len;  // consume size field
+
+    const long long unknown_size = (1LL << (7 * len)) - 1;
+
+    if (size == unknown_size)  // TODO: should never happen
+      return E_FILE_FORMAT_INVALID;  // TODO: resolve this
+
+    // assert((pCurr->m_size <= 0) || (pCurr->m_size == size));
+
+    if ((segment_stop >= 0) && ((pos + size) > segment_stop))
+      return E_FILE_FORMAT_INVALID;
+
+    // Pos now points to start of payload
+
+    pos += size;  // consume payload (that is, the current cluster)
+    if (segment_stop >= 0 && pos > segment_stop)
+      return E_FILE_FORMAT_INVALID;
+
+    // By consuming the payload, we are assuming that the curr
+    // cluster isn't interesting.  That is, we don't bother checking
+    // whether the payload of the curr cluster is less than what
+    // happens to be available (obtained via IMkvReader::Length).
+    // Presumably the caller has already dispensed with the current
+    // cluster, and really does want the next cluster.
+  }
+
+  // pos now points to just beyond the last fully-loaded cluster
+
+  for (;;) {
+    const long status = DoParseNext(pResult, pos, len);
+
+    if (status <= 1)
+      return status;
+  }
+}
+
+long Segment::DoParseNext(const Cluster*& pResult, long long& pos, long& len) {
+  long long total, avail;
+
+  long status = m_pReader->Length(&total, &avail);
+
+  if (status < 0)  // error
+    return status;
+
+  assert((total < 0) || (avail <= total));
+
+  const long long segment_stop = (m_size < 0) ? -1 : m_start + m_size;
+
+  // Parse next cluster.  This is strictly a parsing activity.
+  // Creation of a new cluster object happens later, after the
+  // parsing is done.
+
+  long long off_next = 0;
+  long long cluster_size = -1;
+
+  for (;;) {
+    if ((total >= 0) && (pos >= total))
+      return 1;  // EOF
+
+    if ((segment_stop >= 0) && (pos >= segment_stop))
+      return 1;  // EOF
+
+    if ((pos + 1) > avail) {
+      len = 1;
+      return E_BUFFER_NOT_FULL;
+    }
+
+    long long result = GetUIntLength(m_pReader, pos, len);
+
+    if (result < 0)  // error
+      return static_cast<long>(result);
+
+    if (result > 0)  // weird
+      return E_BUFFER_NOT_FULL;
+
+    if ((segment_stop >= 0) && ((pos + len) > segment_stop))
+      return E_FILE_FORMAT_INVALID;
+
+    if ((pos + len) > avail)
+      return E_BUFFER_NOT_FULL;
+
+    const long long idpos = pos;  // absolute
+    const long long idoff = pos - m_start;  // relative
+
+    const long long id = ReadID(m_pReader, idpos, len);  // absolute
+
+    if (id < 0)  // error
+      return static_cast<long>(id);
+
+    if (id == 0)  // weird
+      return -1;  // generic error
+
+    pos += len;  // consume ID
+
+    // Read Size
+
+    if ((pos + 1) > avail) {
+      len = 1;
+      return E_BUFFER_NOT_FULL;
+    }
+
+    result = GetUIntLength(m_pReader, pos, len);
+
+    if (result < 0)  // error
+      return static_cast<long>(result);
+
+    if (result > 0)  // weird
+      return E_BUFFER_NOT_FULL;
+
+    if ((segment_stop >= 0) && ((pos + len) > segment_stop))
+      return E_FILE_FORMAT_INVALID;
+
+    if ((pos + len) > avail)
+      return E_BUFFER_NOT_FULL;
+
+    const long long size = ReadUInt(m_pReader, pos, len);
+
+    if (size < 0)  // error
+      return static_cast<long>(size);
+
+    pos += len;  // consume length of size of element
+
+    // Pos now points to start of payload
+
+    if (size == 0)  // weird
+      continue;
+
+    const long long unknown_size = (1LL << (7 * len)) - 1;
+
+    if ((segment_stop >= 0) && (size != unknown_size) &&
+        ((pos + size) > segment_stop)) {
+      return E_FILE_FORMAT_INVALID;
+    }
+
+    if (id == libwebm::kMkvCues) {
+      if (size == unknown_size)
+        return E_FILE_FORMAT_INVALID;
+
+      const long long element_stop = pos + size;
+
+      if ((segment_stop >= 0) && (element_stop > segment_stop))
+        return E_FILE_FORMAT_INVALID;
+
+      const long long element_start = idpos;
+      const long long element_size = element_stop - element_start;
+
+      if (m_pCues == NULL) {
+        m_pCues = new Cues(this, pos, size, element_start, element_size);
+      }
+
+      pos += size;  // consume payload
+      if (segment_stop >= 0 && pos > segment_stop)
+        return E_FILE_FORMAT_INVALID;
+
+      continue;
+    }
+
+    if (id != libwebm::kMkvCluster) {  // not a Cluster ID
+      if (size == unknown_size)
+        return E_FILE_FORMAT_INVALID;
+
+      pos += size;  // consume payload
+      if (segment_stop >= 0 && pos > segment_stop)
+        return E_FILE_FORMAT_INVALID;
+
+      continue;
+    }
+
+    // We have a cluster.
+    off_next = idoff;
+
+    if (size != unknown_size)
+      cluster_size = size;
+
+    break;
+  }
+
+  assert(off_next > 0);  // have cluster
+
+  // We have parsed the next cluster.
+  // We have not created a cluster object yet.  What we need
+  // to do now is determine whether it has already be preloaded
+  //(in which case, an object for this cluster has already been
+  // created), and if not, create a new cluster object.
+
+  Cluster** const ii = m_clusters + m_clusterCount;
+  Cluster** i = ii;
+
+  Cluster** const jj = ii + m_clusterPreloadCount;
+  Cluster** j = jj;
+
+  while (i < j) {
+    // INVARIANT:
+    //[0, i) < pos_next
+    //[i, j) ?
+    //[j, jj)  > pos_next
+
+    Cluster** const k = i + (j - i) / 2;
+    assert(k < jj);
+
+    const Cluster* const pNext = *k;
+    assert(pNext);
+    assert(pNext->m_index < 0);
+
+    pos = pNext->GetPosition();
+    assert(pos >= 0);
+
+    if (pos < off_next)
+      i = k + 1;
+    else if (pos > off_next)
+      j = k;
+    else {
+      pResult = pNext;
+      return 0;  // success
+    }
+  }
+
+  assert(i == j);
+
+  long long pos_;
+  long len_;
+
+  status = Cluster::HasBlockEntries(this, off_next, pos_, len_);
+
+  if (status < 0) {  // error or underflow
+    pos = pos_;
+    len = len_;
+
+    return status;
+  }
+
+  if (status > 0) {  // means "found at least one block entry"
+    Cluster* const pNext = Cluster::Create(this,
+                                           -1,  // preloaded
+                                           off_next);
+    if (pNext == NULL)
+      return -1;
+
+    const ptrdiff_t idx_next = i - m_clusters;  // insertion position
+
+    if (!PreloadCluster(pNext, idx_next)) {
+      delete pNext;
+      return -1;
+    }
+    assert(m_clusters);
+    assert(idx_next < m_clusterSize);
+    assert(m_clusters[idx_next] == pNext);
+
+    pResult = pNext;
+    return 0;  // success
+  }
+
+  // status == 0 means "no block entries found"
+
+  if (cluster_size < 0) {  // unknown size
+    const long long payload_pos = pos;  // absolute pos of cluster payload
+
+    for (;;) {  // determine cluster size
+      if ((total >= 0) && (pos >= total))
+        break;
+
+      if ((segment_stop >= 0) && (pos >= segment_stop))
+        break;  // no more clusters
+
+      // Read ID
+
+      if ((pos + 1) > avail) {
+        len = 1;
+        return E_BUFFER_NOT_FULL;
+      }
+
+      long long result = GetUIntLength(m_pReader, pos, len);
+
+      if (result < 0)  // error
+        return static_cast<long>(result);
+
+      if (result > 0)  // weird
+        return E_BUFFER_NOT_FULL;
+
+      if ((segment_stop >= 0) && ((pos + len) > segment_stop))
+        return E_FILE_FORMAT_INVALID;
+
+      if ((pos + len) > avail)
+        return E_BUFFER_NOT_FULL;
+
+      const long long idpos = pos;
+      const long long id = ReadID(m_pReader, idpos, len);
+
+      if (id < 0)  // error (or underflow)
+        return static_cast<long>(id);
+
+      // This is the distinguished set of ID's we use to determine
+      // that we have exhausted the sub-element's inside the cluster
+      // whose ID we parsed earlier.
+
+      if (id == libwebm::kMkvCluster || id == libwebm::kMkvCues)
+        break;
+
+      pos += len;  // consume ID (of sub-element)
+
+      // Read Size
+
+      if ((pos + 1) > avail) {
+        len = 1;
+        return E_BUFFER_NOT_FULL;
+      }
+
+      result = GetUIntLength(m_pReader, pos, len);
+
+      if (result < 0)  // error
+        return static_cast<long>(result);
+
+      if (result > 0)  // weird
+        return E_BUFFER_NOT_FULL;
+
+      if ((segment_stop >= 0) && ((pos + len) > segment_stop))
+        return E_FILE_FORMAT_INVALID;
+
+      if ((pos + len) > avail)
+        return E_BUFFER_NOT_FULL;
+
+      const long long size = ReadUInt(m_pReader, pos, len);
+
+      if (size < 0)  // error
+        return static_cast<long>(size);
+
+      pos += len;  // consume size field of element
+
+      // pos now points to start of sub-element's payload
+
+      if (size == 0)  // weird
+        continue;
+
+      const long long unknown_size = (1LL << (7 * len)) - 1;
+
+      if (size == unknown_size)
+        return E_FILE_FORMAT_INVALID;  // not allowed for sub-elements
+
+      if ((segment_stop >= 0) && ((pos + size) > segment_stop))  // weird
+        return E_FILE_FORMAT_INVALID;
+
+      pos += size;  // consume payload of sub-element
+      if (segment_stop >= 0 && pos > segment_stop)
+        return E_FILE_FORMAT_INVALID;
+    }  // determine cluster size
+
+    cluster_size = pos - payload_pos;
+    assert(cluster_size >= 0);  // TODO: handle cluster_size = 0
+
+    pos = payload_pos;  // reset and re-parse original cluster
+  }
+
+  pos += cluster_size;  // consume payload
+  if (segment_stop >= 0 && pos > segment_stop)
+    return E_FILE_FORMAT_INVALID;
+
+  return 2;  // try to find a cluster that follows next
+}
+
+const Cluster* Segment::FindCluster(long long time_ns) const {
+  if ((m_clusters == NULL) || (m_clusterCount <= 0))
+    return &m_eos;
+
+  {
+    Cluster* const pCluster = m_clusters[0];
+    assert(pCluster);
+    assert(pCluster->m_index == 0);
+
+    if (time_ns <= pCluster->GetTime())
+      return pCluster;
+  }
+
+  // Binary search of cluster array
+
+  long i = 0;
+  long j = m_clusterCount;
+
+  while (i < j) {
+    // INVARIANT:
+    //[0, i) <= time_ns
+    //[i, j) ?
+    //[j, m_clusterCount)  > time_ns
+
+    const long k = i + (j - i) / 2;
+    assert(k < m_clusterCount);
+
+    Cluster* const pCluster = m_clusters[k];
+    assert(pCluster);
+    assert(pCluster->m_index == k);
+
+    const long long t = pCluster->GetTime();
+
+    if (t <= time_ns)
+      i = k + 1;
+    else
+      j = k;
+
+    assert(i <= j);
+  }
+
+  assert(i == j);
+  assert(i > 0);
+  assert(i <= m_clusterCount);
+
+  const long k = i - 1;
+
+  Cluster* const pCluster = m_clusters[k];
+  assert(pCluster);
+  assert(pCluster->m_index == k);
+  assert(pCluster->GetTime() <= time_ns);
+
+  return pCluster;
+}
+
+const Tracks* Segment::GetTracks() const { return m_pTracks; }
+const SegmentInfo* Segment::GetInfo() const { return m_pInfo; }
+const Cues* Segment::GetCues() const { return m_pCues; }
+const Chapters* Segment::GetChapters() const { return m_pChapters; }
+const Tags* Segment::GetTags() const { return m_pTags; }
+const SeekHead* Segment::GetSeekHead() const { return m_pSeekHead; }
+
+long long Segment::GetDuration() const {
+  assert(m_pInfo);
+  return m_pInfo->GetDuration();
+}
+
+Chapters::Chapters(Segment* pSegment, long long payload_start,
+                   long long payload_size, long long element_start,
+                   long long element_size)
+    : m_pSegment(pSegment),
+      m_start(payload_start),
+      m_size(payload_size),
+      m_element_start(element_start),
+      m_element_size(element_size),
+      m_editions(NULL),
+      m_editions_size(0),
+      m_editions_count(0) {}
+
+Chapters::~Chapters() {
+  while (m_editions_count > 0) {
+    Edition& e = m_editions[--m_editions_count];
+    e.Clear();
+  }
+  delete[] m_editions;
+}
+
+long Chapters::Parse() {
+  IMkvReader* const pReader = m_pSegment->m_pReader;
+
+  long long pos = m_start;  // payload start
+  const long long stop = pos + m_size;  // payload stop
+
+  while (pos < stop) {
+    long long id, size;
+
+    long status = ParseElementHeader(pReader, pos, stop, id, size);
+
+    if (status < 0)  // error
+      return status;
+
+    if (size == 0)  // weird
+      continue;
+
+    if (id == libwebm::kMkvEditionEntry) {
+      status = ParseEdition(pos, size);
+
+      if (status < 0)  // error
+        return status;
+    }
+
+    pos += size;
+    if (pos > stop)
+      return E_FILE_FORMAT_INVALID;
+  }
+
+  if (pos != stop)
+    return E_FILE_FORMAT_INVALID;
+  return 0;
+}
+
+int Chapters::GetEditionCount() const { return m_editions_count; }
+
+const Chapters::Edition* Chapters::GetEdition(int idx) const {
+  if (idx < 0)
+    return NULL;
+
+  if (idx >= m_editions_count)
+    return NULL;
+
+  return m_editions + idx;
+}
+
+bool Chapters::ExpandEditionsArray() {
+  if (m_editions_size > m_editions_count)
+    return true;  // nothing else to do
+
+  const int size = (m_editions_size == 0) ? 1 : 2 * m_editions_size;
+
+  Edition* const editions = new Edition[size];
+
+  for (int idx = 0; idx < m_editions_count; ++idx) {
+    m_editions[idx].ShallowCopy(editions[idx]);
+  }
+
+  delete[] m_editions;
+  m_editions = editions;
+
+  m_editions_size = size;
+  return true;
+}
+
+long Chapters::ParseEdition(long long pos, long long size) {
+  if (!ExpandEditionsArray())
+    return -1;
+
+  Edition& e = m_editions[m_editions_count++];
+  e.Init();
+
+  return e.Parse(m_pSegment->m_pReader, pos, size);
+}
+
+Chapters::Edition::Edition() {}
+
+Chapters::Edition::~Edition() {}
+
+int Chapters::Edition::GetAtomCount() const { return m_atoms_count; }
+
+const Chapters::Atom* Chapters::Edition::GetAtom(int index) const {
+  if (index < 0)
+    return NULL;
+
+  if (index >= m_atoms_count)
+    return NULL;
+
+  return m_atoms + index;
+}
+
+void Chapters::Edition::Init() {
+  m_atoms = NULL;
+  m_atoms_size = 0;
+  m_atoms_count = 0;
+}
+
+void Chapters::Edition::ShallowCopy(Edition& rhs) const {
+  rhs.m_atoms = m_atoms;
+  rhs.m_atoms_size = m_atoms_size;
+  rhs.m_atoms_count = m_atoms_count;
+}
+
+void Chapters::Edition::Clear() {
+  while (m_atoms_count > 0) {
+    Atom& a = m_atoms[--m_atoms_count];
+    a.Clear();
+  }
+
+  delete[] m_atoms;
+  m_atoms = NULL;
+
+  m_atoms_size = 0;
+}
+
+long Chapters::Edition::Parse(IMkvReader* pReader, long long pos,
+                              long long size) {
+  const long long stop = pos + size;
+
+  while (pos < stop) {
+    long long id, size;
+
+    long status = ParseElementHeader(pReader, pos, stop, id, size);
+
+    if (status < 0)  // error
+      return status;
+
+    if (size == 0)
+      continue;
+
+    if (id == libwebm::kMkvChapterAtom) {
+      status = ParseAtom(pReader, pos, size);
+
+      if (status < 0)  // error
+        return status;
+    }
+
+    pos += size;
+    if (pos > stop)
+      return E_FILE_FORMAT_INVALID;
+  }
+
+  if (pos != stop)
+    return E_FILE_FORMAT_INVALID;
+  return 0;
+}
+
+long Chapters::Edition::ParseAtom(IMkvReader* pReader, long long pos,
+                                  long long size) {
+  if (!ExpandAtomsArray())
+    return -1;
+
+  Atom& a = m_atoms[m_atoms_count++];
+  a.Init();
+
+  return a.Parse(pReader, pos, size);
+}
+
+bool Chapters::Edition::ExpandAtomsArray() {
+  if (m_atoms_size > m_atoms_count)
+    return true;  // nothing else to do
+
+  const int size = (m_atoms_size == 0) ? 1 : 2 * m_atoms_size;
+
+  Atom* const atoms = new Atom[size];
+
+  for (int idx = 0; idx < m_atoms_count; ++idx) {
+    m_atoms[idx].ShallowCopy(atoms[idx]);
+  }
+
+  delete[] m_atoms;
+  m_atoms = atoms;
+
+  m_atoms_size = size;
+  return true;
+}
+
+Chapters::Atom::Atom() {}
+
+Chapters::Atom::~Atom() {}
+
+unsigned long long Chapters::Atom::GetUID() const { return m_uid; }
+
+const char* Chapters::Atom::GetStringUID() const { return m_string_uid; }
+
+long long Chapters::Atom::GetStartTimecode() const { return m_start_timecode; }
+
+long long Chapters::Atom::GetStopTimecode() const { return m_stop_timecode; }
+
+long long Chapters::Atom::GetStartTime(const Chapters* pChapters) const {
+  return GetTime(pChapters, m_start_timecode);
+}
+
+long long Chapters::Atom::GetStopTime(const Chapters* pChapters) const {
+  return GetTime(pChapters, m_stop_timecode);
+}
+
+int Chapters::Atom::GetDisplayCount() const { return m_displays_count; }
+
+const Chapters::Display* Chapters::Atom::GetDisplay(int index) const {
+  if (index < 0)
+    return NULL;
+
+  if (index >= m_displays_count)
+    return NULL;
+
+  return m_displays + index;
+}
+
+void Chapters::Atom::Init() {
+  m_string_uid = NULL;
+  m_uid = 0;
+  m_start_timecode = -1;
+  m_stop_timecode = -1;
+
+  m_displays = NULL;
+  m_displays_size = 0;
+  m_displays_count = 0;
+}
+
+void Chapters::Atom::ShallowCopy(Atom& rhs) const {
+  rhs.m_string_uid = m_string_uid;
+  rhs.m_uid = m_uid;
+  rhs.m_start_timecode = m_start_timecode;
+  rhs.m_stop_timecode = m_stop_timecode;
+
+  rhs.m_displays = m_displays;
+  rhs.m_displays_size = m_displays_size;
+  rhs.m_displays_count = m_displays_count;
+}
+
+void Chapters::Atom::Clear() {
+  delete[] m_string_uid;
+  m_string_uid = NULL;
+
+  while (m_displays_count > 0) {
+    Display& d = m_displays[--m_displays_count];
+    d.Clear();
+  }
+
+  delete[] m_displays;
+  m_displays = NULL;
+
+  m_displays_size = 0;
+}
+
+long Chapters::Atom::Parse(IMkvReader* pReader, long long pos, long long size) {
+  const long long stop = pos + size;
+
+  while (pos < stop) {
+    long long id, size;
+
+    long status = ParseElementHeader(pReader, pos, stop, id, size);
+
+    if (status < 0)  // error
+      return status;
+
+    if (size == 0)  // 0 length payload, skip.
+      continue;
+
+    if (id == libwebm::kMkvChapterDisplay) {
+      status = ParseDisplay(pReader, pos, size);
+
+      if (status < 0)  // error
+        return status;
+    } else if (id == libwebm::kMkvChapterStringUID) {
+      status = UnserializeString(pReader, pos, size, m_string_uid);
+
+      if (status < 0)  // error
+        return status;
+    } else if (id == libwebm::kMkvChapterUID) {
+      long long val;
+      status = UnserializeInt(pReader, pos, size, val);
+
+      if (status < 0)  // error
+        return status;
+
+      m_uid = static_cast<unsigned long long>(val);
+    } else if (id == libwebm::kMkvChapterTimeStart) {
+      const long long val = UnserializeUInt(pReader, pos, size);
+
+      if (val < 0)  // error
+        return static_cast<long>(val);
+
+      m_start_timecode = val;
+    } else if (id == libwebm::kMkvChapterTimeEnd) {
+      const long long val = UnserializeUInt(pReader, pos, size);
+
+      if (val < 0)  // error
+        return static_cast<long>(val);
+
+      m_stop_timecode = val;
+    }
+
+    pos += size;
+    if (pos > stop)
+      return E_FILE_FORMAT_INVALID;
+  }
+
+  if (pos != stop)
+    return E_FILE_FORMAT_INVALID;
+  return 0;
+}
+
+long long Chapters::Atom::GetTime(const Chapters* pChapters,
+                                  long long timecode) {
+  if (pChapters == NULL)
+    return -1;
+
+  Segment* const pSegment = pChapters->m_pSegment;
+
+  if (pSegment == NULL)  // weird
+    return -1;
+
+  const SegmentInfo* const pInfo = pSegment->GetInfo();
+
+  if (pInfo == NULL)
+    return -1;
+
+  const long long timecode_scale = pInfo->GetTimeCodeScale();
+
+  if (timecode_scale < 1)  // weird
+    return -1;
+
+  if (timecode < 0)
+    return -1;
+
+  const long long result = timecode_scale * timecode;
+
+  return result;
+}
+
+long Chapters::Atom::ParseDisplay(IMkvReader* pReader, long long pos,
+                                  long long size) {
+  if (!ExpandDisplaysArray())
+    return -1;
+
+  Display& d = m_displays[m_displays_count++];
+  d.Init();
+
+  return d.Parse(pReader, pos, size);
+}
+
+bool Chapters::Atom::ExpandDisplaysArray() {
+  if (m_displays_size > m_displays_count)
+    return true;  // nothing else to do
+
+  const int size = (m_displays_size == 0) ? 1 : 2 * m_displays_size;
+
+  Display* const displays = new Display[size];
+
+  for (int idx = 0; idx < m_displays_count; ++idx) {
+    m_displays[idx].ShallowCopy(displays[idx]);
+  }
+
+  delete[] m_displays;
+  m_displays = displays;
+
+  m_displays_size = size;
+  return true;
+}
+
+Chapters::Display::Display() {}
+
+Chapters::Display::~Display() {}
+
+const char* Chapters::Display::GetString() const { return m_string; }
+
+const char* Chapters::Display::GetLanguage() const { return m_language; }
+
+const char* Chapters::Display::GetCountry() const { return m_country; }
+
+void Chapters::Display::Init() {
+  m_string = NULL;
+  m_language = NULL;
+  m_country = NULL;
+}
+
+void Chapters::Display::ShallowCopy(Display& rhs) const {
+  rhs.m_string = m_string;
+  rhs.m_language = m_language;
+  rhs.m_country = m_country;
+}
+
+void Chapters::Display::Clear() {
+  delete[] m_string;
+  m_string = NULL;
+
+  delete[] m_language;
+  m_language = NULL;
+
+  delete[] m_country;
+  m_country = NULL;
+}
+
+long Chapters::Display::Parse(IMkvReader* pReader, long long pos,
+                              long long size) {
+  const long long stop = pos + size;
+
+  while (pos < stop) {
+    long long id, size;
+
+    long status = ParseElementHeader(pReader, pos, stop, id, size);
+
+    if (status < 0)  // error
+      return status;
+
+    if (size == 0)  // No payload.
+      continue;
+
+    if (id == libwebm::kMkvChapString) {
+      status = UnserializeString(pReader, pos, size, m_string);
+
+      if (status)
+        return status;
+    } else if (id == libwebm::kMkvChapLanguage) {
+      status = UnserializeString(pReader, pos, size, m_language);
+
+      if (status)
+        return status;
+    } else if (id == libwebm::kMkvChapCountry) {
+      status = UnserializeString(pReader, pos, size, m_country);
+
+      if (status)
+        return status;
+    }
+
+    pos += size;
+    if (pos > stop)
+      return E_FILE_FORMAT_INVALID;
+  }
+
+  if (pos != stop)
+    return E_FILE_FORMAT_INVALID;
+  return 0;
+}
+
+Tags::Tags(Segment* pSegment, long long payload_start, long long payload_size,
+           long long element_start, long long element_size)
+    : m_pSegment(pSegment),
+      m_start(payload_start),
+      m_size(payload_size),
+      m_element_start(element_start),
+      m_element_size(element_size),
+      m_tags(NULL),
+      m_tags_size(0),
+      m_tags_count(0) {}
+
+Tags::~Tags() {
+  while (m_tags_count > 0) {
+    Tag& t = m_tags[--m_tags_count];
+    t.Clear();
+  }
+  delete[] m_tags;
+}
+
+long Tags::Parse() {
+  IMkvReader* const pReader = m_pSegment->m_pReader;
+
+  long long pos = m_start;  // payload start
+  const long long stop = pos + m_size;  // payload stop
+
+  while (pos < stop) {
+    long long id, size;
+
+    long status = ParseElementHeader(pReader, pos, stop, id, size);
+
+    if (status < 0)
+      return status;
+
+    if (size == 0)  // 0 length tag, read another
+      continue;
+
+    if (id == libwebm::kMkvTag) {
+      status = ParseTag(pos, size);
+
+      if (status < 0)
+        return status;
+    }
+
+    pos += size;
+    if (pos > stop)
+      return E_FILE_FORMAT_INVALID;
+  }
+
+  if (pos != stop)
+    return E_FILE_FORMAT_INVALID;
+
+  return 0;
+}
+
+int Tags::GetTagCount() const { return m_tags_count; }
+
+const Tags::Tag* Tags::GetTag(int idx) const {
+  if (idx < 0)
+    return NULL;
+
+  if (idx >= m_tags_count)
+    return NULL;
+
+  return m_tags + idx;
+}
+
+bool Tags::ExpandTagsArray() {
+  if (m_tags_size > m_tags_count)
+    return true;  // nothing else to do
+
+  const int size = (m_tags_size == 0) ? 1 : 2 * m_tags_size;
+
+  Tag* const tags = new Tag[size];
+
+  for (int idx = 0; idx < m_tags_count; ++idx) {
+    m_tags[idx].ShallowCopy(tags[idx]);
+  }
+
+  delete[] m_tags;
+  m_tags = tags;
+
+  m_tags_size = size;
+  return true;
+}
+
+long Tags::ParseTag(long long pos, long long size) {
+  if (!ExpandTagsArray())
+    return -1;
+
+  Tag& t = m_tags[m_tags_count++];
+  t.Init();
+
+  return t.Parse(m_pSegment->m_pReader, pos, size);
+}
+
+Tags::Tag::Tag() {}
+
+Tags::Tag::~Tag() {}
+
+int Tags::Tag::GetSimpleTagCount() const { return m_simple_tags_count; }
+
+const Tags::SimpleTag* Tags::Tag::GetSimpleTag(int index) const {
+  if (index < 0)
+    return NULL;
+
+  if (index >= m_simple_tags_count)
+    return NULL;
+
+  return m_simple_tags + index;
+}
+
+void Tags::Tag::Init() {
+  m_simple_tags = NULL;
+  m_simple_tags_size = 0;
+  m_simple_tags_count = 0;
+}
+
+void Tags::Tag::ShallowCopy(Tag& rhs) const {
+  rhs.m_simple_tags = m_simple_tags;
+  rhs.m_simple_tags_size = m_simple_tags_size;
+  rhs.m_simple_tags_count = m_simple_tags_count;
+}
+
+void Tags::Tag::Clear() {
+  while (m_simple_tags_count > 0) {
+    SimpleTag& d = m_simple_tags[--m_simple_tags_count];
+    d.Clear();
+  }
+
+  delete[] m_simple_tags;
+  m_simple_tags = NULL;
+
+  m_simple_tags_size = 0;
+}
+
+long Tags::Tag::Parse(IMkvReader* pReader, long long pos, long long size) {
+  const long long stop = pos + size;
+
+  while (pos < stop) {
+    long long id, size;
+
+    long status = ParseElementHeader(pReader, pos, stop, id, size);
+
+    if (status < 0)
+      return status;
+
+    if (size == 0)  // 0 length tag, read another
+      continue;
+
+    if (id == libwebm::kMkvSimpleTag) {
+      status = ParseSimpleTag(pReader, pos, size);
+
+      if (status < 0)
+        return status;
+    }
+
+    pos += size;
+    if (pos > stop)
+      return E_FILE_FORMAT_INVALID;
+  }
+
+  if (pos != stop)
+    return E_FILE_FORMAT_INVALID;
+  return 0;
+}
+
+long Tags::Tag::ParseSimpleTag(IMkvReader* pReader, long long pos,
+                               long long size) {
+  if (!ExpandSimpleTagsArray())
+    return -1;
+
+  SimpleTag& st = m_simple_tags[m_simple_tags_count++];
+  st.Init();
+
+  return st.Parse(pReader, pos, size);
+}
+
+bool Tags::Tag::ExpandSimpleTagsArray() {
+  if (m_simple_tags_size > m_simple_tags_count)
+    return true;  // nothing else to do
+
+  const int size = (m_simple_tags_size == 0) ? 1 : 2 * m_simple_tags_size;
+
+  SimpleTag* const displays = new SimpleTag[size];
+
+  for (int idx = 0; idx < m_simple_tags_count; ++idx) {
+    m_simple_tags[idx].ShallowCopy(displays[idx]);
+  }
+
+  delete[] m_simple_tags;
+  m_simple_tags = displays;
+
+  m_simple_tags_size = size;
+  return true;
+}
+
+Tags::SimpleTag::SimpleTag() {}
+
+Tags::SimpleTag::~SimpleTag() {}
+
+const char* Tags::SimpleTag::GetTagName() const { return m_tag_name; }
+
+const char* Tags::SimpleTag::GetTagString() const { return m_tag_string; }
+
+void Tags::SimpleTag::Init() {
+  m_tag_name = NULL;
+  m_tag_string = NULL;
+}
+
+void Tags::SimpleTag::ShallowCopy(SimpleTag& rhs) const {
+  rhs.m_tag_name = m_tag_name;
+  rhs.m_tag_string = m_tag_string;
+}
+
+void Tags::SimpleTag::Clear() {
+  delete[] m_tag_name;
+  m_tag_name = NULL;
+
+  delete[] m_tag_string;
+  m_tag_string = NULL;
+}
+
+long Tags::SimpleTag::Parse(IMkvReader* pReader, long long pos,
+                            long long size) {
+  const long long stop = pos + size;
+
+  while (pos < stop) {
+    long long id, size;
+
+    long status = ParseElementHeader(pReader, pos, stop, id, size);
+
+    if (status < 0)  // error
+      return status;
+
+    if (size == 0)  // weird
+      continue;
+
+    if (id == libwebm::kMkvTagName) {
+      status = UnserializeString(pReader, pos, size, m_tag_name);
+
+      if (status)
+        return status;
+    } else if (id == libwebm::kMkvTagString) {
+      status = UnserializeString(pReader, pos, size, m_tag_string);
+
+      if (status)
+        return status;
+    }
+
+    pos += size;
+    if (pos > stop)
+      return E_FILE_FORMAT_INVALID;
+  }
+
+  if (pos != stop)
+    return E_FILE_FORMAT_INVALID;
+  return 0;
+}
+
+SegmentInfo::SegmentInfo(Segment* pSegment, long long start, long long size_,
+                         long long element_start, long long element_size)
+    : m_pSegment(pSegment),
+      m_start(start),
+      m_size(size_),
+      m_element_start(element_start),
+      m_element_size(element_size),
+      m_pMuxingAppAsUTF8(NULL),
+      m_pWritingAppAsUTF8(NULL),
+      m_pTitleAsUTF8(NULL) {}
+
+SegmentInfo::~SegmentInfo() {
+  delete[] m_pMuxingAppAsUTF8;
+  m_pMuxingAppAsUTF8 = NULL;
+
+  delete[] m_pWritingAppAsUTF8;
+  m_pWritingAppAsUTF8 = NULL;
+
+  delete[] m_pTitleAsUTF8;
+  m_pTitleAsUTF8 = NULL;
+}
+
+long SegmentInfo::Parse() {
+  assert(m_pMuxingAppAsUTF8 == NULL);
+  assert(m_pWritingAppAsUTF8 == NULL);
+  assert(m_pTitleAsUTF8 == NULL);
+
+  IMkvReader* const pReader = m_pSegment->m_pReader;
+
+  long long pos = m_start;
+  const long long stop = m_start + m_size;
+
+  m_timecodeScale = 1000000;
+  m_duration = -1;
+
+  while (pos < stop) {
+    long long id, size;
+
+    const long status = ParseElementHeader(pReader, pos, stop, id, size);
+
+    if (status < 0)  // error
+      return status;
+
+    if (id == libwebm::kMkvTimecodeScale) {
+      m_timecodeScale = UnserializeUInt(pReader, pos, size);
+
+      if (m_timecodeScale <= 0)
+        return E_FILE_FORMAT_INVALID;
+    } else if (id == libwebm::kMkvDuration) {
+      const long status = UnserializeFloat(pReader, pos, size, m_duration);
+
+      if (status < 0)
+        return status;
+
+      if (m_duration < 0)
+        return E_FILE_FORMAT_INVALID;
+    } else if (id == libwebm::kMkvMuxingApp) {
+      const long status =
+          UnserializeString(pReader, pos, size, m_pMuxingAppAsUTF8);
+
+      if (status)
+        return status;
+    } else if (id == libwebm::kMkvWritingApp) {
+      const long status =
+          UnserializeString(pReader, pos, size, m_pWritingAppAsUTF8);
+
+      if (status)
+        return status;
+    } else if (id == libwebm::kMkvTitle) {
+      const long status = UnserializeString(pReader, pos, size, m_pTitleAsUTF8);
+
+      if (status)
+        return status;
+    }
+
+    pos += size;
+
+    if (pos > stop)
+      return E_FILE_FORMAT_INVALID;
+  }
+
+  const double rollover_check = m_duration * m_timecodeScale;
+  if (rollover_check > LLONG_MAX)
+    return E_FILE_FORMAT_INVALID;
+
+  if (pos != stop)
+    return E_FILE_FORMAT_INVALID;
+
+  return 0;
+}
+
+long long SegmentInfo::GetTimeCodeScale() const { return m_timecodeScale; }
+
+long long SegmentInfo::GetDuration() const {
+  if (m_duration < 0)
+    return -1;
+
+  assert(m_timecodeScale >= 1);
+
+  const double dd = double(m_duration) * double(m_timecodeScale);
+  const long long d = static_cast<long long>(dd);
+
+  return d;
+}
+
+const char* SegmentInfo::GetMuxingAppAsUTF8() const {
+  return m_pMuxingAppAsUTF8;
+}
+
+const char* SegmentInfo::GetWritingAppAsUTF8() const {
+  return m_pWritingAppAsUTF8;
+}
+
+const char* SegmentInfo::GetTitleAsUTF8() const { return m_pTitleAsUTF8; }
+
+///////////////////////////////////////////////////////////////
+// ContentEncoding element
+ContentEncoding::ContentCompression::ContentCompression()
+    : algo(0), settings(NULL), settings_len(0) {}
+
+ContentEncoding::ContentCompression::~ContentCompression() {
+  delete[] settings;
+}
+
+ContentEncoding::ContentEncryption::ContentEncryption()
+    : algo(0),
+      key_id(NULL),
+      key_id_len(0),
+      signature(NULL),
+      signature_len(0),
+      sig_key_id(NULL),
+      sig_key_id_len(0),
+      sig_algo(0),
+      sig_hash_algo(0) {}
+
+ContentEncoding::ContentEncryption::~ContentEncryption() {
+  delete[] key_id;
+  delete[] signature;
+  delete[] sig_key_id;
+}
+
+ContentEncoding::ContentEncoding()
+    : compression_entries_(NULL),
+      compression_entries_end_(NULL),
+      encryption_entries_(NULL),
+      encryption_entries_end_(NULL),
+      encoding_order_(0),
+      encoding_scope_(1),
+      encoding_type_(0) {}
+
+ContentEncoding::~ContentEncoding() {
+  ContentCompression** comp_i = compression_entries_;
+  ContentCompression** const comp_j = compression_entries_end_;
+
+  while (comp_i != comp_j) {
+    ContentCompression* const comp = *comp_i++;
+    delete comp;
+  }
+
+  delete[] compression_entries_;
+
+  ContentEncryption** enc_i = encryption_entries_;
+  ContentEncryption** const enc_j = encryption_entries_end_;
+
+  while (enc_i != enc_j) {
+    ContentEncryption* const enc = *enc_i++;
+    delete enc;
+  }
+
+  delete[] encryption_entries_;
+}
+
+const ContentEncoding::ContentCompression*
+    ContentEncoding::GetCompressionByIndex(unsigned long idx) const {
+  const ptrdiff_t count = compression_entries_end_ - compression_entries_;
+  assert(count >= 0);
+
+  if (idx >= static_cast<unsigned long>(count))
+    return NULL;
+
+  return compression_entries_[idx];
+}
+
+unsigned long ContentEncoding::GetCompressionCount() const {
+  const ptrdiff_t count = compression_entries_end_ - compression_entries_;
+  assert(count >= 0);
+
+  return static_cast<unsigned long>(count);
+}
+
+const ContentEncoding::ContentEncryption* ContentEncoding::GetEncryptionByIndex(
+    unsigned long idx) const {
+  const ptrdiff_t count = encryption_entries_end_ - encryption_entries_;
+  assert(count >= 0);
+
+  if (idx >= static_cast<unsigned long>(count))
+    return NULL;
+
+  return encryption_entries_[idx];
+}
+
+unsigned long ContentEncoding::GetEncryptionCount() const {
+  const ptrdiff_t count = encryption_entries_end_ - encryption_entries_;
+  assert(count >= 0);
+
+  return static_cast<unsigned long>(count);
+}
+
+long ContentEncoding::ParseContentEncAESSettingsEntry(
+    long long start, long long size, IMkvReader* pReader,
+    ContentEncAESSettings* aes) {
+  assert(pReader);
+  assert(aes);
+
+  long long pos = start;
+  const long long stop = start + size;
+
+  while (pos < stop) {
+    long long id, size;
+    const long status = ParseElementHeader(pReader, pos, stop, id, size);
+    if (status < 0)  // error
+      return status;
+
+    if (id == libwebm::kMkvAESSettingsCipherMode) {
+      aes->cipher_mode = UnserializeUInt(pReader, pos, size);
+      if (aes->cipher_mode != 1)
+        return E_FILE_FORMAT_INVALID;
+    }
+
+    pos += size;  // consume payload
+    if (pos > stop)
+      return E_FILE_FORMAT_INVALID;
+  }
+
+  return 0;
+}
+
+long ContentEncoding::ParseContentEncodingEntry(long long start, long long size,
+                                                IMkvReader* pReader) {
+  assert(pReader);
+
+  long long pos = start;
+  const long long stop = start + size;
+
+  // Count ContentCompression and ContentEncryption elements.
+  int compression_count = 0;
+  int encryption_count = 0;
+
+  while (pos < stop) {
+    long long id, size;
+    const long status = ParseElementHeader(pReader, pos, stop, id, size);
+    if (status < 0)  // error
+      return status;
+
+    if (id == libwebm::kMkvContentCompression)
+      ++compression_count;
+
+    if (id == libwebm::kMkvContentEncryption)
+      ++encryption_count;
+
+    pos += size;  // consume payload
+    if (pos > stop)
+      return E_FILE_FORMAT_INVALID;
+  }
+
+  if (compression_count <= 0 && encryption_count <= 0)
+    return -1;
+
+  if (compression_count > 0) {
+    compression_entries_ = new ContentCompression*[compression_count];
+    compression_entries_end_ = compression_entries_;
+  }
+
+  if (encryption_count > 0) {
+    encryption_entries_ = new ContentEncryption*[encryption_count];
+    encryption_entries_end_ = encryption_entries_;
+  }
+
+  pos = start;
+  while (pos < stop) {
+    long long id, size;
+    long status = ParseElementHeader(pReader, pos, stop, id, size);
+    if (status < 0)  // error
+      return status;
+
+    if (id == libwebm::kMkvContentEncodingOrder) {
+      encoding_order_ = UnserializeUInt(pReader, pos, size);
+    } else if (id == libwebm::kMkvContentEncodingScope) {
+      encoding_scope_ = UnserializeUInt(pReader, pos, size);
+      if (encoding_scope_ < 1)
+        return -1;
+    } else if (id == libwebm::kMkvContentEncodingType) {
+      encoding_type_ = UnserializeUInt(pReader, pos, size);
+    } else if (id == libwebm::kMkvContentCompression) {
+      ContentCompression* const compression = new ContentCompression();
+
+      status = ParseCompressionEntry(pos, size, pReader, compression);
+      if (status) {
+        delete compression;
+        return status;
+      }
+      *compression_entries_end_++ = compression;
+    } else if (id == libwebm::kMkvContentEncryption) {
+      ContentEncryption* const encryption = new ContentEncryption();
+
+      status = ParseEncryptionEntry(pos, size, pReader, encryption);
+      if (status) {
+        delete encryption;
+        return status;
+      }
+      *encryption_entries_end_++ = encryption;
+    }
+
+    pos += size;  // consume payload
+    if (pos > stop)
+      return E_FILE_FORMAT_INVALID;
+  }
+
+  if (pos != stop)
+    return E_FILE_FORMAT_INVALID;
+  return 0;
+}
+
+long ContentEncoding::ParseCompressionEntry(long long start, long long size,
+                                            IMkvReader* pReader,
+                                            ContentCompression* compression) {
+  assert(pReader);
+  assert(compression);
+
+  long long pos = start;
+  const long long stop = start + size;
+
+  bool valid = false;
+
+  while (pos < stop) {
+    long long id, size;
+    const long status = ParseElementHeader(pReader, pos, stop, id, size);
+    if (status < 0)  // error
+      return status;
+
+    if (id == libwebm::kMkvContentCompAlgo) {
+      long long algo = UnserializeUInt(pReader, pos, size);
+      if (algo < 0)
+        return E_FILE_FORMAT_INVALID;
+      compression->algo = algo;
+      valid = true;
+    } else if (id == libwebm::kMkvContentCompSettings) {
+      if (size <= 0)
+        return E_FILE_FORMAT_INVALID;
+
+      const size_t buflen = static_cast<size_t>(size);
+      unsigned char* buf = SafeArrayAlloc<unsigned char>(1, buflen);
+      if (buf == NULL)
+        return -1;
+
+      const int read_status =
+          pReader->Read(pos, static_cast<long>(buflen), buf);
+      if (read_status) {
+        delete[] buf;
+        return status;
+      }
+
+      compression->settings = buf;
+      compression->settings_len = buflen;
+    }
+
+    pos += size;  // consume payload
+    if (pos > stop)
+      return E_FILE_FORMAT_INVALID;
+  }
+
+  // ContentCompAlgo is mandatory
+  if (!valid)
+    return E_FILE_FORMAT_INVALID;
+
+  return 0;
+}
+
+long ContentEncoding::ParseEncryptionEntry(long long start, long long size,
+                                           IMkvReader* pReader,
+                                           ContentEncryption* encryption) {
+  assert(pReader);
+  assert(encryption);
+
+  long long pos = start;
+  const long long stop = start + size;
+
+  while (pos < stop) {
+    long long id, size;
+    const long status = ParseElementHeader(pReader, pos, stop, id, size);
+    if (status < 0)  // error
+      return status;
+
+    if (id == libwebm::kMkvContentEncAlgo) {
+      encryption->algo = UnserializeUInt(pReader, pos, size);
+      if (encryption->algo != 5)
+        return E_FILE_FORMAT_INVALID;
+    } else if (id == libwebm::kMkvContentEncKeyID) {
+      delete[] encryption->key_id;
+      encryption->key_id = NULL;
+      encryption->key_id_len = 0;
+
+      if (size <= 0)
+        return E_FILE_FORMAT_INVALID;
+
+      const size_t buflen = static_cast<size_t>(size);
+      unsigned char* buf = SafeArrayAlloc<unsigned char>(1, buflen);
+      if (buf == NULL)
+        return -1;
+
+      const int read_status =
+          pReader->Read(pos, static_cast<long>(buflen), buf);
+      if (read_status) {
+        delete[] buf;
+        return status;
+      }
+
+      encryption->key_id = buf;
+      encryption->key_id_len = buflen;
+    } else if (id == libwebm::kMkvContentSignature) {
+      delete[] encryption->signature;
+      encryption->signature = NULL;
+      encryption->signature_len = 0;
+
+      if (size <= 0)
+        return E_FILE_FORMAT_INVALID;
+
+      const size_t buflen = static_cast<size_t>(size);
+      unsigned char* buf = SafeArrayAlloc<unsigned char>(1, buflen);
+      if (buf == NULL)
+        return -1;
+
+      const int read_status =
+          pReader->Read(pos, static_cast<long>(buflen), buf);
+      if (read_status) {
+        delete[] buf;
+        return status;
+      }
+
+      encryption->signature = buf;
+      encryption->signature_len = buflen;
+    } else if (id == libwebm::kMkvContentSigKeyID) {
+      delete[] encryption->sig_key_id;
+      encryption->sig_key_id = NULL;
+      encryption->sig_key_id_len = 0;
+
+      if (size <= 0)
+        return E_FILE_FORMAT_INVALID;
+
+      const size_t buflen = static_cast<size_t>(size);
+      unsigned char* buf = SafeArrayAlloc<unsigned char>(1, buflen);
+      if (buf == NULL)
+        return -1;
+
+      const int read_status =
+          pReader->Read(pos, static_cast<long>(buflen), buf);
+      if (read_status) {
+        delete[] buf;
+        return status;
+      }
+
+      encryption->sig_key_id = buf;
+      encryption->sig_key_id_len = buflen;
+    } else if (id == libwebm::kMkvContentSigAlgo) {
+      encryption->sig_algo = UnserializeUInt(pReader, pos, size);
+    } else if (id == libwebm::kMkvContentSigHashAlgo) {
+      encryption->sig_hash_algo = UnserializeUInt(pReader, pos, size);
+    } else if (id == libwebm::kMkvContentEncAESSettings) {
+      const long status = ParseContentEncAESSettingsEntry(
+          pos, size, pReader, &encryption->aes_settings);
+      if (status)
+        return status;
+    }
+
+    pos += size;  // consume payload
+    if (pos > stop)
+      return E_FILE_FORMAT_INVALID;
+  }
+
+  return 0;
+}
+
+Track::Track(Segment* pSegment, long long element_start, long long element_size)
+    : m_pSegment(pSegment),
+      m_element_start(element_start),
+      m_element_size(element_size),
+      content_encoding_entries_(NULL),
+      content_encoding_entries_end_(NULL) {}
+
+Track::~Track() {
+  Info& info = const_cast<Info&>(m_info);
+  info.Clear();
+
+  ContentEncoding** i = content_encoding_entries_;
+  ContentEncoding** const j = content_encoding_entries_end_;
+
+  while (i != j) {
+    ContentEncoding* const encoding = *i++;
+    delete encoding;
+  }
+
+  delete[] content_encoding_entries_;
+}
+
+long Track::Create(Segment* pSegment, const Info& info, long long element_start,
+                   long long element_size, Track*& pResult) {
+  if (pResult)
+    return -1;
+
+  Track* const pTrack = new Track(pSegment, element_start, element_size);
+
+  const int status = info.Copy(pTrack->m_info);
+
+  if (status) {  // error
+    delete pTrack;
+    return status;
+  }
+
+  pResult = pTrack;
+  return 0;  // success
+}
+
+Track::Info::Info()
+    : uid(0),
+      defaultDuration(0),
+      codecDelay(0),
+      seekPreRoll(0),
+      nameAsUTF8(NULL),
+      language(NULL),
+      codecId(NULL),
+      codecNameAsUTF8(NULL),
+      codecPrivate(NULL),
+      codecPrivateSize(0),
+      lacing(false) {}
+
+Track::Info::~Info() { Clear(); }
+
+void Track::Info::Clear() {
+  delete[] nameAsUTF8;
+  nameAsUTF8 = NULL;
+
+  delete[] language;
+  language = NULL;
+
+  delete[] codecId;
+  codecId = NULL;
+
+  delete[] codecPrivate;
+  codecPrivate = NULL;
+  codecPrivateSize = 0;
+
+  delete[] codecNameAsUTF8;
+  codecNameAsUTF8 = NULL;
+}
+
+int Track::Info::CopyStr(char* Info::*str, Info& dst_) const {
+  if (str == static_cast<char * Info::*>(NULL))
+    return -1;
+
+  char*& dst = dst_.*str;
+
+  if (dst)  // should be NULL already
+    return -1;
+
+  const char* const src = this->*str;
+
+  if (src == NULL)
+    return 0;
+
+  const size_t len = strlen(src);
+
+  dst = SafeArrayAlloc<char>(1, len + 1);
+
+  if (dst == NULL)
+    return -1;
+
+  strcpy(dst, src);
+
+  return 0;
+}
+
+int Track::Info::Copy(Info& dst) const {
+  if (&dst == this)
+    return 0;
+
+  dst.type = type;
+  dst.number = number;
+  dst.defaultDuration = defaultDuration;
+  dst.codecDelay = codecDelay;
+  dst.seekPreRoll = seekPreRoll;
+  dst.uid = uid;
+  dst.lacing = lacing;
+  dst.settings = settings;
+
+  // We now copy the string member variables from src to dst.
+  // This involves memory allocation so in principle the operation
+  // can fail (indeed, that's why we have Info::Copy), so we must
+  // report this to the caller.  An error return from this function
+  // therefore implies that the copy was only partially successful.
+
+  if (int status = CopyStr(&Info::nameAsUTF8, dst))
+    return status;
+
+  if (int status = CopyStr(&Info::language, dst))
+    return status;
+
+  if (int status = CopyStr(&Info::codecId, dst))
+    return status;
+
+  if (int status = CopyStr(&Info::codecNameAsUTF8, dst))
+    return status;
+
+  if (codecPrivateSize > 0) {
+    if (codecPrivate == NULL)
+      return -1;
+
+    if (dst.codecPrivate)
+      return -1;
+
+    if (dst.codecPrivateSize != 0)
+      return -1;
+
+    dst.codecPrivate = SafeArrayAlloc<unsigned char>(1, codecPrivateSize);
+
+    if (dst.codecPrivate == NULL)
+      return -1;
+
+    memcpy(dst.codecPrivate, codecPrivate, codecPrivateSize);
+    dst.codecPrivateSize = codecPrivateSize;
+  }
+
+  return 0;
+}
+
+const BlockEntry* Track::GetEOS() const { return &m_eos; }
+
+long Track::GetType() const { return m_info.type; }
+
+long Track::GetNumber() const { return m_info.number; }
+
+unsigned long long Track::GetUid() const { return m_info.uid; }
+
+const char* Track::GetNameAsUTF8() const { return m_info.nameAsUTF8; }
+
+const char* Track::GetLanguage() const { return m_info.language; }
+
+const char* Track::GetCodecNameAsUTF8() const { return m_info.codecNameAsUTF8; }
+
+const char* Track::GetCodecId() const { return m_info.codecId; }
+
+const unsigned char* Track::GetCodecPrivate(size_t& size) const {
+  size = m_info.codecPrivateSize;
+  return m_info.codecPrivate;
+}
+
+bool Track::GetLacing() const { return m_info.lacing; }
+
+unsigned long long Track::GetDefaultDuration() const {
+  return m_info.defaultDuration;
+}
+
+unsigned long long Track::GetCodecDelay() const { return m_info.codecDelay; }
+
+unsigned long long Track::GetSeekPreRoll() const { return m_info.seekPreRoll; }
+
+long Track::GetFirst(const BlockEntry*& pBlockEntry) const {
+  const Cluster* pCluster = m_pSegment->GetFirst();
+
+  for (int i = 0;;) {
+    if (pCluster == NULL) {
+      pBlockEntry = GetEOS();
+      return 1;
+    }
+
+    if (pCluster->EOS()) {
+      if (m_pSegment->DoneParsing()) {
+        pBlockEntry = GetEOS();
+        return 1;
+      }
+
+      pBlockEntry = 0;
+      return E_BUFFER_NOT_FULL;
+    }
+
+    long status = pCluster->GetFirst(pBlockEntry);
+
+    if (status < 0)  // error
+      return status;
+
+    if (pBlockEntry == 0) {  // empty cluster
+      pCluster = m_pSegment->GetNext(pCluster);
+      continue;
+    }
+
+    for (;;) {
+      const Block* const pBlock = pBlockEntry->GetBlock();
+      assert(pBlock);
+
+      const long long tn = pBlock->GetTrackNumber();
+
+      if ((tn == m_info.number) && VetEntry(pBlockEntry))
+        return 0;
+
+      const BlockEntry* pNextEntry;
+
+      status = pCluster->GetNext(pBlockEntry, pNextEntry);
+
+      if (status < 0)  // error
+        return status;
+
+      if (pNextEntry == 0)
+        break;
+
+      pBlockEntry = pNextEntry;
+    }
+
+    ++i;
+
+    if (i >= 100)
+      break;
+
+    pCluster = m_pSegment->GetNext(pCluster);
+  }
+
+  // NOTE: if we get here, it means that we didn't find a block with
+  // a matching track number.  We interpret that as an error (which
+  // might be too conservative).
+
+  pBlockEntry = GetEOS();  // so we can return a non-NULL value
+  return 1;
+}
+
+long Track::GetNext(const BlockEntry* pCurrEntry,
+                    const BlockEntry*& pNextEntry) const {
+  assert(pCurrEntry);
+  assert(!pCurrEntry->EOS());  //?
+
+  const Block* const pCurrBlock = pCurrEntry->GetBlock();
+  assert(pCurrBlock && pCurrBlock->GetTrackNumber() == m_info.number);
+  if (!pCurrBlock || pCurrBlock->GetTrackNumber() != m_info.number)
+    return -1;
+
+  const Cluster* pCluster = pCurrEntry->GetCluster();
+  assert(pCluster);
+  assert(!pCluster->EOS());
+
+  long status = pCluster->GetNext(pCurrEntry, pNextEntry);
+
+  if (status < 0)  // error
+    return status;
+
+  for (int i = 0;;) {
+    while (pNextEntry) {
+      const Block* const pNextBlock = pNextEntry->GetBlock();
+      assert(pNextBlock);
+
+      if (pNextBlock->GetTrackNumber() == m_info.number)
+        return 0;
+
+      pCurrEntry = pNextEntry;
+
+      status = pCluster->GetNext(pCurrEntry, pNextEntry);
+
+      if (status < 0)  // error
+        return status;
+    }
+
+    pCluster = m_pSegment->GetNext(pCluster);
+
+    if (pCluster == NULL) {
+      pNextEntry = GetEOS();
+      return 1;
+    }
+
+    if (pCluster->EOS()) {
+      if (m_pSegment->DoneParsing()) {
+        pNextEntry = GetEOS();
+        return 1;
+      }
+
+      // TODO: there is a potential O(n^2) problem here: we tell the
+      // caller to (pre)load another cluster, which he does, but then he
+      // calls GetNext again, which repeats the same search.  This is
+      // a pathological case, since the only way it can happen is if
+      // there exists a long sequence of clusters none of which contain a
+      // block from this track.  One way around this problem is for the
+      // caller to be smarter when he loads another cluster: don't call
+      // us back until you have a cluster that contains a block from this
+      // track. (Of course, that's not cheap either, since our caller
+      // would have to scan the each cluster as it's loaded, so that
+      // would just push back the problem.)
+
+      pNextEntry = NULL;
+      return E_BUFFER_NOT_FULL;
+    }
+
+    status = pCluster->GetFirst(pNextEntry);
+
+    if (status < 0)  // error
+      return status;
+
+    if (pNextEntry == NULL)  // empty cluster
+      continue;
+
+    ++i;
+
+    if (i >= 100)
+      break;
+  }
+
+  // NOTE: if we get here, it means that we didn't find a block with
+  // a matching track number after lots of searching, so we give
+  // up trying.
+
+  pNextEntry = GetEOS();  // so we can return a non-NULL value
+  return 1;
+}
+
+bool Track::VetEntry(const BlockEntry* pBlockEntry) const {
+  assert(pBlockEntry);
+  const Block* const pBlock = pBlockEntry->GetBlock();
+  assert(pBlock);
+  assert(pBlock->GetTrackNumber() == m_info.number);
+  if (!pBlock || pBlock->GetTrackNumber() != m_info.number)
+    return false;
+
+  // This function is used during a seek to determine whether the
+  // frame is a valid seek target.  This default function simply
+  // returns true, which means all frames are valid seek targets.
+  // It gets overridden by the VideoTrack class, because only video
+  // keyframes can be used as seek target.
+
+  return true;
+}
+
+long Track::Seek(long long time_ns, const BlockEntry*& pResult) const {
+  const long status = GetFirst(pResult);
+
+  if (status < 0)  // buffer underflow, etc
+    return status;
+
+  assert(pResult);
+
+  if (pResult->EOS())
+    return 0;
+
+  const Cluster* pCluster = pResult->GetCluster();
+  assert(pCluster);
+  assert(pCluster->GetIndex() >= 0);
+
+  if (time_ns <= pResult->GetBlock()->GetTime(pCluster))
+    return 0;
+
+  Cluster** const clusters = m_pSegment->m_clusters;
+  assert(clusters);
+
+  const long count = m_pSegment->GetCount();  // loaded only, not preloaded
+  assert(count > 0);
+
+  Cluster** const i = clusters + pCluster->GetIndex();
+  assert(i);
+  assert(*i == pCluster);
+  assert(pCluster->GetTime() <= time_ns);
+
+  Cluster** const j = clusters + count;
+
+  Cluster** lo = i;
+  Cluster** hi = j;
+
+  while (lo < hi) {
+    // INVARIANT:
+    //[i, lo) <= time_ns
+    //[lo, hi) ?
+    //[hi, j)  > time_ns
+
+    Cluster** const mid = lo + (hi - lo) / 2;
+    assert(mid < hi);
+
+    pCluster = *mid;
+    assert(pCluster);
+    assert(pCluster->GetIndex() >= 0);
+    assert(pCluster->GetIndex() == long(mid - m_pSegment->m_clusters));
+
+    const long long t = pCluster->GetTime();
+
+    if (t <= time_ns)
+      lo = mid + 1;
+    else
+      hi = mid;
+
+    assert(lo <= hi);
+  }
+
+  assert(lo == hi);
+  assert(lo > i);
+  assert(lo <= j);
+
+  while (lo > i) {
+    pCluster = *--lo;
+    assert(pCluster);
+    assert(pCluster->GetTime() <= time_ns);
+
+    pResult = pCluster->GetEntry(this);
+
+    if ((pResult != 0) && !pResult->EOS())
+      return 0;
+
+    // landed on empty cluster (no entries)
+  }
+
+  pResult = GetEOS();  // weird
+  return 0;
+}
+
+const ContentEncoding* Track::GetContentEncodingByIndex(
+    unsigned long idx) const {
+  const ptrdiff_t count =
+      content_encoding_entries_end_ - content_encoding_entries_;
+  assert(count >= 0);
+
+  if (idx >= static_cast<unsigned long>(count))
+    return NULL;
+
+  return content_encoding_entries_[idx];
+}
+
+unsigned long Track::GetContentEncodingCount() const {
+  const ptrdiff_t count =
+      content_encoding_entries_end_ - content_encoding_entries_;
+  assert(count >= 0);
+
+  return static_cast<unsigned long>(count);
+}
+
+long Track::ParseContentEncodingsEntry(long long start, long long size) {
+  IMkvReader* const pReader = m_pSegment->m_pReader;
+  assert(pReader);
+
+  long long pos = start;
+  const long long stop = start + size;
+
+  // Count ContentEncoding elements.
+  int count = 0;
+  while (pos < stop) {
+    long long id, size;
+    const long status = ParseElementHeader(pReader, pos, stop, id, size);
+    if (status < 0)  // error
+      return status;
+
+    // pos now designates start of element
+    if (id == libwebm::kMkvContentEncoding)
+      ++count;
+
+    pos += size;  // consume payload
+    if (pos > stop)
+      return E_FILE_FORMAT_INVALID;
+  }
+
+  if (count <= 0)
+    return -1;
+
+  content_encoding_entries_ = new ContentEncoding*[count];
+  content_encoding_entries_end_ = content_encoding_entries_;
+
+  pos = start;
+  while (pos < stop) {
+    long long id, size;
+    long status = ParseElementHeader(pReader, pos, stop, id, size);
+    if (status < 0)  // error
+      return status;
+
+    // pos now designates start of element
+    if (id == libwebm::kMkvContentEncoding) {
+      ContentEncoding* const content_encoding = new ContentEncoding();
+
+      status = content_encoding->ParseContentEncodingEntry(pos, size, pReader);
+      if (status) {
+        delete content_encoding;
+        return status;
+      }
+
+      *content_encoding_entries_end_++ = content_encoding;
+    }
+
+    pos += size;  // consume payload
+    if (pos > stop)
+      return E_FILE_FORMAT_INVALID;
+  }
+
+  if (pos != stop)
+    return E_FILE_FORMAT_INVALID;
+
+  return 0;
+}
+
+Track::EOSBlock::EOSBlock() : BlockEntry(NULL, LONG_MIN) {}
+
+BlockEntry::Kind Track::EOSBlock::GetKind() const { return kBlockEOS; }
+
+const Block* Track::EOSBlock::GetBlock() const { return NULL; }
+
+bool PrimaryChromaticity::Parse(IMkvReader* reader, long long read_pos,
+                                long long value_size, bool is_x,
+                                PrimaryChromaticity** chromaticity) {
+  if (!reader)
+    return false;
+
+  my_auto_ptr<PrimaryChromaticity> chromaticity_ptr(*chromaticity ? *chromaticity : new PrimaryChromaticity());
+
+  float* value = is_x ? &chromaticity_ptr->x : &chromaticity_ptr->y;
+
+  double parser_value = 0;
+  const long long value_parse_status =
+      UnserializeFloat(reader, read_pos, value_size, parser_value);
+
+  *value = static_cast<float>(parser_value);
+
+  if (value_parse_status < 0 || *value < 0.0 || *value > 1.0)
+    return false;
+
+  *chromaticity = chromaticity_ptr.release();
+  return true;
+}
+
+bool MasteringMetadata::Parse(IMkvReader* reader, long long mm_start,
+                              long long mm_size, MasteringMetadata** mm) {
+  if (!reader || *mm)
+    return false;
+
+  my_auto_ptr<MasteringMetadata> mm_ptr(new MasteringMetadata());
+
+  const long long mm_end = mm_start + mm_size;
+  long long read_pos = mm_start;
+
+  while (read_pos < mm_end) {
+    long long child_id = 0;
+    long long child_size = 0;
+
+    const long long status =
+        ParseElementHeader(reader, read_pos, mm_end, child_id, child_size);
+    if (status < 0)
+      return false;
+
+    if (child_id == libwebm::kMkvLuminanceMax) {
+      double value = 0;
+      const long long value_parse_status =
+          UnserializeFloat(reader, read_pos, child_size, value);
+      mm_ptr->luminance_max = static_cast<float>(value);
+      if (value_parse_status < 0 || mm_ptr->luminance_max < 0.0 ||
+          mm_ptr->luminance_max > 9999.99) {
+        return false;
+      }
+    } else if (child_id == libwebm::kMkvLuminanceMin) {
+      double value = 0;
+      const long long value_parse_status =
+          UnserializeFloat(reader, read_pos, child_size, value);
+      mm_ptr->luminance_min = static_cast<float>(value);
+      if (value_parse_status < 0 || mm_ptr->luminance_min < 0.0 ||
+          mm_ptr->luminance_min > 999.9999) {
+        return false;
+      }
+    } else {
+      bool is_x = false;
+      PrimaryChromaticity** chromaticity;
+      switch (child_id) {
+        case libwebm::kMkvPrimaryRChromaticityX:
+        case libwebm::kMkvPrimaryRChromaticityY:
+          is_x = child_id == libwebm::kMkvPrimaryRChromaticityX;
+          chromaticity = &mm_ptr->r;
+          break;
+        case libwebm::kMkvPrimaryGChromaticityX:
+        case libwebm::kMkvPrimaryGChromaticityY:
+          is_x = child_id == libwebm::kMkvPrimaryGChromaticityX;
+          chromaticity = &mm_ptr->g;
+          break;
+        case libwebm::kMkvPrimaryBChromaticityX:
+        case libwebm::kMkvPrimaryBChromaticityY:
+          is_x = child_id == libwebm::kMkvPrimaryBChromaticityX;
+          chromaticity = &mm_ptr->b;
+          break;
+        case libwebm::kMkvWhitePointChromaticityX:
+        case libwebm::kMkvWhitePointChromaticityY:
+          is_x = child_id == libwebm::kMkvWhitePointChromaticityX;
+          chromaticity = &mm_ptr->white_point;
+          break;
+        default:
+          return false;
+      }
+      const bool value_parse_status = PrimaryChromaticity::Parse(
+          reader, read_pos, child_size, is_x, chromaticity);
+      if (!value_parse_status)
+        return false;
+    }
+
+    read_pos += child_size;
+    if (read_pos > mm_end)
+      return false;
+  }
+
+  *mm = mm_ptr.release();
+  return true;
+}
+
+bool Colour::Parse(IMkvReader* reader, long long colour_start,
+                   long long colour_size, Colour** colour) {
+  if (!reader || *colour)
+    return false;
+
+  my_auto_ptr<Colour> colour_ptr(new Colour());
+
+  const long long colour_end = colour_start + colour_size;
+  long long read_pos = colour_start;
+
+  while (read_pos < colour_end) {
+    long long child_id = 0;
+    long long child_size = 0;
+
+    const long status =
+        ParseElementHeader(reader, read_pos, colour_end, child_id, child_size);
+    if (status < 0)
+      return false;
+
+    if (child_id == libwebm::kMkvMatrixCoefficients) {
+      colour_ptr->matrix_coefficients =
+          UnserializeUInt(reader, read_pos, child_size);
+      if (colour_ptr->matrix_coefficients < 0)
+        return false;
+    } else if (child_id == libwebm::kMkvBitsPerChannel) {
+      colour_ptr->bits_per_channel =
+          UnserializeUInt(reader, read_pos, child_size);
+      if (colour_ptr->bits_per_channel < 0)
+        return false;
+    } else if (child_id == libwebm::kMkvChromaSubsamplingHorz) {
+      colour_ptr->chroma_subsampling_horz =
+          UnserializeUInt(reader, read_pos, child_size);
+      if (colour_ptr->chroma_subsampling_horz < 0)
+        return false;
+    } else if (child_id == libwebm::kMkvChromaSubsamplingVert) {
+      colour_ptr->chroma_subsampling_vert =
+          UnserializeUInt(reader, read_pos, child_size);
+      if (colour_ptr->chroma_subsampling_vert < 0)
+        return false;
+    } else if (child_id == libwebm::kMkvCbSubsamplingHorz) {
+      colour_ptr->cb_subsampling_horz =
+          UnserializeUInt(reader, read_pos, child_size);
+      if (colour_ptr->cb_subsampling_horz < 0)
+        return false;
+    } else if (child_id == libwebm::kMkvCbSubsamplingVert) {
+      colour_ptr->cb_subsampling_vert =
+          UnserializeUInt(reader, read_pos, child_size);
+      if (colour_ptr->cb_subsampling_vert < 0)
+        return false;
+    } else if (child_id == libwebm::kMkvChromaSitingHorz) {
+      colour_ptr->chroma_siting_horz =
+          UnserializeUInt(reader, read_pos, child_size);
+      if (colour_ptr->chroma_siting_horz < 0)
+        return false;
+    } else if (child_id == libwebm::kMkvChromaSitingVert) {
+      colour_ptr->chroma_siting_vert =
+          UnserializeUInt(reader, read_pos, child_size);
+      if (colour_ptr->chroma_siting_vert < 0)
+        return false;
+    } else if (child_id == libwebm::kMkvRange) {
+      colour_ptr->range = UnserializeUInt(reader, read_pos, child_size);
+      if (colour_ptr->range < 0)
+        return false;
+    } else if (child_id == libwebm::kMkvTransferCharacteristics) {
+      colour_ptr->transfer_characteristics =
+          UnserializeUInt(reader, read_pos, child_size);
+      if (colour_ptr->transfer_characteristics < 0)
+        return false;
+    } else if (child_id == libwebm::kMkvPrimaries) {
+      colour_ptr->primaries = UnserializeUInt(reader, read_pos, child_size);
+      if (colour_ptr->primaries < 0)
+        return false;
+    } else if (child_id == libwebm::kMkvMaxCLL) {
+      colour_ptr->max_cll = UnserializeUInt(reader, read_pos, child_size);
+      if (colour_ptr->max_cll < 0)
+        return false;
+    } else if (child_id == libwebm::kMkvMaxFALL) {
+      colour_ptr->max_fall = UnserializeUInt(reader, read_pos, child_size);
+      if (colour_ptr->max_fall < 0)
+        return false;
+    } else if (child_id == libwebm::kMkvMasteringMetadata) {
+      if (!MasteringMetadata::Parse(reader, read_pos, child_size,
+                                    &colour_ptr->mastering_metadata))
+        return false;
+    } else {
+      return false;
+    }
+
+    read_pos += child_size;
+    if (read_pos > colour_end)
+      return false;
+  }
+  *colour = colour_ptr.release();
+  return true;
+}
+
+VideoTrack::VideoTrack(Segment* pSegment, long long element_start,
+                       long long element_size)
+    : Track(pSegment, element_start, element_size), m_colour(NULL) {}
+
+VideoTrack::~VideoTrack() { delete m_colour; }
+
+long VideoTrack::Parse(Segment* pSegment, const Info& info,
+                       long long element_start, long long element_size,
+                       VideoTrack*& pResult) {
+  if (pResult)
+    return -1;
+
+  if (info.type != Track::kVideo)
+    return -1;
+
+  long long width = 0;
+  long long height = 0;
+  long long display_width = 0;
+  long long display_height = 0;
+  long long display_unit = 0;
+  long long stereo_mode = 0;
+
+  double rate = 0.0;
+
+  IMkvReader* const pReader = pSegment->m_pReader;
+
+  const Settings& s = info.settings;
+  assert(s.start >= 0);
+  assert(s.size >= 0);
+
+  long long pos = s.start;
+  assert(pos >= 0);
+
+  const long long stop = pos + s.size;
+
+  Colour* colour = NULL;
+
+  while (pos < stop) {
+    long long id, size;
+
+    const long status = ParseElementHeader(pReader, pos, stop, id, size);
+
+    if (status < 0)  // error
+      return status;
+
+    if (id == libwebm::kMkvPixelWidth) {
+      width = UnserializeUInt(pReader, pos, size);
+
+      if (width <= 0)
+        return E_FILE_FORMAT_INVALID;
+    } else if (id == libwebm::kMkvPixelHeight) {
+      height = UnserializeUInt(pReader, pos, size);
+
+      if (height <= 0)
+        return E_FILE_FORMAT_INVALID;
+    } else if (id == libwebm::kMkvDisplayWidth) {
+      display_width = UnserializeUInt(pReader, pos, size);
+
+      if (display_width <= 0)
+        return E_FILE_FORMAT_INVALID;
+    } else if (id == libwebm::kMkvDisplayHeight) {
+      display_height = UnserializeUInt(pReader, pos, size);
+
+      if (display_height <= 0)
+        return E_FILE_FORMAT_INVALID;
+    } else if (id == libwebm::kMkvDisplayUnit) {
+      display_unit = UnserializeUInt(pReader, pos, size);
+
+      if (display_unit < 0)
+        return E_FILE_FORMAT_INVALID;
+    } else if (id == libwebm::kMkvStereoMode) {
+      stereo_mode = UnserializeUInt(pReader, pos, size);
+
+      if (stereo_mode < 0)
+        return E_FILE_FORMAT_INVALID;
+    } else if (id == libwebm::kMkvFrameRate) {
+      const long status = UnserializeFloat(pReader, pos, size, rate);
+
+      if (status < 0)
+        return status;
+
+      if (rate <= 0)
+        return E_FILE_FORMAT_INVALID;
+    } else if (id == libwebm::kMkvColour) {
+      if (!Colour::Parse(pReader, pos, size, &colour))
+        return E_FILE_FORMAT_INVALID;
+    }
+
+    pos += size;  // consume payload
+    if (pos > stop)
+      return E_FILE_FORMAT_INVALID;
+  }
+
+  if (pos != stop)
+    return E_FILE_FORMAT_INVALID;
+
+  VideoTrack* const pTrack = new VideoTrack(pSegment, element_start, element_size);
+
+  const int status = info.Copy(pTrack->m_info);
+
+  if (status) {  // error
+    delete pTrack;
+    return status;
+  }
+
+  pTrack->m_width = width;
+  pTrack->m_height = height;
+  pTrack->m_display_width = display_width;
+  pTrack->m_display_height = display_height;
+  pTrack->m_display_unit = display_unit;
+  pTrack->m_stereo_mode = stereo_mode;
+  pTrack->m_rate = rate;
+  pTrack->m_colour = colour;
+
+  pResult = pTrack;
+  return 0;  // success
+}
+
+bool VideoTrack::VetEntry(const BlockEntry* pBlockEntry) const {
+  return Track::VetEntry(pBlockEntry) && pBlockEntry->GetBlock()->IsKey();
+}
+
+long VideoTrack::Seek(long long time_ns, const BlockEntry*& pResult) const {
+  const long status = GetFirst(pResult);
+
+  if (status < 0)  // buffer underflow, etc
+    return status;
+
+  assert(pResult);
+
+  if (pResult->EOS())
+    return 0;
+
+  const Cluster* pCluster = pResult->GetCluster();
+  assert(pCluster);
+  assert(pCluster->GetIndex() >= 0);
+
+  if (time_ns <= pResult->GetBlock()->GetTime(pCluster))
+    return 0;
+
+  Cluster** const clusters = m_pSegment->m_clusters;
+  assert(clusters);
+
+  const long count = m_pSegment->GetCount();  // loaded only, not pre-loaded
+  assert(count > 0);
+
+  Cluster** const i = clusters + pCluster->GetIndex();
+  assert(i);
+  assert(*i == pCluster);
+  assert(pCluster->GetTime() <= time_ns);
+
+  Cluster** const j = clusters + count;
+
+  Cluster** lo = i;
+  Cluster** hi = j;
+
+  while (lo < hi) {
+    // INVARIANT:
+    //[i, lo) <= time_ns
+    //[lo, hi) ?
+    //[hi, j)  > time_ns
+
+    Cluster** const mid = lo + (hi - lo) / 2;
+    assert(mid < hi);
+
+    pCluster = *mid;
+    assert(pCluster);
+    assert(pCluster->GetIndex() >= 0);
+    assert(pCluster->GetIndex() == long(mid - m_pSegment->m_clusters));
+
+    const long long t = pCluster->GetTime();
+
+    if (t <= time_ns)
+      lo = mid + 1;
+    else
+      hi = mid;
+
+    assert(lo <= hi);
+  }
+
+  assert(lo == hi);
+  assert(lo > i);
+  assert(lo <= j);
+
+  pCluster = *--lo;
+  assert(pCluster);
+  assert(pCluster->GetTime() <= time_ns);
+
+  pResult = pCluster->GetEntry(this, time_ns);
+
+  if ((pResult != 0) && !pResult->EOS())  // found a keyframe
+    return 0;
+
+  while (lo != i) {
+    pCluster = *--lo;
+    assert(pCluster);
+    assert(pCluster->GetTime() <= time_ns);
+
+    pResult = pCluster->GetEntry(this, time_ns);
+
+    if ((pResult != 0) && !pResult->EOS())
+      return 0;
+  }
+
+  // weird: we're on the first cluster, but no keyframe found
+  // should never happen but we must return something anyway
+
+  pResult = GetEOS();
+  return 0;
+}
+
+Colour* VideoTrack::GetColour() const { return m_colour; }
+
+long long VideoTrack::GetWidth() const { return m_width; }
+
+long long VideoTrack::GetHeight() const { return m_height; }
+
+long long VideoTrack::GetDisplayWidth() const {
+  return m_display_width > 0 ? m_display_width : GetWidth();
+}
+
+long long VideoTrack::GetDisplayHeight() const {
+  return m_display_height > 0 ? m_display_height : GetHeight();
+}
+
+long long VideoTrack::GetDisplayUnit() const { return m_display_unit; }
+
+long long VideoTrack::GetStereoMode() const { return m_stereo_mode; }
+
+double VideoTrack::GetFrameRate() const { return m_rate; }
+
+AudioTrack::AudioTrack(Segment* pSegment, long long element_start,
+                       long long element_size)
+    : Track(pSegment, element_start, element_size) {}
+
+long AudioTrack::Parse(Segment* pSegment, const Info& info,
+                       long long element_start, long long element_size,
+                       AudioTrack*& pResult) {
+  if (pResult)
+    return -1;
+
+  if (info.type != Track::kAudio)
+    return -1;
+
+  IMkvReader* const pReader = pSegment->m_pReader;
+
+  const Settings& s = info.settings;
+  assert(s.start >= 0);
+  assert(s.size >= 0);
+
+  long long pos = s.start;
+  assert(pos >= 0);
+
+  const long long stop = pos + s.size;
+
+  double rate = 8000.0;  // MKV default
+  long long channels = 1;
+  long long bit_depth = 0;
+
+  while (pos < stop) {
+    long long id, size;
+
+    long status = ParseElementHeader(pReader, pos, stop, id, size);
+
+    if (status < 0)  // error
+      return status;
+
+    if (id == libwebm::kMkvSamplingFrequency) {
+      status = UnserializeFloat(pReader, pos, size, rate);
+
+      if (status < 0)
+        return status;
+
+      if (rate <= 0)
+        return E_FILE_FORMAT_INVALID;
+    } else if (id == libwebm::kMkvChannels) {
+      channels = UnserializeUInt(pReader, pos, size);
+
+      if (channels <= 0)
+        return E_FILE_FORMAT_INVALID;
+    } else if (id == libwebm::kMkvBitDepth) {
+      bit_depth = UnserializeUInt(pReader, pos, size);
+
+      if (bit_depth <= 0)
+        return E_FILE_FORMAT_INVALID;
+    }
+
+    pos += size;  // consume payload
+    if (pos > stop)
+      return E_FILE_FORMAT_INVALID;
+  }
+
+  if (pos != stop)
+    return E_FILE_FORMAT_INVALID;
+
+  AudioTrack* const pTrack = new AudioTrack(pSegment, element_start, element_size);
+
+  const int status = info.Copy(pTrack->m_info);
+
+  if (status) {
+    delete pTrack;
+    return status;
+  }
+
+  pTrack->m_rate = rate;
+  pTrack->m_channels = channels;
+  pTrack->m_bitDepth = bit_depth;
+
+  pResult = pTrack;
+  return 0;  // success
+}
+
+double AudioTrack::GetSamplingRate() const { return m_rate; }
+
+long long AudioTrack::GetChannels() const { return m_channels; }
+
+long long AudioTrack::GetBitDepth() const { return m_bitDepth; }
+
+Tracks::Tracks(Segment* pSegment, long long start, long long size_,
+               long long element_start, long long element_size)
+    : m_pSegment(pSegment),
+      m_start(start),
+      m_size(size_),
+      m_element_start(element_start),
+      m_element_size(element_size),
+      m_trackEntries(NULL),
+      m_trackEntriesEnd(NULL) {}
+
+long Tracks::Parse() {
+  assert(m_trackEntries == NULL);
+  assert(m_trackEntriesEnd == NULL);
+
+  const long long stop = m_start + m_size;
+  IMkvReader* const pReader = m_pSegment->m_pReader;
+
+  int count = 0;
+  long long pos = m_start;
+
+  while (pos < stop) {
+    long long id, size;
+
+    const long status = ParseElementHeader(pReader, pos, stop, id, size);
+
+    if (status < 0)  // error
+      return status;
+
+    if (size == 0)  // weird
+      continue;
+
+    if (id == libwebm::kMkvTrackEntry)
+      ++count;
+
+    pos += size;  // consume payload
+    if (pos > stop)
+      return E_FILE_FORMAT_INVALID;
+  }
+
+  if (pos != stop)
+    return E_FILE_FORMAT_INVALID;
+
+  if (count <= 0)
+    return 0;  // success
+
+  m_trackEntries = new Track*[count];
+  m_trackEntriesEnd = m_trackEntries;
+
+  pos = m_start;
+
+  while (pos < stop) {
+    const long long element_start = pos;
+
+    long long id, payload_size;
+
+    const long status =
+        ParseElementHeader(pReader, pos, stop, id, payload_size);
+
+    if (status < 0)  // error
+      return status;
+
+    if (payload_size == 0)  // weird
+      continue;
+
+    const long long payload_stop = pos + payload_size;
+    assert(payload_stop <= stop);  // checked in ParseElement
+
+    const long long element_size = payload_stop - element_start;
+
+    if (id == libwebm::kMkvTrackEntry) {
+      Track*& pTrack = *m_trackEntriesEnd;
+      pTrack = NULL;
+
+      const long status = ParseTrackEntry(pos, payload_size, element_start,
+                                          element_size, pTrack);
+      if (status)
+        return status;
+
+      if (pTrack)
+        ++m_trackEntriesEnd;
+    }
+
+    pos = payload_stop;
+    if (pos > stop)
+      return E_FILE_FORMAT_INVALID;
+  }
+
+  if (pos != stop)
+    return E_FILE_FORMAT_INVALID;
+
+  return 0;  // success
+}
+
+unsigned long Tracks::GetTracksCount() const {
+  const ptrdiff_t result = m_trackEntriesEnd - m_trackEntries;
+  assert(result >= 0);
+
+  return static_cast<unsigned long>(result);
+}
+
+long Tracks::ParseTrackEntry(long long track_start, long long track_size,
+                             long long element_start, long long element_size,
+                             Track*& pResult) const {
+  if (pResult)
+    return -1;
+
+  IMkvReader* const pReader = m_pSegment->m_pReader;
+
+  long long pos = track_start;
+  const long long track_stop = track_start + track_size;
+
+  Track::Info info;
+
+  info.type = 0;
+  info.number = 0;
+  info.uid = 0;
+  info.defaultDuration = 0;
+
+  Track::Settings v;
+  v.start = -1;
+  v.size = -1;
+
+  Track::Settings a;
+  a.start = -1;
+  a.size = -1;
+
+  Track::Settings e;  // content_encodings_settings;
+  e.start = -1;
+  e.size = -1;
+
+  long long lacing = 1;  // default is true
+
+  while (pos < track_stop) {
+    long long id, size;
+
+    const long status = ParseElementHeader(pReader, pos, track_stop, id, size);
+
+    if (status < 0)  // error
+      return status;
+
+    if (size < 0)
+      return E_FILE_FORMAT_INVALID;
+
+    const long long start = pos;
+
+    if (id == libwebm::kMkvVideo) {
+      v.start = start;
+      v.size = size;
+    } else if (id == libwebm::kMkvAudio) {
+      a.start = start;
+      a.size = size;
+    } else if (id == libwebm::kMkvContentEncodings) {
+      e.start = start;
+      e.size = size;
+    } else if (id == libwebm::kMkvTrackUID) {
+      if (size > 8)
+        return E_FILE_FORMAT_INVALID;
+
+      info.uid = 0;
+
+      long long pos_ = start;
+      const long long pos_end = start + size;
+
+      while (pos_ != pos_end) {
+        unsigned char b;
+
+        const int status = pReader->Read(pos_, 1, &b);
+
+        if (status)
+          return status;
+
+        info.uid <<= 8;
+        info.uid |= b;
+
+        ++pos_;
+      }
+    } else if (id == libwebm::kMkvTrackNumber) {
+      const long long num = UnserializeUInt(pReader, pos, size);
+
+      if ((num <= 0) || (num > 127))
+        return E_FILE_FORMAT_INVALID;
+
+      info.number = static_cast<long>(num);
+    } else if (id == libwebm::kMkvTrackType) {
+      const long long type = UnserializeUInt(pReader, pos, size);
+
+      if ((type <= 0) || (type > 254))
+        return E_FILE_FORMAT_INVALID;
+
+      info.type = static_cast<long>(type);
+    } else if (id == libwebm::kMkvName) {
+      const long status =
+          UnserializeString(pReader, pos, size, info.nameAsUTF8);
+
+      if (status)
+        return status;
+    } else if (id == libwebm::kMkvLanguage) {
+      const long status = UnserializeString(pReader, pos, size, info.language);
+
+      if (status)
+        return status;
+    } else if (id == libwebm::kMkvDefaultDuration) {
+      const long long duration = UnserializeUInt(pReader, pos, size);
+
+      if (duration < 0)
+        return E_FILE_FORMAT_INVALID;
+
+      info.defaultDuration = static_cast<unsigned long long>(duration);
+    } else if (id == libwebm::kMkvCodecID) {
+      const long status = UnserializeString(pReader, pos, size, info.codecId);
+
+      if (status)
+        return status;
+    } else if (id == libwebm::kMkvFlagLacing) {
+      lacing = UnserializeUInt(pReader, pos, size);
+
+      if ((lacing < 0) || (lacing > 1))
+        return E_FILE_FORMAT_INVALID;
+    } else if (id == libwebm::kMkvCodecPrivate) {
+      delete[] info.codecPrivate;
+      info.codecPrivate = NULL;
+      info.codecPrivateSize = 0;
+
+      const size_t buflen = static_cast<size_t>(size);
+
+      if (buflen) {
+        unsigned char* buf = SafeArrayAlloc<unsigned char>(1, buflen);
+
+        if (buf == NULL)
+          return -1;
+
+        const int status = pReader->Read(pos, static_cast<long>(buflen), buf);
+
+        if (status) {
+          delete[] buf;
+          return status;
+        }
+
+        info.codecPrivate = buf;
+        info.codecPrivateSize = buflen;
+      }
+    } else if (id == libwebm::kMkvCodecName) {
+      const long status =
+          UnserializeString(pReader, pos, size, info.codecNameAsUTF8);
+
+      if (status)
+        return status;
+    } else if (id == libwebm::kMkvCodecDelay) {
+      info.codecDelay = UnserializeUInt(pReader, pos, size);
+    } else if (id == libwebm::kMkvSeekPreRoll) {
+      info.seekPreRoll = UnserializeUInt(pReader, pos, size);
+    }
+
+    pos += size;  // consume payload
+    if (pos > track_stop)
+      return E_FILE_FORMAT_INVALID;
+  }
+
+  if (pos != track_stop)
+    return E_FILE_FORMAT_INVALID;
+
+  if (info.number <= 0)  // not specified
+    return E_FILE_FORMAT_INVALID;
+
+  if (GetTrackByNumber(info.number))
+    return E_FILE_FORMAT_INVALID;
+
+  if (info.type <= 0)  // not specified
+    return E_FILE_FORMAT_INVALID;
+
+  info.lacing = (lacing > 0) ? true : false;
+
+  if (info.type == Track::kVideo) {
+    if (v.start < 0)
+      return E_FILE_FORMAT_INVALID;
+
+    if (a.start >= 0)
+      return E_FILE_FORMAT_INVALID;
+
+    info.settings = v;
+
+    VideoTrack* pTrack = NULL;
+
+    const long status = VideoTrack::Parse(m_pSegment, info, element_start,
+                                          element_size, pTrack);
+
+    if (status)
+      return status;
+
+    pResult = pTrack;
+    assert(pResult);
+
+    if (e.start >= 0)
+      pResult->ParseContentEncodingsEntry(e.start, e.size);
+  } else if (info.type == Track::kAudio) {
+    if (a.start < 0)
+      return E_FILE_FORMAT_INVALID;
+
+    if (v.start >= 0)
+      return E_FILE_FORMAT_INVALID;
+
+    info.settings = a;
+
+    AudioTrack* pTrack = NULL;
+
+    const long status = AudioTrack::Parse(m_pSegment, info, element_start,
+                                          element_size, pTrack);
+
+    if (status)
+      return status;
+
+    pResult = pTrack;
+    assert(pResult);
+
+    if (e.start >= 0)
+      pResult->ParseContentEncodingsEntry(e.start, e.size);
+  } else {
+    // neither video nor audio - probably metadata or subtitles
+
+    if (a.start >= 0)
+      return E_FILE_FORMAT_INVALID;
+
+    if (v.start >= 0)
+      return E_FILE_FORMAT_INVALID;
+
+    if (info.type == Track::kMetadata && e.start >= 0)
+      return E_FILE_FORMAT_INVALID;
+
+    info.settings.start = -1;
+    info.settings.size = 0;
+
+    Track* pTrack = NULL;
+
+    const long status =
+        Track::Create(m_pSegment, info, element_start, element_size, pTrack);
+
+    if (status)
+      return status;
+
+    pResult = pTrack;
+    assert(pResult);
+  }
+
+  return 0;  // success
+}
+
+Tracks::~Tracks() {
+  Track** i = m_trackEntries;
+  Track** const j = m_trackEntriesEnd;
+
+  while (i != j) {
+    Track* const pTrack = *i++;
+    delete pTrack;
+  }
+
+  delete[] m_trackEntries;
+}
+
+const Track* Tracks::GetTrackByNumber(long tn) const {
+  if (tn < 0)
+    return NULL;
+
+  Track** i = m_trackEntries;
+  Track** const j = m_trackEntriesEnd;
+
+  while (i != j) {
+    Track* const pTrack = *i++;
+
+    if (pTrack == NULL)
+      continue;
+
+    if (tn == pTrack->GetNumber())
+      return pTrack;
+  }
+
+  return NULL;  // not found
+}
+
+const Track* Tracks::GetTrackByIndex(unsigned long idx) const {
+  const ptrdiff_t count = m_trackEntriesEnd - m_trackEntries;
+
+  if (idx >= static_cast<unsigned long>(count))
+    return NULL;
+
+  return m_trackEntries[idx];
+}
+
+long Cluster::Load(long long& pos, long& len) const {
+  if (m_pSegment == NULL)
+    return E_PARSE_FAILED;
+
+  if (m_timecode >= 0)  // at least partially loaded
+    return 0;
+
+  if (m_pos != m_element_start || m_element_size >= 0)
+    return E_PARSE_FAILED;
+
+  IMkvReader* const pReader = m_pSegment->m_pReader;
+  long long total, avail;
+  const int status = pReader->Length(&total, &avail);
+
+  if (status < 0)  // error
+    return status;
+
+  if (total >= 0 && (avail > total || m_pos > total))
+    return E_FILE_FORMAT_INVALID;
+
+  pos = m_pos;
+
+  long long cluster_size = -1;
+
+  if ((pos + 1) > avail) {
+    len = 1;
+    return E_BUFFER_NOT_FULL;
+  }
+
+  long long result = GetUIntLength(pReader, pos, len);
+
+  if (result < 0)  // error or underflow
+    return static_cast<long>(result);
+
+  if (result > 0)
+    return E_BUFFER_NOT_FULL;
+
+  if ((pos + len) > avail)
+    return E_BUFFER_NOT_FULL;
+
+  const long long id_ = ReadID(pReader, pos, len);
+
+  if (id_ < 0)  // error
+    return static_cast<long>(id_);
+
+  if (id_ != libwebm::kMkvCluster)
+    return E_FILE_FORMAT_INVALID;
+
+  pos += len;  // consume id
+
+  // read cluster size
+
+  if ((pos + 1) > avail) {
+    len = 1;
+    return E_BUFFER_NOT_FULL;
+  }
+
+  result = GetUIntLength(pReader, pos, len);
+
+  if (result < 0)  // error
+    return static_cast<long>(result);
+
+  if (result > 0)
+    return E_BUFFER_NOT_FULL;
+
+  if ((pos + len) > avail)
+    return E_BUFFER_NOT_FULL;
+
+  const long long size = ReadUInt(pReader, pos, len);
+
+  if (size < 0)  // error
+    return static_cast<long>(cluster_size);
+
+  if (size == 0)
+    return E_FILE_FORMAT_INVALID;
+
+  pos += len;  // consume length of size of element
+
+  const long long unknown_size = (1LL << (7 * len)) - 1;
+
+  if (size != unknown_size)
+    cluster_size = size;
+
+  // pos points to start of payload
+  long long timecode = -1;
+  long long new_pos = -1;
+  bool bBlock = false;
+
+  long long cluster_stop = (cluster_size < 0) ? -1 : pos + cluster_size;
+
+  for (;;) {
+    if ((cluster_stop >= 0) && (pos >= cluster_stop))
+      break;
+
+    // Parse ID
+
+    if ((pos + 1) > avail) {
+      len = 1;
+      return E_BUFFER_NOT_FULL;
+    }
+
+    long long result = GetUIntLength(pReader, pos, len);
+
+    if (result < 0)  // error
+      return static_cast<long>(result);
+
+    if (result > 0)
+      return E_BUFFER_NOT_FULL;
+
+    if ((cluster_stop >= 0) && ((pos + len) > cluster_stop))
+      return E_FILE_FORMAT_INVALID;
+
+    if ((pos + len) > avail)
+      return E_BUFFER_NOT_FULL;
+
+    const long long id = ReadID(pReader, pos, len);
+
+    if (id < 0)  // error
+      return static_cast<long>(id);
+
+    if (id == 0)
+      return E_FILE_FORMAT_INVALID;
+
+    // This is the distinguished set of ID's we use to determine
+    // that we have exhausted the sub-element's inside the cluster
+    // whose ID we parsed earlier.
+
+    if (id == libwebm::kMkvCluster)
+      break;
+
+    if (id == libwebm::kMkvCues)
+      break;
+
+    pos += len;  // consume ID field
+
+    // Parse Size
+
+    if ((pos + 1) > avail) {
+      len = 1;
+      return E_BUFFER_NOT_FULL;
+    }
+
+    result = GetUIntLength(pReader, pos, len);
+
+    if (result < 0)  // error
+      return static_cast<long>(result);
+
+    if (result > 0)
+      return E_BUFFER_NOT_FULL;
+
+    if ((cluster_stop >= 0) && ((pos + len) > cluster_stop))
+      return E_FILE_FORMAT_INVALID;
+
+    if ((pos + len) > avail)
+      return E_BUFFER_NOT_FULL;
+
+    const long long size = ReadUInt(pReader, pos, len);
+
+    if (size < 0)  // error
+      return static_cast<long>(size);
+
+    const long long unknown_size = (1LL << (7 * len)) - 1;
+
+    if (size == unknown_size)
+      return E_FILE_FORMAT_INVALID;
+
+    pos += len;  // consume size field
+
+    if ((cluster_stop >= 0) && (pos > cluster_stop))
+      return E_FILE_FORMAT_INVALID;
+
+    // pos now points to start of payload
+
+    if (size == 0)
+      continue;
+
+    if ((cluster_stop >= 0) && ((pos + size) > cluster_stop))
+      return E_FILE_FORMAT_INVALID;
+
+    if (id == libwebm::kMkvTimecode) {
+      len = static_cast<long>(size);
+
+      if ((pos + size) > avail)
+        return E_BUFFER_NOT_FULL;
+
+      timecode = UnserializeUInt(pReader, pos, size);
+
+      if (timecode < 0)  // error (or underflow)
+        return static_cast<long>(timecode);
+
+      new_pos = pos + size;
+
+      if (bBlock)
+        break;
+    } else if (id == libwebm::kMkvBlockGroup) {
+      bBlock = true;
+      break;
+    } else if (id == libwebm::kMkvSimpleBlock) {
+      bBlock = true;
+      break;
+    }
+
+    pos += size;  // consume payload
+    if (cluster_stop >= 0 && pos > cluster_stop)
+      return E_FILE_FORMAT_INVALID;
+  }
+
+  if (cluster_stop >= 0 && pos > cluster_stop)
+    return E_FILE_FORMAT_INVALID;
+
+  if (timecode < 0)  // no timecode found
+    return E_FILE_FORMAT_INVALID;
+
+  if (!bBlock)
+    return E_FILE_FORMAT_INVALID;
+
+  m_pos = new_pos;  // designates position just beyond timecode payload
+  m_timecode = timecode;  // m_timecode >= 0 means we're partially loaded
+
+  if (cluster_size >= 0)
+    m_element_size = cluster_stop - m_element_start;
+
+  return 0;
+}
+
+long Cluster::Parse(long long& pos, long& len) const {
+  long status = Load(pos, len);
+
+  if (status < 0)
+    return status;
+
+  if (m_pos < m_element_start || m_timecode < 0)
+    return E_PARSE_FAILED;
+
+  const long long cluster_stop =
+      (m_element_size < 0) ? -1 : m_element_start + m_element_size;
+
+  if ((cluster_stop >= 0) && (m_pos >= cluster_stop))
+    return 1;  // nothing else to do
+
+  IMkvReader* const pReader = m_pSegment->m_pReader;
+
+  long long total, avail;
+
+  status = pReader->Length(&total, &avail);
+
+  if (status < 0)  // error
+    return status;
+
+  if (total >= 0 && avail > total)
+    return E_FILE_FORMAT_INVALID;
+
+  pos = m_pos;
+
+  for (;;) {
+    if ((cluster_stop >= 0) && (pos >= cluster_stop))
+      break;
+
+    if ((total >= 0) && (pos >= total)) {
+      if (m_element_size < 0)
+        m_element_size = pos - m_element_start;
+
+      break;
+    }
+
+    // Parse ID
+
+    if ((pos + 1) > avail) {
+      len = 1;
+      return E_BUFFER_NOT_FULL;
+    }
+
+    long long result = GetUIntLength(pReader, pos, len);
+
+    if (result < 0)  // error
+      return static_cast<long>(result);
+
+    if (result > 0)
+      return E_BUFFER_NOT_FULL;
+
+    if ((cluster_stop >= 0) && ((pos + len) > cluster_stop))
+      return E_FILE_FORMAT_INVALID;
+
+    if ((pos + len) > avail)
+      return E_BUFFER_NOT_FULL;
+
+    const long long id = ReadID(pReader, pos, len);
+
+    if (id < 0)
+      return E_FILE_FORMAT_INVALID;
+
+    // This is the distinguished set of ID's we use to determine
+    // that we have exhausted the sub-element's inside the cluster
+    // whose ID we parsed earlier.
+
+    if ((id == libwebm::kMkvCluster) || (id == libwebm::kMkvCues)) {
+      if (m_element_size < 0)
+        m_element_size = pos - m_element_start;
+
+      break;
+    }
+
+    pos += len;  // consume ID field
+
+    // Parse Size
+
+    if ((pos + 1) > avail) {
+      len = 1;
+      return E_BUFFER_NOT_FULL;
+    }
+
+    result = GetUIntLength(pReader, pos, len);
+
+    if (result < 0)  // error
+      return static_cast<long>(result);
+
+    if (result > 0)
+      return E_BUFFER_NOT_FULL;
+
+    if ((cluster_stop >= 0) && ((pos + len) > cluster_stop))
+      return E_FILE_FORMAT_INVALID;
+
+    if ((pos + len) > avail)
+      return E_BUFFER_NOT_FULL;
+
+    const long long size = ReadUInt(pReader, pos, len);
+
+    if (size < 0)  // error
+      return static_cast<long>(size);
+
+    const long long unknown_size = (1LL << (7 * len)) - 1;
+
+    if (size == unknown_size)
+      return E_FILE_FORMAT_INVALID;
+
+    pos += len;  // consume size field
+
+    if ((cluster_stop >= 0) && (pos > cluster_stop))
+      return E_FILE_FORMAT_INVALID;
+
+    // pos now points to start of payload
+
+    if (size == 0)
+      continue;
+
+    // const long long block_start = pos;
+    const long long block_stop = pos + size;
+
+    if (cluster_stop >= 0) {
+      if (block_stop > cluster_stop) {
+        if (id == libwebm::kMkvBlockGroup || id == libwebm::kMkvSimpleBlock) {
+          return E_FILE_FORMAT_INVALID;
+        }
+
+        pos = cluster_stop;
+        break;
+      }
+    } else if ((total >= 0) && (block_stop > total)) {
+      m_element_size = total - m_element_start;
+      pos = total;
+      break;
+    } else if (block_stop > avail) {
+      len = static_cast<long>(size);
+      return E_BUFFER_NOT_FULL;
+    }
+
+    Cluster* const this_ = const_cast<Cluster*>(this);
+
+    if (id == libwebm::kMkvBlockGroup)
+      return this_->ParseBlockGroup(size, pos, len);
+
+    if (id == libwebm::kMkvSimpleBlock)
+      return this_->ParseSimpleBlock(size, pos, len);
+
+    pos += size;  // consume payload
+    if (cluster_stop >= 0 && pos > cluster_stop)
+      return E_FILE_FORMAT_INVALID;
+  }
+
+  if (m_element_size < 1)
+    return E_FILE_FORMAT_INVALID;
+
+  m_pos = pos;
+  if (cluster_stop >= 0 && m_pos > cluster_stop)
+    return E_FILE_FORMAT_INVALID;
+
+  if (m_entries_count > 0) {
+    const long idx = m_entries_count - 1;
+
+    const BlockEntry* const pLast = m_entries[idx];
+    if (pLast == NULL)
+      return E_PARSE_FAILED;
+
+    const Block* const pBlock = pLast->GetBlock();
+    if (pBlock == NULL)
+      return E_PARSE_FAILED;
+
+    const long long start = pBlock->m_start;
+
+    if ((total >= 0) && (start > total))
+      return E_PARSE_FAILED;  // defend against trucated stream
+
+    const long long size = pBlock->m_size;
+
+    const long long stop = start + size;
+    if (cluster_stop >= 0 && stop > cluster_stop)
+      return E_FILE_FORMAT_INVALID;
+
+    if ((total >= 0) && (stop > total))
+      return E_PARSE_FAILED;  // defend against trucated stream
+  }
+
+  return 1;  // no more entries
+}
+
+long Cluster::ParseSimpleBlock(long long block_size, long long& pos,
+                               long& len) {
+  const long long block_start = pos;
+  const long long block_stop = pos + block_size;
+
+  IMkvReader* const pReader = m_pSegment->m_pReader;
+
+  long long total, avail;
+
+  long status = pReader->Length(&total, &avail);
+
+  if (status < 0)  // error
+    return status;
+
+  assert((total < 0) || (avail <= total));
+
+  // parse track number
+
+  if ((pos + 1) > avail) {
+    len = 1;
+    return E_BUFFER_NOT_FULL;
+  }
+
+  long long result = GetUIntLength(pReader, pos, len);
+
+  if (result < 0)  // error
+    return static_cast<long>(result);
+
+  if (result > 0)  // weird
+    return E_BUFFER_NOT_FULL;
+
+  if ((pos + len) > block_stop)
+    return E_FILE_FORMAT_INVALID;
+
+  if ((pos + len) > avail)
+    return E_BUFFER_NOT_FULL;
+
+  const long long track = ReadUInt(pReader, pos, len);
+
+  if (track < 0)  // error
+    return static_cast<long>(track);
+
+  if (track == 0)
+    return E_FILE_FORMAT_INVALID;
+
+  pos += len;  // consume track number
+
+  if ((pos + 2) > block_stop)
+    return E_FILE_FORMAT_INVALID;
+
+  if ((pos + 2) > avail) {
+    len = 2;
+    return E_BUFFER_NOT_FULL;
+  }
+
+  pos += 2;  // consume timecode
+
+  if ((pos + 1) > block_stop)
+    return E_FILE_FORMAT_INVALID;
+
+  if ((pos + 1) > avail) {
+    len = 1;
+    return E_BUFFER_NOT_FULL;
+  }
+
+  unsigned char flags;
+
+  status = pReader->Read(pos, 1, &flags);
+
+  if (status < 0) {  // error or underflow
+    len = 1;
+    return status;
+  }
+
+  ++pos;  // consume flags byte
+  assert(pos <= avail);
+
+  if (pos >= block_stop)
+    return E_FILE_FORMAT_INVALID;
+
+  const int lacing = int(flags & 0x06) >> 1;
+
+  if ((lacing != 0) && (block_stop > avail)) {
+    len = static_cast<long>(block_stop - pos);
+    return E_BUFFER_NOT_FULL;
+  }
+
+  status = CreateBlock(libwebm::kMkvSimpleBlock, block_start, block_size,
+                       0);  // DiscardPadding
+
+  if (status != 0)
+    return status;
+
+  m_pos = block_stop;
+
+  return 0;  // success
+}
+
+long Cluster::ParseBlockGroup(long long payload_size, long long& pos,
+                              long& len) {
+  const long long payload_start = pos;
+  const long long payload_stop = pos + payload_size;
+
+  IMkvReader* const pReader = m_pSegment->m_pReader;
+
+  long long total, avail;
+
+  long status = pReader->Length(&total, &avail);
+
+  if (status < 0)  // error
+    return status;
+
+  assert((total < 0) || (avail <= total));
+
+  if ((total >= 0) && (payload_stop > total))
+    return E_FILE_FORMAT_INVALID;
+
+  if (payload_stop > avail) {
+    len = static_cast<long>(payload_size);
+    return E_BUFFER_NOT_FULL;
+  }
+
+  long long discard_padding = 0;
+
+  while (pos < payload_stop) {
+    // parse sub-block element ID
+
+    if ((pos + 1) > avail) {
+      len = 1;
+      return E_BUFFER_NOT_FULL;
+    }
+
+    long long result = GetUIntLength(pReader, pos, len);
+
+    if (result < 0)  // error
+      return static_cast<long>(result);
+
+    if (result > 0)  // weird
+      return E_BUFFER_NOT_FULL;
+
+    if ((pos + len) > payload_stop)
+      return E_FILE_FORMAT_INVALID;
+
+    if ((pos + len) > avail)
+      return E_BUFFER_NOT_FULL;
+
+    const long long id = ReadID(pReader, pos, len);
+
+    if (id < 0)  // error
+      return static_cast<long>(id);
+
+    if (id == 0)  // not a valid ID
+      return E_FILE_FORMAT_INVALID;
+
+    pos += len;  // consume ID field
+
+    // Parse Size
+
+    if ((pos + 1) > avail) {
+      len = 1;
+      return E_BUFFER_NOT_FULL;
+    }
+
+    result = GetUIntLength(pReader, pos, len);
+
+    if (result < 0)  // error
+      return static_cast<long>(result);
+
+    if (result > 0)  // weird
+      return E_BUFFER_NOT_FULL;
+
+    if ((pos + len) > payload_stop)
+      return E_FILE_FORMAT_INVALID;
+
+    if ((pos + len) > avail)
+      return E_BUFFER_NOT_FULL;
+
+    const long long size = ReadUInt(pReader, pos, len);
+
+    if (size < 0)  // error
+      return static_cast<long>(size);
+
+    pos += len;  // consume size field
+
+    // pos now points to start of sub-block group payload
+
+    if (pos > payload_stop)
+      return E_FILE_FORMAT_INVALID;
+
+    if (size == 0)  // weird
+      continue;
+
+    const long long unknown_size = (1LL << (7 * len)) - 1;
+
+    if (size == unknown_size)
+      return E_FILE_FORMAT_INVALID;
+
+    if (id == libwebm::kMkvDiscardPadding) {
+      status = UnserializeInt(pReader, pos, size, discard_padding);
+
+      if (status < 0)  // error
+        return status;
+    }
+
+    if (id != libwebm::kMkvBlock) {
+      pos += size;  // consume sub-part of block group
+
+      if (pos > payload_stop)
+        return E_FILE_FORMAT_INVALID;
+
+      continue;
+    }
+
+    const long long block_stop = pos + size;
+
+    if (block_stop > payload_stop)
+      return E_FILE_FORMAT_INVALID;
+
+    // parse track number
+
+    if ((pos + 1) > avail) {
+      len = 1;
+      return E_BUFFER_NOT_FULL;
+    }
+
+    result = GetUIntLength(pReader, pos, len);
+
+    if (result < 0)  // error
+      return static_cast<long>(result);
+
+    if (result > 0)  // weird
+      return E_BUFFER_NOT_FULL;
+
+    if ((pos + len) > block_stop)
+      return E_FILE_FORMAT_INVALID;
+
+    if ((pos + len) > avail)
+      return E_BUFFER_NOT_FULL;
+
+    const long long track = ReadUInt(pReader, pos, len);
+
+    if (track < 0)  // error
+      return static_cast<long>(track);
+
+    if (track == 0)
+      return E_FILE_FORMAT_INVALID;
+
+    pos += len;  // consume track number
+
+    if ((pos + 2) > block_stop)
+      return E_FILE_FORMAT_INVALID;
+
+    if ((pos + 2) > avail) {
+      len = 2;
+      return E_BUFFER_NOT_FULL;
+    }
+
+    pos += 2;  // consume timecode
+
+    if ((pos + 1) > block_stop)
+      return E_FILE_FORMAT_INVALID;
+
+    if ((pos + 1) > avail) {
+      len = 1;
+      return E_BUFFER_NOT_FULL;
+    }
+
+    unsigned char flags;
+
+    status = pReader->Read(pos, 1, &flags);
+
+    if (status < 0) {  // error or underflow
+      len = 1;
+      return status;
+    }
+
+    ++pos;  // consume flags byte
+    assert(pos <= avail);
+
+    if (pos >= block_stop)
+      return E_FILE_FORMAT_INVALID;
+
+    const int lacing = int(flags & 0x06) >> 1;
+
+    if ((lacing != 0) && (block_stop > avail)) {
+      len = static_cast<long>(block_stop - pos);
+      return E_BUFFER_NOT_FULL;
+    }
+
+    pos = block_stop;  // consume block-part of block group
+    if (pos > payload_stop)
+      return E_FILE_FORMAT_INVALID;
+  }
+
+  if (pos != payload_stop)
+    return E_FILE_FORMAT_INVALID;
+
+  status = CreateBlock(libwebm::kMkvBlockGroup, payload_start, payload_size,
+                       discard_padding);
+  if (status != 0)
+    return status;
+
+  m_pos = payload_stop;
+
+  return 0;  // success
+}
+
+long Cluster::GetEntry(long index, const mkvparser::BlockEntry*& pEntry) const {
+  assert(m_pos >= m_element_start);
+
+  pEntry = NULL;
+
+  if (index < 0)
+    return -1;  // generic error
+
+  if (m_entries_count < 0)
+    return E_BUFFER_NOT_FULL;
+
+  assert(m_entries);
+  assert(m_entries_size > 0);
+  assert(m_entries_count <= m_entries_size);
+
+  if (index < m_entries_count) {
+    pEntry = m_entries[index];
+    assert(pEntry);
+
+    return 1;  // found entry
+  }
+
+  if (m_element_size < 0)  // we don't know cluster end yet
+    return E_BUFFER_NOT_FULL;  // underflow
+
+  const long long element_stop = m_element_start + m_element_size;
+
+  if (m_pos >= element_stop)
+    return 0;  // nothing left to parse
+
+  return E_BUFFER_NOT_FULL;  // underflow, since more remains to be parsed
+}
+
+Cluster* Cluster::Create(Segment* pSegment, long idx, long long off) {
+  if (!pSegment || off < 0)
+    return NULL;
+
+  const long long element_start = pSegment->m_start + off;
+
+  return new Cluster(pSegment, idx, element_start);
+}
+
+Cluster::Cluster()
+    : m_pSegment(NULL),
+      m_element_start(0),
+      m_index(0),
+      m_pos(0),
+      m_element_size(0),
+      m_timecode(0),
+      m_entries(NULL),
+      m_entries_size(0),
+      m_entries_count(0)  // means "no entries"
+{}
+
+Cluster::Cluster(Segment* pSegment, long idx, long long element_start
+                 /* long long element_size */)
+    : m_pSegment(pSegment),
+      m_element_start(element_start),
+      m_index(idx),
+      m_pos(element_start),
+      m_element_size(-1 /* element_size */),
+      m_timecode(-1),
+      m_entries(NULL),
+      m_entries_size(0),
+      m_entries_count(-1)  // means "has not been parsed yet"
+{}
+
+Cluster::~Cluster() {
+  if (m_entries_count <= 0)
+    return;
+
+  BlockEntry** i = m_entries;
+  BlockEntry** const j = m_entries + m_entries_count;
+
+  while (i != j) {
+    BlockEntry* p = *i++;
+    assert(p);
+
+    delete p;
+  }
+
+  delete[] m_entries;
+}
+
+bool Cluster::EOS() const { return (m_pSegment == NULL); }
+
+long Cluster::GetIndex() const { return m_index; }
+
+long long Cluster::GetPosition() const {
+  const long long pos = m_element_start - m_pSegment->m_start;
+  assert(pos >= 0);
+
+  return pos;
+}
+
+long long Cluster::GetElementSize() const { return m_element_size; }
+
+long Cluster::HasBlockEntries(
+    const Segment* pSegment,
+    long long off,  // relative to start of segment payload
+    long long& pos, long& len) {
+  assert(pSegment);
+  assert(off >= 0);  // relative to segment
+
+  IMkvReader* const pReader = pSegment->m_pReader;
+
+  long long total, avail;
+
+  long status = pReader->Length(&total, &avail);
+
+  if (status < 0)  // error
+    return status;
+
+  assert((total < 0) || (avail <= total));
+
+  pos = pSegment->m_start + off;  // absolute
+
+  if ((total >= 0) && (pos >= total))
+    return 0;  // we don't even have a complete cluster
+
+  const long long segment_stop =
+      (pSegment->m_size < 0) ? -1 : pSegment->m_start + pSegment->m_size;
+
+  long long cluster_stop = -1;  // interpreted later to mean "unknown size"
+
+  {
+    if ((pos + 1) > avail) {
+      len = 1;
+      return E_BUFFER_NOT_FULL;
+    }
+
+    long long result = GetUIntLength(pReader, pos, len);
+
+    if (result < 0)  // error
+      return static_cast<long>(result);
+
+    if (result > 0)  // need more data
+      return E_BUFFER_NOT_FULL;
+
+    if ((segment_stop >= 0) && ((pos + len) > segment_stop))
+      return E_FILE_FORMAT_INVALID;
+
+    if ((total >= 0) && ((pos + len) > total))
+      return 0;
+
+    if ((pos + len) > avail)
+      return E_BUFFER_NOT_FULL;
+
+    const long long id = ReadID(pReader, pos, len);
+
+    if (id < 0)  // error
+      return static_cast<long>(id);
+
+    if (id != libwebm::kMkvCluster)
+      return E_PARSE_FAILED;
+
+    pos += len;  // consume Cluster ID field
+
+    // read size field
+
+    if ((pos + 1) > avail) {
+      len = 1;
+      return E_BUFFER_NOT_FULL;
+    }
+
+    result = GetUIntLength(pReader, pos, len);
+
+    if (result < 0)  // error
+      return static_cast<long>(result);
+
+    if (result > 0)  // weird
+      return E_BUFFER_NOT_FULL;
+
+    if ((segment_stop >= 0) && ((pos + len) > segment_stop))
+      return E_FILE_FORMAT_INVALID;
+
+    if ((total >= 0) && ((pos + len) > total))
+      return 0;
+
+    if ((pos + len) > avail)
+      return E_BUFFER_NOT_FULL;
+
+    const long long size = ReadUInt(pReader, pos, len);
+
+    if (size < 0)  // error
+      return static_cast<long>(size);
+
+    if (size == 0)
+      return 0;  // cluster does not have entries
+
+    pos += len;  // consume size field
+
+    // pos now points to start of payload
+
+    const long long unknown_size = (1LL << (7 * len)) - 1;
+
+    if (size != unknown_size) {
+      cluster_stop = pos + size;
+      assert(cluster_stop >= 0);
+
+      if ((segment_stop >= 0) && (cluster_stop > segment_stop))
+        return E_FILE_FORMAT_INVALID;
+
+      if ((total >= 0) && (cluster_stop > total))
+        // return E_FILE_FORMAT_INVALID;  //too conservative
+        return 0;  // cluster does not have any entries
+    }
+  }
+
+  for (;;) {
+    if ((cluster_stop >= 0) && (pos >= cluster_stop))
+      return 0;  // no entries detected
+
+    if ((pos + 1) > avail) {
+      len = 1;
+      return E_BUFFER_NOT_FULL;
+    }
+
+    long long result = GetUIntLength(pReader, pos, len);
+
+    if (result < 0)  // error
+      return static_cast<long>(result);
+
+    if (result > 0)  // need more data
+      return E_BUFFER_NOT_FULL;
+
+    if ((cluster_stop >= 0) && ((pos + len) > cluster_stop))
+      return E_FILE_FORMAT_INVALID;
+
+    if ((pos + len) > avail)
+      return E_BUFFER_NOT_FULL;
+
+    const long long id = ReadID(pReader, pos, len);
+
+    if (id < 0)  // error
+      return static_cast<long>(id);
+
+    // This is the distinguished set of ID's we use to determine
+    // that we have exhausted the sub-element's inside the cluster
+    // whose ID we parsed earlier.
+
+    if (id == libwebm::kMkvCluster)
+      return 0;  // no entries found
+
+    if (id == libwebm::kMkvCues)
+      return 0;  // no entries found
+
+    pos += len;  // consume id field
+
+    if ((cluster_stop >= 0) && (pos >= cluster_stop))
+      return E_FILE_FORMAT_INVALID;
+
+    // read size field
+
+    if ((pos + 1) > avail) {
+      len = 1;
+      return E_BUFFER_NOT_FULL;
+    }
+
+    result = GetUIntLength(pReader, pos, len);
+
+    if (result < 0)  // error
+      return static_cast<long>(result);
+
+    if (result > 0)  // underflow
+      return E_BUFFER_NOT_FULL;
+
+    if ((cluster_stop >= 0) && ((pos + len) > cluster_stop))
+      return E_FILE_FORMAT_INVALID;
+
+    if ((pos + len) > avail)
+      return E_BUFFER_NOT_FULL;
+
+    const long long size = ReadUInt(pReader, pos, len);
+
+    if (size < 0)  // error
+      return static_cast<long>(size);
+
+    pos += len;  // consume size field
+
+    // pos now points to start of payload
+
+    if ((cluster_stop >= 0) && (pos > cluster_stop))
+      return E_FILE_FORMAT_INVALID;
+
+    if (size == 0)  // weird
+      continue;
+
+    const long long unknown_size = (1LL << (7 * len)) - 1;
+
+    if (size == unknown_size)
+      return E_FILE_FORMAT_INVALID;  // not supported inside cluster
+
+    if ((cluster_stop >= 0) && ((pos + size) > cluster_stop))
+      return E_FILE_FORMAT_INVALID;
+
+    if (id == libwebm::kMkvBlockGroup)
+      return 1;  // have at least one entry
+
+    if (id == libwebm::kMkvSimpleBlock)
+      return 1;  // have at least one entry
+
+    pos += size;  // consume payload
+    if (cluster_stop >= 0 && pos > cluster_stop)
+      return E_FILE_FORMAT_INVALID;
+  }
+}
+
+long long Cluster::GetTimeCode() const {
+  long long pos;
+  long len;
+
+  const long status = Load(pos, len);
+
+  if (status < 0)  // error
+    return status;
+
+  return m_timecode;
+}
+
+long long Cluster::GetTime() const {
+  const long long tc = GetTimeCode();
+
+  if (tc < 0)
+    return tc;
+
+  const SegmentInfo* const pInfo = m_pSegment->GetInfo();
+  assert(pInfo);
+
+  const long long scale = pInfo->GetTimeCodeScale();
+  assert(scale >= 1);
+
+  const long long t = m_timecode * scale;
+
+  return t;
+}
+
+long long Cluster::GetFirstTime() const {
+  const BlockEntry* pEntry;
+
+  const long status = GetFirst(pEntry);
+
+  if (status < 0)  // error
+    return status;
+
+  if (pEntry == NULL)  // empty cluster
+    return GetTime();
+
+  const Block* const pBlock = pEntry->GetBlock();
+  assert(pBlock);
+
+  return pBlock->GetTime(this);
+}
+
+long long Cluster::GetLastTime() const {
+  const BlockEntry* pEntry;
+
+  const long status = GetLast(pEntry);
+
+  if (status < 0)  // error
+    return status;
+
+  if (pEntry == NULL)  // empty cluster
+    return GetTime();
+
+  const Block* const pBlock = pEntry->GetBlock();
+  assert(pBlock);
+
+  return pBlock->GetTime(this);
+}
+
+long Cluster::CreateBlock(long long id,
+                          long long pos,  // absolute pos of payload
+                          long long size, long long discard_padding) {
+  if (id != libwebm::kMkvBlockGroup && id != libwebm::kMkvSimpleBlock)
+    return E_PARSE_FAILED;
+
+  if (m_entries_count < 0) {  // haven't parsed anything yet
+    assert(m_entries == NULL);
+    assert(m_entries_size == 0);
+
+    m_entries_size = 1024;
+    m_entries = new BlockEntry*[m_entries_size];
+
+    m_entries_count = 0;
+  } else {
+    assert(m_entries);
+    assert(m_entries_size > 0);
+    assert(m_entries_count <= m_entries_size);
+
+    if (m_entries_count >= m_entries_size) {
+      const long entries_size = 2 * m_entries_size;
+
+      BlockEntry** const entries = new BlockEntry*[entries_size];
+
+      BlockEntry** src = m_entries;
+      BlockEntry** const src_end = src + m_entries_count;
+
+      BlockEntry** dst = entries;
+
+      while (src != src_end)
+        *dst++ = *src++;
+
+      delete[] m_entries;
+
+      m_entries = entries;
+      m_entries_size = entries_size;
+    }
+  }
+
+  if (id == libwebm::kMkvBlockGroup)
+    return CreateBlockGroup(pos, size, discard_padding);
+  else
+    return CreateSimpleBlock(pos, size);
+}
+
+long Cluster::CreateBlockGroup(long long start_offset, long long size,
+                               long long discard_padding) {
+  assert(m_entries);
+  assert(m_entries_size > 0);
+  assert(m_entries_count >= 0);
+  assert(m_entries_count < m_entries_size);
+
+  IMkvReader* const pReader = m_pSegment->m_pReader;
+
+  long long pos = start_offset;
+  const long long stop = start_offset + size;
+
+  // For WebM files, there is a bias towards previous reference times
+  //(in order to support alt-ref frames, which refer back to the previous
+  // keyframe).  Normally a 0 value is not possible, but here we tenatively
+  // allow 0 as the value of a reference frame, with the interpretation
+  // that this is a "previous" reference time.
+
+  long long prev = 1;  // nonce
+  long long next = 0;  // nonce
+  long long duration = -1;  // really, this is unsigned
+
+  long long bpos = -1;
+  long long bsize = -1;
+
+  while (pos < stop) {
+    long len;
+    const long long id = ReadID(pReader, pos, len);
+    if (id < 0 || (pos + len) > stop)
+      return E_FILE_FORMAT_INVALID;
+
+    pos += len;  // consume ID
+
+    const long long size = ReadUInt(pReader, pos, len);
+    assert(size >= 0);  // TODO
+    assert((pos + len) <= stop);
+
+    pos += len;  // consume size
+
+    if (id == libwebm::kMkvBlock) {
+      if (bpos < 0) {  // Block ID
+        bpos = pos;
+        bsize = size;
+      }
+    } else if (id == libwebm::kMkvBlockDuration) {
+      if (size > 8)
+        return E_FILE_FORMAT_INVALID;
+
+      duration = UnserializeUInt(pReader, pos, size);
+
+      if (duration < 0)
+        return E_FILE_FORMAT_INVALID;
+    } else if (id == libwebm::kMkvReferenceBlock) {
+      if (size > 8 || size <= 0)
+        return E_FILE_FORMAT_INVALID;
+      const long size_ = static_cast<long>(size);
+
+      long long time;
+
+      long status = UnserializeInt(pReader, pos, size_, time);
+      assert(status == 0);
+      if (status != 0)
+        return -1;
+
+      if (time <= 0)  // see note above
+        prev = time;
+      else
+        next = time;
+    }
+
+    pos += size;  // consume payload
+    if (pos > stop)
+      return E_FILE_FORMAT_INVALID;
+  }
+  if (bpos < 0)
+    return E_FILE_FORMAT_INVALID;
+
+  if (pos != stop)
+    return E_FILE_FORMAT_INVALID;
+  assert(bsize >= 0);
+
+  const long idx = m_entries_count;
+
+  BlockEntry** const ppEntry = m_entries + idx;
+  BlockEntry*& pEntry = *ppEntry;
+
+  pEntry = new BlockGroup(this, idx, bpos, bsize, prev, next, duration, discard_padding);
+
+  BlockGroup* const p = static_cast<BlockGroup*>(pEntry);
+
+  const long status = p->Parse();
+
+  if (status == 0) {  // success
+    ++m_entries_count;
+    return 0;
+  }
+
+  delete pEntry;
+  pEntry = 0;
+
+  return status;
+}
+
+long Cluster::CreateSimpleBlock(long long st, long long sz) {
+  assert(m_entries);
+  assert(m_entries_size > 0);
+  assert(m_entries_count >= 0);
+  assert(m_entries_count < m_entries_size);
+
+  const long idx = m_entries_count;
+
+  BlockEntry** const ppEntry = m_entries + idx;
+  BlockEntry*& pEntry = *ppEntry;
+
+  pEntry = new SimpleBlock(this, idx, st, sz);
+
+  SimpleBlock* const p = static_cast<SimpleBlock*>(pEntry);
+
+  const long status = p->Parse();
+
+  if (status == 0) {
+    ++m_entries_count;
+    return 0;
+  }
+
+  delete pEntry;
+  pEntry = 0;
+
+  return status;
+}
+
+long Cluster::GetFirst(const BlockEntry*& pFirst) const {
+  if (m_entries_count <= 0) {
+    long long pos;
+    long len;
+
+    const long status = Parse(pos, len);
+
+    if (status < 0) {  // error
+      pFirst = NULL;
+      return status;
+    }
+
+    if (m_entries_count <= 0) {  // empty cluster
+      pFirst = NULL;
+      return 0;
+    }
+  }
+
+  assert(m_entries);
+
+  pFirst = m_entries[0];
+  assert(pFirst);
+
+  return 0;  // success
+}
+
+long Cluster::GetLast(const BlockEntry*& pLast) const {
+  for (;;) {
+    long long pos;
+    long len;
+
+    const long status = Parse(pos, len);
+
+    if (status < 0) {  // error
+      pLast = NULL;
+      return status;
+    }
+
+    if (status > 0)  // no new block
+      break;
+  }
+
+  if (m_entries_count <= 0) {
+    pLast = NULL;
+    return 0;
+  }
+
+  assert(m_entries);
+
+  const long idx = m_entries_count - 1;
+
+  pLast = m_entries[idx];
+  assert(pLast);
+
+  return 0;
+}
+
+long Cluster::GetNext(const BlockEntry* pCurr, const BlockEntry*& pNext) const {
+  assert(pCurr);
+  assert(m_entries);
+  assert(m_entries_count > 0);
+
+  size_t idx = pCurr->GetIndex();
+  assert(idx < size_t(m_entries_count));
+  assert(m_entries[idx] == pCurr);
+
+  ++idx;
+
+  if (idx >= size_t(m_entries_count)) {
+    long long pos;
+    long len;
+
+    const long status = Parse(pos, len);
+
+    if (status < 0) {  // error
+      pNext = NULL;
+      return status;
+    }
+
+    if (status > 0) {
+      pNext = NULL;
+      return 0;
+    }
+
+    assert(m_entries);
+    assert(m_entries_count > 0);
+    assert(idx < size_t(m_entries_count));
+  }
+
+  pNext = m_entries[idx];
+  assert(pNext);
+
+  return 0;
+}
+
+long Cluster::GetEntryCount() const { return m_entries_count; }
+
+const BlockEntry* Cluster::GetEntry(const Track* pTrack,
+                                    long long time_ns) const {
+  assert(pTrack);
+
+  if (m_pSegment == NULL)  // this is the special EOS cluster
+    return pTrack->GetEOS();
+
+  const BlockEntry* pResult = pTrack->GetEOS();
+
+  long index = 0;
+
+  for (;;) {
+    if (index >= m_entries_count) {
+      long long pos;
+      long len;
+
+      const long status = Parse(pos, len);
+      assert(status >= 0);
+
+      if (status > 0)  // completely parsed, and no more entries
+        return pResult;
+
+      if (status < 0)  // should never happen
+        return 0;
+
+      assert(m_entries);
+      assert(index < m_entries_count);
+    }
+
+    const BlockEntry* const pEntry = m_entries[index];
+    assert(pEntry);
+    assert(!pEntry->EOS());
+
+    const Block* const pBlock = pEntry->GetBlock();
+    assert(pBlock);
+
+    if (pBlock->GetTrackNumber() != pTrack->GetNumber()) {
+      ++index;
+      continue;
+    }
+
+    if (pTrack->VetEntry(pEntry)) {
+      if (time_ns < 0)  // just want first candidate block
+        return pEntry;
+
+      const long long ns = pBlock->GetTime(this);
+
+      if (ns > time_ns)
+        return pResult;
+
+      pResult = pEntry;  // have a candidate
+    } else if (time_ns >= 0) {
+      const long long ns = pBlock->GetTime(this);
+
+      if (ns > time_ns)
+        return pResult;
+    }
+
+    ++index;
+  }
+}
+
+const BlockEntry* Cluster::GetEntry(const CuePoint& cp,
+                                    const CuePoint::TrackPosition& tp) const {
+  assert(m_pSegment);
+  const long long tc = cp.GetTimeCode();
+
+  if (tp.m_block > 0) {
+    const long block = static_cast<long>(tp.m_block);
+    const long index = block - 1;
+
+    while (index >= m_entries_count) {
+      long long pos;
+      long len;
+
+      const long status = Parse(pos, len);
+
+      if (status < 0)  // TODO: can this happen?
+        return NULL;
+
+      if (status > 0)  // nothing remains to be parsed
+        return NULL;
+    }
+
+    const BlockEntry* const pEntry = m_entries[index];
+    assert(pEntry);
+    assert(!pEntry->EOS());
+
+    const Block* const pBlock = pEntry->GetBlock();
+    assert(pBlock);
+
+    if ((pBlock->GetTrackNumber() == tp.m_track) &&
+        (pBlock->GetTimeCode(this) == tc)) {
+      return pEntry;
+    }
+  }
+
+  long index = 0;
+
+  for (;;) {
+    if (index >= m_entries_count) {
+      long long pos;
+      long len;
+
+      const long status = Parse(pos, len);
+
+      if (status < 0)  // TODO: can this happen?
+        return NULL;
+
+      if (status > 0)  // nothing remains to be parsed
+        return NULL;
+
+      assert(m_entries);
+      assert(index < m_entries_count);
+    }
+
+    const BlockEntry* const pEntry = m_entries[index];
+    assert(pEntry);
+    assert(!pEntry->EOS());
+
+    const Block* const pBlock = pEntry->GetBlock();
+    assert(pBlock);
+
+    if (pBlock->GetTrackNumber() != tp.m_track) {
+      ++index;
+      continue;
+    }
+
+    const long long tc_ = pBlock->GetTimeCode(this);
+
+    if (tc_ < tc) {
+      ++index;
+      continue;
+    }
+
+    if (tc_ > tc)
+      return NULL;
+
+    const Tracks* const pTracks = m_pSegment->GetTracks();
+    assert(pTracks);
+
+    const long tn = static_cast<long>(tp.m_track);
+    const Track* const pTrack = pTracks->GetTrackByNumber(tn);
+
+    if (pTrack == NULL)
+      return NULL;
+
+    const long long type = pTrack->GetType();
+
+    if (type == 2)  // audio
+      return pEntry;
+
+    if (type != 1)  // not video
+      return NULL;
+
+    if (!pBlock->IsKey())
+      return NULL;
+
+    return pEntry;
+  }
+}
+
+BlockEntry::BlockEntry(Cluster* p, long idx) : m_pCluster(p), m_index(idx) {}
+BlockEntry::~BlockEntry() {}
+const Cluster* BlockEntry::GetCluster() const { return m_pCluster; }
+long BlockEntry::GetIndex() const { return m_index; }
+
+SimpleBlock::SimpleBlock(Cluster* pCluster, long idx, long long start,
+                         long long size)
+    : BlockEntry(pCluster, idx), m_block(start, size, 0) {}
+
+long SimpleBlock::Parse() { return m_block.Parse(m_pCluster); }
+BlockEntry::Kind SimpleBlock::GetKind() const { return kBlockSimple; }
+const Block* SimpleBlock::GetBlock() const { return &m_block; }
+
+BlockGroup::BlockGroup(Cluster* pCluster, long idx, long long block_start,
+                       long long block_size, long long prev, long long next,
+                       long long duration, long long discard_padding)
+    : BlockEntry(pCluster, idx),
+      m_block(block_start, block_size, discard_padding),
+      m_prev(prev),
+      m_next(next),
+      m_duration(duration) {}
+
+long BlockGroup::Parse() {
+  const long status = m_block.Parse(m_pCluster);
+
+  if (status)
+    return status;
+
+  m_block.SetKey((m_prev > 0) && (m_next <= 0));
+
+  return 0;
+}
+
+BlockEntry::Kind BlockGroup::GetKind() const { return kBlockGroup; }
+const Block* BlockGroup::GetBlock() const { return &m_block; }
+long long BlockGroup::GetPrevTimeCode() const { return m_prev; }
+long long BlockGroup::GetNextTimeCode() const { return m_next; }
+long long BlockGroup::GetDurationTimeCode() const { return m_duration; }
+
+Block::Block(long long start, long long size_, long long discard_padding)
+    : m_start(start),
+      m_size(size_),
+      m_track(0),
+      m_timecode(-1),
+      m_flags(0),
+      m_frames(NULL),
+      m_frame_count(-1),
+      m_discard_padding(discard_padding) {}
+
+Block::~Block() { delete[] m_frames; }
+
+long Block::Parse(const Cluster* pCluster) {
+  if (pCluster == NULL)
+    return -1;
+
+  if (pCluster->m_pSegment == NULL)
+    return -1;
+
+  assert(m_start >= 0);
+  assert(m_size >= 0);
+  assert(m_track <= 0);
+  assert(m_frames == NULL);
+  assert(m_frame_count <= 0);
+
+  long long pos = m_start;
+  const long long stop = m_start + m_size;
+
+  long len;
+
+  IMkvReader* const pReader = pCluster->m_pSegment->m_pReader;
+
+  m_track = ReadUInt(pReader, pos, len);
+
+  if (m_track <= 0)
+    return E_FILE_FORMAT_INVALID;
+
+  if ((pos + len) > stop)
+    return E_FILE_FORMAT_INVALID;
+
+  pos += len;  // consume track number
+
+  if ((stop - pos) < 2)
+    return E_FILE_FORMAT_INVALID;
+
+  long status;
+  long long value;
+
+  status = UnserializeInt(pReader, pos, 2, value);
+
+  if (status)
+    return E_FILE_FORMAT_INVALID;
+
+  if (value < SHRT_MIN)
+    return E_FILE_FORMAT_INVALID;
+
+  if (value > SHRT_MAX)
+    return E_FILE_FORMAT_INVALID;
+
+  m_timecode = static_cast<short>(value);
+
+  pos += 2;
+
+  if ((stop - pos) <= 0)
+    return E_FILE_FORMAT_INVALID;
+
+  status = pReader->Read(pos, 1, &m_flags);
+
+  if (status)
+    return E_FILE_FORMAT_INVALID;
+
+  const int lacing = int(m_flags & 0x06) >> 1;
+
+  ++pos;  // consume flags byte
+
+  if (lacing == 0) {  // no lacing
+    if (pos > stop)
+      return E_FILE_FORMAT_INVALID;
+
+    m_frame_count = 1;
+    m_frames = new Frame[m_frame_count];
+
+    Frame& f = m_frames[0];
+    f.pos = pos;
+
+    const long long frame_size = stop - pos;
+
+    if (frame_size > LONG_MAX || frame_size <= 0)
+      return E_FILE_FORMAT_INVALID;
+
+    f.len = static_cast<long>(frame_size);
+
+    return 0;  // success
+  }
+
+  if (pos >= stop)
+    return E_FILE_FORMAT_INVALID;
+
+  unsigned char biased_count;
+
+  status = pReader->Read(pos, 1, &biased_count);
+
+  if (status)
+    return E_FILE_FORMAT_INVALID;
+
+  ++pos;  // consume frame count
+  if (pos > stop)
+    return E_FILE_FORMAT_INVALID;
+
+  m_frame_count = int(biased_count) + 1;
+
+  m_frames = new Frame[m_frame_count];
+
+  if (!m_frames)
+    return E_FILE_FORMAT_INVALID;
+
+  if (lacing == 1) {  // Xiph
+    Frame* pf = m_frames;
+    Frame* const pf_end = pf + m_frame_count;
+
+    long long size = 0;
+    int frame_count = m_frame_count;
+
+    while (frame_count > 1) {
+      long frame_size = 0;
+
+      for (;;) {
+        unsigned char val;
+
+        if (pos >= stop)
+          return E_FILE_FORMAT_INVALID;
+
+        status = pReader->Read(pos, 1, &val);
+
+        if (status)
+          return E_FILE_FORMAT_INVALID;
+
+        ++pos;  // consume xiph size byte
+
+        frame_size += val;
+
+        if (val < 255)
+          break;
+      }
+
+      Frame& f = *pf++;
+      assert(pf < pf_end);
+      if (pf >= pf_end)
+        return E_FILE_FORMAT_INVALID;
+
+      f.pos = 0;  // patch later
+
+      if (frame_size <= 0)
+        return E_FILE_FORMAT_INVALID;
+
+      f.len = frame_size;
+      size += frame_size;  // contribution of this frame
+
+      --frame_count;
+    }
+
+    if (pf >= pf_end || pos > stop)
+      return E_FILE_FORMAT_INVALID;
+
+    {
+      Frame& f = *pf++;
+
+      if (pf != pf_end)
+        return E_FILE_FORMAT_INVALID;
+
+      f.pos = 0;  // patch later
+
+      const long long total_size = stop - pos;
+
+      if (total_size < size)
+        return E_FILE_FORMAT_INVALID;
+
+      const long long frame_size = total_size - size;
+
+      if (frame_size > LONG_MAX || frame_size <= 0)
+        return E_FILE_FORMAT_INVALID;
+
+      f.len = static_cast<long>(frame_size);
+    }
+
+    pf = m_frames;
+    while (pf != pf_end) {
+      Frame& f = *pf++;
+      assert((pos + f.len) <= stop);
+
+      if ((pos + f.len) > stop)
+        return E_FILE_FORMAT_INVALID;
+
+      f.pos = pos;
+      pos += f.len;
+    }
+
+    assert(pos == stop);
+    if (pos != stop)
+      return E_FILE_FORMAT_INVALID;
+
+  } else if (lacing == 2) {  // fixed-size lacing
+    if (pos >= stop)
+      return E_FILE_FORMAT_INVALID;
+
+    const long long total_size = stop - pos;
+
+    if ((total_size % m_frame_count) != 0)
+      return E_FILE_FORMAT_INVALID;
+
+    const long long frame_size = total_size / m_frame_count;
+
+    if (frame_size > LONG_MAX || frame_size <= 0)
+      return E_FILE_FORMAT_INVALID;
+
+    Frame* pf = m_frames;
+    Frame* const pf_end = pf + m_frame_count;
+
+    while (pf != pf_end) {
+      assert((pos + frame_size) <= stop);
+      if ((pos + frame_size) > stop)
+        return E_FILE_FORMAT_INVALID;
+
+      Frame& f = *pf++;
+
+      f.pos = pos;
+      f.len = static_cast<long>(frame_size);
+
+      pos += frame_size;
+    }
+
+    assert(pos == stop);
+    if (pos != stop)
+      return E_FILE_FORMAT_INVALID;
+
+  } else {
+    assert(lacing == 3);  // EBML lacing
+
+    if (pos >= stop)
+      return E_FILE_FORMAT_INVALID;
+
+    long long size = 0;
+    int frame_count = m_frame_count;
+
+    long long frame_size = ReadUInt(pReader, pos, len);
+
+    if (frame_size <= 0)
+      return E_FILE_FORMAT_INVALID;
+
+    if (frame_size > LONG_MAX)
+      return E_FILE_FORMAT_INVALID;
+
+    if ((pos + len) > stop)
+      return E_FILE_FORMAT_INVALID;
+
+    pos += len;  // consume length of size of first frame
+
+    if ((pos + frame_size) > stop)
+      return E_FILE_FORMAT_INVALID;
+
+    Frame* pf = m_frames;
+    Frame* const pf_end = pf + m_frame_count;
+
+    {
+      Frame& curr = *pf;
+
+      curr.pos = 0;  // patch later
+
+      curr.len = static_cast<long>(frame_size);
+      size += curr.len;  // contribution of this frame
+    }
+
+    --frame_count;
+
+    while (frame_count > 1) {
+      if (pos >= stop)
+        return E_FILE_FORMAT_INVALID;
+
+      assert(pf < pf_end);
+      if (pf >= pf_end)
+        return E_FILE_FORMAT_INVALID;
+
+      const Frame& prev = *pf++;
+      assert(prev.len == frame_size);
+      if (prev.len != frame_size)
+        return E_FILE_FORMAT_INVALID;
+
+      assert(pf < pf_end);
+      if (pf >= pf_end)
+        return E_FILE_FORMAT_INVALID;
+
+      Frame& curr = *pf;
+
+      curr.pos = 0;  // patch later
+
+      const long long delta_size_ = ReadUInt(pReader, pos, len);
+
+      if (delta_size_ < 0)
+        return E_FILE_FORMAT_INVALID;
+
+      if ((pos + len) > stop)
+        return E_FILE_FORMAT_INVALID;
+
+      pos += len;  // consume length of (delta) size
+      if (pos > stop)
+        return E_FILE_FORMAT_INVALID;
+
+      const long exp = 7 * len - 1;
+      const long long bias = (1LL << exp) - 1LL;
+      const long long delta_size = delta_size_ - bias;
+
+      frame_size += delta_size;
+
+      if (frame_size <= 0)
+        return E_FILE_FORMAT_INVALID;
+
+      if (frame_size > LONG_MAX)
+        return E_FILE_FORMAT_INVALID;
+
+      curr.len = static_cast<long>(frame_size);
+      size += curr.len;  // contribution of this frame
+
+      --frame_count;
+    }
+
+    // parse last frame
+    if (frame_count > 0) {
+      if (pos > stop || pf >= pf_end)
+        return E_FILE_FORMAT_INVALID;
+
+      const Frame& prev = *pf++;
+      assert(prev.len == frame_size);
+      if (prev.len != frame_size)
+        return E_FILE_FORMAT_INVALID;
+
+      if (pf >= pf_end)
+        return E_FILE_FORMAT_INVALID;
+
+      Frame& curr = *pf++;
+      if (pf != pf_end)
+        return E_FILE_FORMAT_INVALID;
+
+      curr.pos = 0;  // patch later
+
+      const long long total_size = stop - pos;
+
+      if (total_size < size)
+        return E_FILE_FORMAT_INVALID;
+
+      frame_size = total_size - size;
+
+      if (frame_size > LONG_MAX || frame_size <= 0)
+        return E_FILE_FORMAT_INVALID;
+
+      curr.len = static_cast<long>(frame_size);
+    }
+
+    pf = m_frames;
+    while (pf != pf_end) {
+      Frame& f = *pf++;
+      assert((pos + f.len) <= stop);
+      if ((pos + f.len) > stop)
+        return E_FILE_FORMAT_INVALID;
+
+      f.pos = pos;
+      pos += f.len;
+    }
+
+    if (pos != stop)
+      return E_FILE_FORMAT_INVALID;
+  }
+
+  return 0;  // success
+}
+
+long long Block::GetTimeCode(const Cluster* pCluster) const {
+  if (pCluster == 0)
+    return m_timecode;
+
+  const long long tc0 = pCluster->GetTimeCode();
+  assert(tc0 >= 0);
+
+  const long long tc = tc0 + m_timecode;
+
+  return tc;  // unscaled timecode units
+}
+
+long long Block::GetTime(const Cluster* pCluster) const {
+  assert(pCluster);
+
+  const long long tc = GetTimeCode(pCluster);
+
+  const Segment* const pSegment = pCluster->m_pSegment;
+  const SegmentInfo* const pInfo = pSegment->GetInfo();
+  assert(pInfo);
+
+  const long long scale = pInfo->GetTimeCodeScale();
+  assert(scale >= 1);
+
+  const long long ns = tc * scale;
+
+  return ns;
+}
+
+long long Block::GetTrackNumber() const { return m_track; }
+
+bool Block::IsKey() const {
+  return ((m_flags & static_cast<unsigned char>(1 << 7)) != 0);
+}
+
+void Block::SetKey(bool bKey) {
+  if (bKey)
+    m_flags |= static_cast<unsigned char>(1 << 7);
+  else
+    m_flags &= 0x7F;
+}
+
+bool Block::IsInvisible() const { return bool(int(m_flags & 0x08) != 0); }
+
+Block::Lacing Block::GetLacing() const {
+  const int value = int(m_flags & 0x06) >> 1;
+  return static_cast<Lacing>(value);
+}
+
+int Block::GetFrameCount() const { return m_frame_count; }
+
+const Block::Frame& Block::GetFrame(int idx) const {
+  assert(idx >= 0);
+  assert(idx < m_frame_count);
+
+  const Frame& f = m_frames[idx];
+  assert(f.pos > 0);
+  assert(f.len > 0);
+
+  return f;
+}
+
+long Block::Frame::Read(IMkvReader* pReader, unsigned char* buf) const {
+  assert(pReader);
+  assert(buf);
+
+  const long status = pReader->Read(pos, len, buf);
+  return status;
+}
+
+long long Block::GetDiscardPadding() const { return m_discard_padding; }
+
+}  // namespace mkvparser
diff --git a/thirdparty/libsimplewebm/libwebm/mkvparser/mkvparser.h b/thirdparty/libsimplewebm/libwebm/mkvparser/mkvparser.h
new file mode 100644
index 0000000000..1ef274b162
--- /dev/null
+++ b/thirdparty/libsimplewebm/libwebm/mkvparser/mkvparser.h
@@ -0,0 +1,1111 @@
+// Copyright (c) 2012 The WebM project authors. All Rights Reserved.
+//
+// Use of this source code is governed by a BSD-style license
+// that can be found in the LICENSE file in the root of the source
+// tree. An additional intellectual property rights grant can be found
+// in the file PATENTS.  All contributing project authors may
+// be found in the AUTHORS file in the root of the source tree.
+#ifndef MKVPARSER_MKVPARSER_H_
+#define MKVPARSER_MKVPARSER_H_
+
+#include <stddef.h>
+
+namespace mkvparser {
+
+const int E_PARSE_FAILED = -1;
+const int E_FILE_FORMAT_INVALID = -2;
+const int E_BUFFER_NOT_FULL = -3;
+
+class IMkvReader {
+ public:
+  virtual int Read(long long pos, long len, unsigned char* buf) = 0;
+  virtual int Length(long long* total, long long* available) = 0;
+
+  virtual ~IMkvReader();
+};
+
+template <typename Type>
+Type* SafeArrayAlloc(unsigned long long num_elements,
+                     unsigned long long element_size);
+long long GetUIntLength(IMkvReader*, long long, long&);
+long long ReadUInt(IMkvReader*, long long, long&);
+long long ReadID(IMkvReader* pReader, long long pos, long& len);
+long long UnserializeUInt(IMkvReader*, long long pos, long long size);
+
+long UnserializeFloat(IMkvReader*, long long pos, long long size, double&);
+long UnserializeInt(IMkvReader*, long long pos, long long size,
+                    long long& result);
+
+long UnserializeString(IMkvReader*, long long pos, long long size, char*& str);
+
+long ParseElementHeader(IMkvReader* pReader,
+                        long long& pos,  // consume id and size fields
+                        long long stop,  // if you know size of element's parent
+                        long long& id, long long& size);
+
+bool Match(IMkvReader*, long long&, unsigned long, long long&);
+bool Match(IMkvReader*, long long&, unsigned long, unsigned char*&, size_t&);
+
+void GetVersion(int& major, int& minor, int& build, int& revision);
+
+struct EBMLHeader {
+  EBMLHeader();
+  ~EBMLHeader();
+  long long m_version;
+  long long m_readVersion;
+  long long m_maxIdLength;
+  long long m_maxSizeLength;
+  char* m_docType;
+  long long m_docTypeVersion;
+  long long m_docTypeReadVersion;
+
+  long long Parse(IMkvReader*, long long&);
+  void Init();
+};
+
+class Segment;
+class Track;
+class Cluster;
+
+class Block {
+  Block(const Block&);
+  Block& operator=(const Block&);
+
+ public:
+  const long long m_start;
+  const long long m_size;
+
+  Block(long long start, long long size, long long discard_padding);
+  ~Block();
+
+  long Parse(const Cluster*);
+
+  long long GetTrackNumber() const;
+  long long GetTimeCode(const Cluster*) const;  // absolute, but not scaled
+  long long GetTime(const Cluster*) const;  // absolute, and scaled (ns)
+  bool IsKey() const;
+  void SetKey(bool);
+  bool IsInvisible() const;
+
+  enum Lacing { kLacingNone, kLacingXiph, kLacingFixed, kLacingEbml };
+  Lacing GetLacing() const;
+
+  int GetFrameCount() const;  // to index frames: [0, count)
+
+  struct Frame {
+    long long pos;  // absolute offset
+    long len;
+
+    long Read(IMkvReader*, unsigned char*) const;
+  };
+
+  const Frame& GetFrame(int frame_index) const;
+
+  long long GetDiscardPadding() const;
+
+ private:
+  long long m_track;  // Track::Number()
+  short m_timecode;  // relative to cluster
+  unsigned char m_flags;
+
+  Frame* m_frames;
+  int m_frame_count;
+
+ protected:
+  const long long m_discard_padding;
+};
+
+class BlockEntry {
+  BlockEntry(const BlockEntry&);
+  BlockEntry& operator=(const BlockEntry&);
+
+ protected:
+  BlockEntry(Cluster*, long index);
+
+ public:
+  virtual ~BlockEntry();
+
+  bool EOS() const { return (GetKind() == kBlockEOS); }
+  const Cluster* GetCluster() const;
+  long GetIndex() const;
+  virtual const Block* GetBlock() const = 0;
+
+  enum Kind { kBlockEOS, kBlockSimple, kBlockGroup };
+  virtual Kind GetKind() const = 0;
+
+ protected:
+  Cluster* const m_pCluster;
+  const long m_index;
+};
+
+class SimpleBlock : public BlockEntry {
+  SimpleBlock(const SimpleBlock&);
+  SimpleBlock& operator=(const SimpleBlock&);
+
+ public:
+  SimpleBlock(Cluster*, long index, long long start, long long size);
+  long Parse();
+
+  Kind GetKind() const;
+  const Block* GetBlock() const;
+
+ protected:
+  Block m_block;
+};
+
+class BlockGroup : public BlockEntry {
+  BlockGroup(const BlockGroup&);
+  BlockGroup& operator=(const BlockGroup&);
+
+ public:
+  BlockGroup(Cluster*, long index,
+             long long block_start,  // absolute pos of block's payload
+             long long block_size,  // size of block's payload
+             long long prev, long long next, long long duration,
+             long long discard_padding);
+
+  long Parse();
+
+  Kind GetKind() const;
+  const Block* GetBlock() const;
+
+  long long GetPrevTimeCode() const;  // relative to block's time
+  long long GetNextTimeCode() const;  // as above
+  long long GetDurationTimeCode() const;
+
+ private:
+  Block m_block;
+  const long long m_prev;
+  const long long m_next;
+  const long long m_duration;
+};
+
+///////////////////////////////////////////////////////////////
+// ContentEncoding element
+// Elements used to describe if the track data has been encrypted or
+// compressed with zlib or header stripping.
+class ContentEncoding {
+ public:
+  enum { kCTR = 1 };
+
+  ContentEncoding();
+  ~ContentEncoding();
+
+  // ContentCompression element names
+  struct ContentCompression {
+    ContentCompression();
+    ~ContentCompression();
+
+    unsigned long long algo;
+    unsigned char* settings;
+    long long settings_len;
+  };
+
+  // ContentEncAESSettings element names
+  struct ContentEncAESSettings {
+    ContentEncAESSettings() : cipher_mode(kCTR) {}
+    ~ContentEncAESSettings() {}
+
+    unsigned long long cipher_mode;
+  };
+
+  // ContentEncryption element names
+  struct ContentEncryption {
+    ContentEncryption();
+    ~ContentEncryption();
+
+    unsigned long long algo;
+    unsigned char* key_id;
+    long long key_id_len;
+    unsigned char* signature;
+    long long signature_len;
+    unsigned char* sig_key_id;
+    long long sig_key_id_len;
+    unsigned long long sig_algo;
+    unsigned long long sig_hash_algo;
+
+    ContentEncAESSettings aes_settings;
+  };
+
+  // Returns ContentCompression represented by |idx|. Returns NULL if |idx|
+  // is out of bounds.
+  const ContentCompression* GetCompressionByIndex(unsigned long idx) const;
+
+  // Returns number of ContentCompression elements in this ContentEncoding
+  // element.
+  unsigned long GetCompressionCount() const;
+
+  // Parses the ContentCompression element from |pReader|. |start| is the
+  // starting offset of the ContentCompression payload. |size| is the size in
+  // bytes of the ContentCompression payload. |compression| is where the parsed
+  // values will be stored.
+  long ParseCompressionEntry(long long start, long long size,
+                             IMkvReader* pReader,
+                             ContentCompression* compression);
+
+  // Returns ContentEncryption represented by |idx|. Returns NULL if |idx|
+  // is out of bounds.
+  const ContentEncryption* GetEncryptionByIndex(unsigned long idx) const;
+
+  // Returns number of ContentEncryption elements in this ContentEncoding
+  // element.
+  unsigned long GetEncryptionCount() const;
+
+  // Parses the ContentEncAESSettings element from |pReader|. |start| is the
+  // starting offset of the ContentEncAESSettings payload. |size| is the
+  // size in bytes of the ContentEncAESSettings payload. |encryption| is
+  // where the parsed values will be stored.
+  long ParseContentEncAESSettingsEntry(long long start, long long size,
+                                       IMkvReader* pReader,
+                                       ContentEncAESSettings* aes);
+
+  // Parses the ContentEncoding element from |pReader|. |start| is the
+  // starting offset of the ContentEncoding payload. |size| is the size in
+  // bytes of the ContentEncoding payload. Returns true on success.
+  long ParseContentEncodingEntry(long long start, long long size,
+                                 IMkvReader* pReader);
+
+  // Parses the ContentEncryption element from |pReader|. |start| is the
+  // starting offset of the ContentEncryption payload. |size| is the size in
+  // bytes of the ContentEncryption payload. |encryption| is where the parsed
+  // values will be stored.
+  long ParseEncryptionEntry(long long start, long long size,
+                            IMkvReader* pReader, ContentEncryption* encryption);
+
+  unsigned long long encoding_order() const { return encoding_order_; }
+  unsigned long long encoding_scope() const { return encoding_scope_; }
+  unsigned long long encoding_type() const { return encoding_type_; }
+
+ private:
+  // Member variables for list of ContentCompression elements.
+  ContentCompression** compression_entries_;
+  ContentCompression** compression_entries_end_;
+
+  // Member variables for list of ContentEncryption elements.
+  ContentEncryption** encryption_entries_;
+  ContentEncryption** encryption_entries_end_;
+
+  // ContentEncoding element names
+  unsigned long long encoding_order_;
+  unsigned long long encoding_scope_;
+  unsigned long long encoding_type_;
+
+  // LIBWEBM_DISALLOW_COPY_AND_ASSIGN(ContentEncoding);
+  ContentEncoding(const ContentEncoding&);
+  ContentEncoding& operator=(const ContentEncoding&);
+};
+
+class Track {
+  Track(const Track&);
+  Track& operator=(const Track&);
+
+ public:
+  class Info;
+  static long Create(Segment*, const Info&, long long element_start,
+                     long long element_size, Track*&);
+
+  enum Type { kVideo = 1, kAudio = 2, kSubtitle = 0x11, kMetadata = 0x21 };
+
+  Segment* const m_pSegment;
+  const long long m_element_start;
+  const long long m_element_size;
+  virtual ~Track();
+
+  long GetType() const;
+  long GetNumber() const;
+  unsigned long long GetUid() const;
+  const char* GetNameAsUTF8() const;
+  const char* GetLanguage() const;
+  const char* GetCodecNameAsUTF8() const;
+  const char* GetCodecId() const;
+  const unsigned char* GetCodecPrivate(size_t&) const;
+  bool GetLacing() const;
+  unsigned long long GetDefaultDuration() const;
+  unsigned long long GetCodecDelay() const;
+  unsigned long long GetSeekPreRoll() const;
+
+  const BlockEntry* GetEOS() const;
+
+  struct Settings {
+    long long start;
+    long long size;
+  };
+
+  class Info {
+   public:
+    Info();
+    ~Info();
+    int Copy(Info&) const;
+    void Clear();
+    long type;
+    long number;
+    unsigned long long uid;
+    unsigned long long defaultDuration;
+    unsigned long long codecDelay;
+    unsigned long long seekPreRoll;
+    char* nameAsUTF8;
+    char* language;
+    char* codecId;
+    char* codecNameAsUTF8;
+    unsigned char* codecPrivate;
+    size_t codecPrivateSize;
+    bool lacing;
+    Settings settings;
+
+   private:
+    Info(const Info&);
+    Info& operator=(const Info&);
+    int CopyStr(char* Info::*str, Info&) const;
+  };
+
+  long GetFirst(const BlockEntry*&) const;
+  long GetNext(const BlockEntry* pCurr, const BlockEntry*& pNext) const;
+  virtual bool VetEntry(const BlockEntry*) const;
+  virtual long Seek(long long time_ns, const BlockEntry*&) const;
+
+  const ContentEncoding* GetContentEncodingByIndex(unsigned long idx) const;
+  unsigned long GetContentEncodingCount() const;
+
+  long ParseContentEncodingsEntry(long long start, long long size);
+
+ protected:
+  Track(Segment*, long long element_start, long long element_size);
+
+  Info m_info;
+
+  class EOSBlock : public BlockEntry {
+   public:
+    EOSBlock();
+
+    Kind GetKind() const;
+    const Block* GetBlock() const;
+  };
+
+  EOSBlock m_eos;
+
+ private:
+  ContentEncoding** content_encoding_entries_;
+  ContentEncoding** content_encoding_entries_end_;
+};
+
+struct PrimaryChromaticity {
+  PrimaryChromaticity() : x(0), y(0) {}
+  ~PrimaryChromaticity() {}
+  static bool Parse(IMkvReader* reader, long long read_pos,
+                    long long value_size, bool is_x,
+                    PrimaryChromaticity** chromaticity);
+  float x;
+  float y;
+};
+
+struct MasteringMetadata {
+  static const float kValueNotPresent;
+
+  MasteringMetadata()
+      : r(NULL),
+        g(NULL),
+        b(NULL),
+        white_point(NULL),
+        luminance_max(kValueNotPresent),
+        luminance_min(kValueNotPresent) {}
+  ~MasteringMetadata() {
+    delete r;
+    delete g;
+    delete b;
+    delete white_point;
+  }
+
+  static bool Parse(IMkvReader* reader, long long element_start,
+                    long long element_size,
+                    MasteringMetadata** mastering_metadata);
+
+  PrimaryChromaticity* r;
+  PrimaryChromaticity* g;
+  PrimaryChromaticity* b;
+  PrimaryChromaticity* white_point;
+  float luminance_max;
+  float luminance_min;
+};
+
+struct Colour {
+  static const long long kValueNotPresent;
+
+  // Unless otherwise noted all values assigned upon construction are the
+  // equivalent of unspecified/default.
+  Colour()
+      : matrix_coefficients(kValueNotPresent),
+        bits_per_channel(kValueNotPresent),
+        chroma_subsampling_horz(kValueNotPresent),
+        chroma_subsampling_vert(kValueNotPresent),
+        cb_subsampling_horz(kValueNotPresent),
+        cb_subsampling_vert(kValueNotPresent),
+        chroma_siting_horz(kValueNotPresent),
+        chroma_siting_vert(kValueNotPresent),
+        range(kValueNotPresent),
+        transfer_characteristics(kValueNotPresent),
+        primaries(kValueNotPresent),
+        max_cll(kValueNotPresent),
+        max_fall(kValueNotPresent),
+        mastering_metadata(NULL) {}
+  ~Colour() {
+    delete mastering_metadata;
+    mastering_metadata = NULL;
+  }
+
+  static bool Parse(IMkvReader* reader, long long element_start,
+                    long long element_size, Colour** colour);
+
+  long long matrix_coefficients;
+  long long bits_per_channel;
+  long long chroma_subsampling_horz;
+  long long chroma_subsampling_vert;
+  long long cb_subsampling_horz;
+  long long cb_subsampling_vert;
+  long long chroma_siting_horz;
+  long long chroma_siting_vert;
+  long long range;
+  long long transfer_characteristics;
+  long long primaries;
+  long long max_cll;
+  long long max_fall;
+
+  MasteringMetadata* mastering_metadata;
+};
+
+class VideoTrack : public Track {
+  VideoTrack(const VideoTrack&);
+  VideoTrack& operator=(const VideoTrack&);
+
+  VideoTrack(Segment*, long long element_start, long long element_size);
+
+ public:
+  virtual ~VideoTrack();
+  static long Parse(Segment*, const Info&, long long element_start,
+                    long long element_size, VideoTrack*&);
+
+  long long GetWidth() const;
+  long long GetHeight() const;
+  long long GetDisplayWidth() const;
+  long long GetDisplayHeight() const;
+  long long GetDisplayUnit() const;
+  long long GetStereoMode() const;
+  double GetFrameRate() const;
+
+  bool VetEntry(const BlockEntry*) const;
+  long Seek(long long time_ns, const BlockEntry*&) const;
+
+  Colour* GetColour() const;
+
+ private:
+  long long m_width;
+  long long m_height;
+  long long m_display_width;
+  long long m_display_height;
+  long long m_display_unit;
+  long long m_stereo_mode;
+
+  double m_rate;
+
+  Colour* m_colour;
+};
+
+class AudioTrack : public Track {
+  AudioTrack(const AudioTrack&);
+  AudioTrack& operator=(const AudioTrack&);
+
+  AudioTrack(Segment*, long long element_start, long long element_size);
+
+ public:
+  static long Parse(Segment*, const Info&, long long element_start,
+                    long long element_size, AudioTrack*&);
+
+  double GetSamplingRate() const;
+  long long GetChannels() const;
+  long long GetBitDepth() const;
+
+ private:
+  double m_rate;
+  long long m_channels;
+  long long m_bitDepth;
+};
+
+class Tracks {
+  Tracks(const Tracks&);
+  Tracks& operator=(const Tracks&);
+
+ public:
+  Segment* const m_pSegment;
+  const long long m_start;
+  const long long m_size;
+  const long long m_element_start;
+  const long long m_element_size;
+
+  Tracks(Segment*, long long start, long long size, long long element_start,
+         long long element_size);
+
+  ~Tracks();
+
+  long Parse();
+
+  unsigned long GetTracksCount() const;
+
+  const Track* GetTrackByNumber(long tn) const;
+  const Track* GetTrackByIndex(unsigned long idx) const;
+
+ private:
+  Track** m_trackEntries;
+  Track** m_trackEntriesEnd;
+
+  long ParseTrackEntry(long long payload_start, long long payload_size,
+                       long long element_start, long long element_size,
+                       Track*&) const;
+};
+
+class Chapters {
+  Chapters(const Chapters&);
+  Chapters& operator=(const Chapters&);
+
+ public:
+  Segment* const m_pSegment;
+  const long long m_start;
+  const long long m_size;
+  const long long m_element_start;
+  const long long m_element_size;
+
+  Chapters(Segment*, long long payload_start, long long payload_size,
+           long long element_start, long long element_size);
+
+  ~Chapters();
+
+  long Parse();
+
+  class Atom;
+  class Edition;
+
+  class Display {
+    friend class Atom;
+    Display();
+    Display(const Display&);
+    ~Display();
+    Display& operator=(const Display&);
+
+   public:
+    const char* GetString() const;
+    const char* GetLanguage() const;
+    const char* GetCountry() const;
+
+   private:
+    void Init();
+    void ShallowCopy(Display&) const;
+    void Clear();
+    long Parse(IMkvReader*, long long pos, long long size);
+
+    char* m_string;
+    char* m_language;
+    char* m_country;
+  };
+
+  class Atom {
+    friend class Edition;
+    Atom();
+    Atom(const Atom&);
+    ~Atom();
+    Atom& operator=(const Atom&);
+
+   public:
+    unsigned long long GetUID() const;
+    const char* GetStringUID() const;
+
+    long long GetStartTimecode() const;
+    long long GetStopTimecode() const;
+
+    long long GetStartTime(const Chapters*) const;
+    long long GetStopTime(const Chapters*) const;
+
+    int GetDisplayCount() const;
+    const Display* GetDisplay(int index) const;
+
+   private:
+    void Init();
+    void ShallowCopy(Atom&) const;
+    void Clear();
+    long Parse(IMkvReader*, long long pos, long long size);
+    static long long GetTime(const Chapters*, long long timecode);
+
+    long ParseDisplay(IMkvReader*, long long pos, long long size);
+    bool ExpandDisplaysArray();
+
+    char* m_string_uid;
+    unsigned long long m_uid;
+    long long m_start_timecode;
+    long long m_stop_timecode;
+
+    Display* m_displays;
+    int m_displays_size;
+    int m_displays_count;
+  };
+
+  class Edition {
+    friend class Chapters;
+    Edition();
+    Edition(const Edition&);
+    ~Edition();
+    Edition& operator=(const Edition&);
+
+   public:
+    int GetAtomCount() const;
+    const Atom* GetAtom(int index) const;
+
+   private:
+    void Init();
+    void ShallowCopy(Edition&) const;
+    void Clear();
+    long Parse(IMkvReader*, long long pos, long long size);
+
+    long ParseAtom(IMkvReader*, long long pos, long long size);
+    bool ExpandAtomsArray();
+
+    Atom* m_atoms;
+    int m_atoms_size;
+    int m_atoms_count;
+  };
+
+  int GetEditionCount() const;
+  const Edition* GetEdition(int index) const;
+
+ private:
+  long ParseEdition(long long pos, long long size);
+  bool ExpandEditionsArray();
+
+  Edition* m_editions;
+  int m_editions_size;
+  int m_editions_count;
+};
+
+class Tags {
+  Tags(const Tags&);
+  Tags& operator=(const Tags&);
+
+ public:
+  Segment* const m_pSegment;
+  const long long m_start;
+  const long long m_size;
+  const long long m_element_start;
+  const long long m_element_size;
+
+  Tags(Segment*, long long payload_start, long long payload_size,
+       long long element_start, long long element_size);
+
+  ~Tags();
+
+  long Parse();
+
+  class Tag;
+  class SimpleTag;
+
+  class SimpleTag {
+    friend class Tag;
+    SimpleTag();
+    SimpleTag(const SimpleTag&);
+    ~SimpleTag();
+    SimpleTag& operator=(const SimpleTag&);
+
+   public:
+    const char* GetTagName() const;
+    const char* GetTagString() const;
+
+   private:
+    void Init();
+    void ShallowCopy(SimpleTag&) const;
+    void Clear();
+    long Parse(IMkvReader*, long long pos, long long size);
+
+    char* m_tag_name;
+    char* m_tag_string;
+  };
+
+  class Tag {
+    friend class Tags;
+    Tag();
+    Tag(const Tag&);
+    ~Tag();
+    Tag& operator=(const Tag&);
+
+   public:
+    int GetSimpleTagCount() const;
+    const SimpleTag* GetSimpleTag(int index) const;
+
+   private:
+    void Init();
+    void ShallowCopy(Tag&) const;
+    void Clear();
+    long Parse(IMkvReader*, long long pos, long long size);
+
+    long ParseSimpleTag(IMkvReader*, long long pos, long long size);
+    bool ExpandSimpleTagsArray();
+
+    SimpleTag* m_simple_tags;
+    int m_simple_tags_size;
+    int m_simple_tags_count;
+  };
+
+  int GetTagCount() const;
+  const Tag* GetTag(int index) const;
+
+ private:
+  long ParseTag(long long pos, long long size);
+  bool ExpandTagsArray();
+
+  Tag* m_tags;
+  int m_tags_size;
+  int m_tags_count;
+};
+
+class SegmentInfo {
+  SegmentInfo(const SegmentInfo&);
+  SegmentInfo& operator=(const SegmentInfo&);
+
+ public:
+  Segment* const m_pSegment;
+  const long long m_start;
+  const long long m_size;
+  const long long m_element_start;
+  const long long m_element_size;
+
+  SegmentInfo(Segment*, long long start, long long size,
+              long long element_start, long long element_size);
+
+  ~SegmentInfo();
+
+  long Parse();
+
+  long long GetTimeCodeScale() const;
+  long long GetDuration() const;  // scaled
+  const char* GetMuxingAppAsUTF8() const;
+  const char* GetWritingAppAsUTF8() const;
+  const char* GetTitleAsUTF8() const;
+
+ private:
+  long long m_timecodeScale;
+  double m_duration;
+  char* m_pMuxingAppAsUTF8;
+  char* m_pWritingAppAsUTF8;
+  char* m_pTitleAsUTF8;
+};
+
+class SeekHead {
+  SeekHead(const SeekHead&);
+  SeekHead& operator=(const SeekHead&);
+
+ public:
+  Segment* const m_pSegment;
+  const long long m_start;
+  const long long m_size;
+  const long long m_element_start;
+  const long long m_element_size;
+
+  SeekHead(Segment*, long long start, long long size, long long element_start,
+           long long element_size);
+
+  ~SeekHead();
+
+  long Parse();
+
+  struct Entry {
+    // the SeekHead entry payload
+    long long id;
+    long long pos;
+
+    // absolute pos of SeekEntry ID
+    long long element_start;
+
+    // SeekEntry ID size + size size + payload
+    long long element_size;
+  };
+
+  int GetCount() const;
+  const Entry* GetEntry(int idx) const;
+
+  struct VoidElement {
+    // absolute pos of Void ID
+    long long element_start;
+
+    // ID size + size size + payload size
+    long long element_size;
+  };
+
+  int GetVoidElementCount() const;
+  const VoidElement* GetVoidElement(int idx) const;
+
+ private:
+  Entry* m_entries;
+  int m_entry_count;
+
+  VoidElement* m_void_elements;
+  int m_void_element_count;
+
+  static bool ParseEntry(IMkvReader*,
+                         long long pos,  // payload
+                         long long size, Entry*);
+};
+
+class Cues;
+class CuePoint {
+  friend class Cues;
+
+  CuePoint(long, long long);
+  ~CuePoint();
+
+  CuePoint(const CuePoint&);
+  CuePoint& operator=(const CuePoint&);
+
+ public:
+  long long m_element_start;
+  long long m_element_size;
+
+  bool Load(IMkvReader*);
+
+  long long GetTimeCode() const;  // absolute but unscaled
+  long long GetTime(const Segment*) const;  // absolute and scaled (ns units)
+
+  struct TrackPosition {
+    long long m_track;
+    long long m_pos;  // of cluster
+    long long m_block;
+    // codec_state  //defaults to 0
+    // reference = clusters containing req'd referenced blocks
+    //  reftime = timecode of the referenced block
+
+    bool Parse(IMkvReader*, long long, long long);
+  };
+
+  const TrackPosition* Find(const Track*) const;
+
+ private:
+  const long m_index;
+  long long m_timecode;
+  TrackPosition* m_track_positions;
+  size_t m_track_positions_count;
+};
+
+class Cues {
+  friend class Segment;
+
+  Cues(Segment*, long long start, long long size, long long element_start,
+       long long element_size);
+  ~Cues();
+
+  Cues(const Cues&);
+  Cues& operator=(const Cues&);
+
+ public:
+  Segment* const m_pSegment;
+  const long long m_start;
+  const long long m_size;
+  const long long m_element_start;
+  const long long m_element_size;
+
+  bool Find(  // lower bound of time_ns
+      long long time_ns, const Track*, const CuePoint*&,
+      const CuePoint::TrackPosition*&) const;
+
+  const CuePoint* GetFirst() const;
+  const CuePoint* GetLast() const;
+  const CuePoint* GetNext(const CuePoint*) const;
+
+  const BlockEntry* GetBlock(const CuePoint*,
+                             const CuePoint::TrackPosition*) const;
+
+  bool LoadCuePoint() const;
+  long GetCount() const;  // loaded only
+  // long GetTotal() const;  //loaded + preloaded
+  bool DoneParsing() const;
+
+ private:
+  bool Init() const;
+  bool PreloadCuePoint(long&, long long) const;
+
+  mutable CuePoint** m_cue_points;
+  mutable long m_count;
+  mutable long m_preload_count;
+  mutable long long m_pos;
+};
+
+class Cluster {
+  friend class Segment;
+
+  Cluster(const Cluster&);
+  Cluster& operator=(const Cluster&);
+
+ public:
+  Segment* const m_pSegment;
+
+ public:
+  static Cluster* Create(Segment*,
+                         long index,  // index in segment
+                         long long off);  // offset relative to segment
+  // long long element_size);
+
+  Cluster();  // EndOfStream
+  ~Cluster();
+
+  bool EOS() const;
+
+  long long GetTimeCode() const;  // absolute, but not scaled
+  long long GetTime() const;  // absolute, and scaled (nanosecond units)
+  long long GetFirstTime() const;  // time (ns) of first (earliest) block
+  long long GetLastTime() const;  // time (ns) of last (latest) block
+
+  long GetFirst(const BlockEntry*&) const;
+  long GetLast(const BlockEntry*&) const;
+  long GetNext(const BlockEntry* curr, const BlockEntry*& next) const;
+
+  const BlockEntry* GetEntry(const Track*, long long ns = -1) const;
+  const BlockEntry* GetEntry(const CuePoint&,
+                             const CuePoint::TrackPosition&) const;
+  // const BlockEntry* GetMaxKey(const VideoTrack*) const;
+
+  //    static bool HasBlockEntries(const Segment*, long long);
+
+  static long HasBlockEntries(const Segment*, long long idoff, long long& pos,
+                              long& size);
+
+  long GetEntryCount() const;
+
+  long Load(long long& pos, long& size) const;
+
+  long Parse(long long& pos, long& size) const;
+  long GetEntry(long index, const mkvparser::BlockEntry*&) const;
+
+ protected:
+  Cluster(Segment*, long index, long long element_start);
+  // long long element_size);
+
+ public:
+  const long long m_element_start;
+  long long GetPosition() const;  // offset relative to segment
+
+  long GetIndex() const;
+  long long GetElementSize() const;
+  // long long GetPayloadSize() const;
+
+  // long long Unparsed() const;
+
+ private:
+  long m_index;
+  mutable long long m_pos;
+  // mutable long long m_size;
+  mutable long long m_element_size;
+  mutable long long m_timecode;
+  mutable BlockEntry** m_entries;
+  mutable long m_entries_size;
+  mutable long m_entries_count;
+
+  long ParseSimpleBlock(long long, long long&, long&);
+  long ParseBlockGroup(long long, long long&, long&);
+
+  long CreateBlock(long long id, long long pos, long long size,
+                   long long discard_padding);
+  long CreateBlockGroup(long long start_offset, long long size,
+                        long long discard_padding);
+  long CreateSimpleBlock(long long, long long);
+};
+
+class Segment {
+  friend class Cues;
+  friend class Track;
+  friend class VideoTrack;
+
+  Segment(const Segment&);
+  Segment& operator=(const Segment&);
+
+ private:
+  Segment(IMkvReader*, long long elem_start,
+          // long long elem_size,
+          long long pos, long long size);
+
+ public:
+  IMkvReader* const m_pReader;
+  const long long m_element_start;
+  // const long long m_element_size;
+  const long long m_start;  // posn of segment payload
+  const long long m_size;  // size of segment payload
+  Cluster m_eos;  // TODO: make private?
+
+  static long long CreateInstance(IMkvReader*, long long, Segment*&);
+  ~Segment();
+
+  long Load();  // loads headers and all clusters
+
+  // for incremental loading
+  // long long Unparsed() const;
+  bool DoneParsing() const;
+  long long ParseHeaders();  // stops when first cluster is found
+  // long FindNextCluster(long long& pos, long& size) const;
+  long LoadCluster(long long& pos, long& size);  // load one cluster
+  long LoadCluster();
+
+  long ParseNext(const Cluster* pCurr, const Cluster*& pNext, long long& pos,
+                 long& size);
+
+  const SeekHead* GetSeekHead() const;
+  const Tracks* GetTracks() const;
+  const SegmentInfo* GetInfo() const;
+  const Cues* GetCues() const;
+  const Chapters* GetChapters() const;
+  const Tags* GetTags() const;
+
+  long long GetDuration() const;
+
+  unsigned long GetCount() const;
+  const Cluster* GetFirst() const;
+  const Cluster* GetLast() const;
+  const Cluster* GetNext(const Cluster*);
+
+  const Cluster* FindCluster(long long time_nanoseconds) const;
+  // const BlockEntry* Seek(long long time_nanoseconds, const Track*) const;
+
+  const Cluster* FindOrPreloadCluster(long long pos);
+
+  long ParseCues(long long cues_off,  // offset relative to start of segment
+                 long long& parse_pos, long& parse_len);
+
+ private:
+  long long m_pos;  // absolute file posn; what has been consumed so far
+  Cluster* m_pUnknownSize;
+
+  SeekHead* m_pSeekHead;
+  SegmentInfo* m_pInfo;
+  Tracks* m_pTracks;
+  Cues* m_pCues;
+  Chapters* m_pChapters;
+  Tags* m_pTags;
+  Cluster** m_clusters;
+  long m_clusterCount;  // number of entries for which m_index >= 0
+  long m_clusterPreloadCount;  // number of entries for which m_index < 0
+  long m_clusterSize;  // array size
+
+  long DoLoadCluster(long long&, long&);
+  long DoLoadClusterUnknownSize(long long&, long&);
+  long DoParseNext(const Cluster*&, long long&, long&);
+
+  bool AppendCluster(Cluster*);
+  bool PreloadCluster(Cluster*, ptrdiff_t);
+
+  // void ParseSeekHead(long long pos, long long size);
+  // void ParseSeekEntry(long long pos, long long size);
+  // void ParseCues(long long);
+
+  const BlockEntry* GetBlock(const CuePoint&, const CuePoint::TrackPosition&);
+};
+
+}  // namespace mkvparser
+
+inline long mkvparser::Segment::LoadCluster() {
+  long long pos;
+  long size;
+
+  return LoadCluster(pos, size);
+}
+
+#endif  // MKVPARSER_MKVPARSER_H_