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Diffstat (limited to 'thirdparty/libwebp/dec/quant.c')
| -rw-r--r-- | thirdparty/libwebp/dec/quant.c | 110 |
1 files changed, 110 insertions, 0 deletions
diff --git a/thirdparty/libwebp/dec/quant.c b/thirdparty/libwebp/dec/quant.c new file mode 100644 index 0000000000..5b648f942c --- /dev/null +++ b/thirdparty/libwebp/dec/quant.c @@ -0,0 +1,110 @@ +// Copyright 2010 Google Inc. All Rights Reserved. +// +// Use of this source code is governed by a BSD-style license +// that can be found in the COPYING 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. +// ----------------------------------------------------------------------------- +// +// Quantizer initialization +// +// Author: Skal (pascal.massimino@gmail.com) + +#include "./vp8i.h" + +static WEBP_INLINE int clip(int v, int M) { + return v < 0 ? 0 : v > M ? M : v; +} + +// Paragraph 14.1 +static const uint8_t kDcTable[128] = { + 4, 5, 6, 7, 8, 9, 10, 10, + 11, 12, 13, 14, 15, 16, 17, 17, + 18, 19, 20, 20, 21, 21, 22, 22, + 23, 23, 24, 25, 25, 26, 27, 28, + 29, 30, 31, 32, 33, 34, 35, 36, + 37, 37, 38, 39, 40, 41, 42, 43, + 44, 45, 46, 46, 47, 48, 49, 50, + 51, 52, 53, 54, 55, 56, 57, 58, + 59, 60, 61, 62, 63, 64, 65, 66, + 67, 68, 69, 70, 71, 72, 73, 74, + 75, 76, 76, 77, 78, 79, 80, 81, + 82, 83, 84, 85, 86, 87, 88, 89, + 91, 93, 95, 96, 98, 100, 101, 102, + 104, 106, 108, 110, 112, 114, 116, 118, + 122, 124, 126, 128, 130, 132, 134, 136, + 138, 140, 143, 145, 148, 151, 154, 157 +}; + +static const uint16_t kAcTable[128] = { + 4, 5, 6, 7, 8, 9, 10, 11, + 12, 13, 14, 15, 16, 17, 18, 19, + 20, 21, 22, 23, 24, 25, 26, 27, + 28, 29, 30, 31, 32, 33, 34, 35, + 36, 37, 38, 39, 40, 41, 42, 43, + 44, 45, 46, 47, 48, 49, 50, 51, + 52, 53, 54, 55, 56, 57, 58, 60, + 62, 64, 66, 68, 70, 72, 74, 76, + 78, 80, 82, 84, 86, 88, 90, 92, + 94, 96, 98, 100, 102, 104, 106, 108, + 110, 112, 114, 116, 119, 122, 125, 128, + 131, 134, 137, 140, 143, 146, 149, 152, + 155, 158, 161, 164, 167, 170, 173, 177, + 181, 185, 189, 193, 197, 201, 205, 209, + 213, 217, 221, 225, 229, 234, 239, 245, + 249, 254, 259, 264, 269, 274, 279, 284 +}; + +//------------------------------------------------------------------------------ +// Paragraph 9.6 + +void VP8ParseQuant(VP8Decoder* const dec) { + VP8BitReader* const br = &dec->br_; + const int base_q0 = VP8GetValue(br, 7); + const int dqy1_dc = VP8Get(br) ? VP8GetSignedValue(br, 4) : 0; + const int dqy2_dc = VP8Get(br) ? VP8GetSignedValue(br, 4) : 0; + const int dqy2_ac = VP8Get(br) ? VP8GetSignedValue(br, 4) : 0; + const int dquv_dc = VP8Get(br) ? VP8GetSignedValue(br, 4) : 0; + const int dquv_ac = VP8Get(br) ? VP8GetSignedValue(br, 4) : 0; + + const VP8SegmentHeader* const hdr = &dec->segment_hdr_; + int i; + + for (i = 0; i < NUM_MB_SEGMENTS; ++i) { + int q; + if (hdr->use_segment_) { + q = hdr->quantizer_[i]; + if (!hdr->absolute_delta_) { + q += base_q0; + } + } else { + if (i > 0) { + dec->dqm_[i] = dec->dqm_[0]; + continue; + } else { + q = base_q0; + } + } + { + VP8QuantMatrix* const m = &dec->dqm_[i]; + m->y1_mat_[0] = kDcTable[clip(q + dqy1_dc, 127)]; + m->y1_mat_[1] = kAcTable[clip(q + 0, 127)]; + + m->y2_mat_[0] = kDcTable[clip(q + dqy2_dc, 127)] * 2; + // For all x in [0..284], x*155/100 is bitwise equal to (x*101581) >> 16. + // The smallest precision for that is '(x*6349) >> 12' but 16 is a good + // word size. + m->y2_mat_[1] = (kAcTable[clip(q + dqy2_ac, 127)] * 101581) >> 16; + if (m->y2_mat_[1] < 8) m->y2_mat_[1] = 8; + + m->uv_mat_[0] = kDcTable[clip(q + dquv_dc, 117)]; + m->uv_mat_[1] = kAcTable[clip(q + dquv_ac, 127)]; + + m->uv_quant_ = q + dquv_ac; // for dithering strength evaluation + } + } +} + +//------------------------------------------------------------------------------ + |