2 files changed, 92 insertions, 3 deletions

diff --git a/platform/javascript/audio_driver_javascript.cpp b/platform/javascript/audio_driver_javascript.cpp
index 4c0e5fd966..cd3974669f 100644
--- a/platform/javascript/audio_driver_javascript.cpp
+++ b/platform/javascript/audio_driver_javascript.cpp
@@ -29,6 +29,7 @@
 /*************************************************************************/
 #include "audio_driver_javascript.h"
 
+#include <emscripten.h>
 #include <string.h>
 
 #define MAX_NUMBER_INTERFACES 3
@@ -38,22 +39,91 @@
 
 //AudioDriverJavaScript* AudioDriverJavaScript::s_ad=NULL;
 
+AudioDriverJavaScript *AudioDriverJavaScript::singleton_js = NULL;
 const char *AudioDriverJavaScript::get_name() const {
 
 	return "JavaScript";
 }
 
+extern "C" {
+
+void js_audio_driver_mix_function(int p_frames) {
+
+	//print_line("MIXI! "+itos(p_frames));
+	AudioDriverJavaScript::singleton_js->mix_to_js(p_frames);
+}
+}
+
+void AudioDriverJavaScript::mix_to_js(int p_frames) {
+
+	int todo = p_frames;
+	int offset = 0;
+
+	while (todo) {
+
+		int tomix = MIN(todo, INTERNAL_BUFFER_SIZE);
+
+		audio_server_process(p_frames, stream_buffer);
+		for (int i = 0; i < tomix * internal_buffer_channels; i++) {
+			internal_buffer[i] = float(stream_buffer[i] >> 16) * 32768.0;
+		}
+
+		/* clang-format off */
+		EM_ASM_({
+			var data = HEAPF32.subarray($0 / 4, $0 / 4 + $2 * 2);
+
+			for (var channel = 0; channel < _as_output_buffer.numberOfChannels; channel++) {
+				var outputData = _as_output_buffer.getChannelData(channel);
+				// Loop through samples
+				for (var sample = 0; sample < $2; sample++) {
+					// make output equal to the same as the input
+					outputData[sample + $1] = data[sample * 2 + channel];
+				}
+			}
+		}, internal_buffer, offset, tomix);
+		/* clang-format on */
+
+		todo -= tomix;
+		offset += tomix;
+	}
+}
+
 Error AudioDriverJavaScript::init() {
 
 	return OK;
 }
 
 void AudioDriverJavaScript::start() {
+
+	internal_buffer_channels = 2;
+	internal_buffer = memnew_arr(float, INTERNAL_BUFFER_SIZE *internal_buffer_channels);
+	stream_buffer = memnew_arr(int32_t, INTERNAL_BUFFER_SIZE * 4); //max 4 channels
+
+	/* clang-format off */
+	EM_ASM(
+			_as_audioctx = new (window.AudioContext || window.webkitAudioContext)();
+
+			audio_server_mix_function = Module.cwrap('js_audio_driver_mix_function', 'void', ['number']);
+		);
+
+	int buffer_latency = 16384;
+	EM_ASM_( {
+		_as_script_node = _as_audioctx.createScriptProcessor($0, 0, 2);
+		_as_script_node.connect(_as_audioctx.destination);
+		console.log(_as_script_node.bufferSize);
+
+		_as_script_node.onaudioprocess = function(audioProcessingEvent) {
+		// The output buffer contains the samples that will be modified and played
+			_as_output_buffer = audioProcessingEvent.outputBuffer;
+			audio_server_mix_function(_as_output_buffer.getChannelData(0).length);
+		}
+	}, buffer_latency);
+	/* clang-format on */
 }
 
 int AudioDriverJavaScript::get_mix_rate() const {
 
-	return 44100;
+	return mix_rate;
 }
 
 AudioDriver::SpeakerMode AudioDriverJavaScript::get_speaker_mode() const {
@@ -63,7 +133,7 @@ AudioDriver::SpeakerMode AudioDriverJavaScript::get_speaker_mode() const {
 
 void AudioDriverJavaScript::lock() {
 
-	/*
+	/*no locking, as threads are not supported
 	if (active && mutex)
 		mutex->lock();
 	*/
@@ -71,7 +141,7 @@ void AudioDriverJavaScript::lock() {
 
 void AudioDriverJavaScript::unlock() {
 
-	/*
+	/*no locking, as threads are not supported
 	if (active && mutex)
 		mutex->unlock();
 	*/
@@ -81,4 +151,7 @@ void AudioDriverJavaScript::finish() {
 }
 
 AudioDriverJavaScript::AudioDriverJavaScript() {
+
+	mix_rate = 44100;
+	singleton_js = this;
 }
diff --git a/platform/javascript/audio_driver_javascript.h b/platform/javascript/audio_driver_javascript.h
index c5cebe800f..c3adeca07b 100644
--- a/platform/javascript/audio_driver_javascript.h
+++ b/platform/javascript/audio_driver_javascript.h
@@ -35,7 +35,23 @@
 #include "os/mutex.h"
 
 class AudioDriverJavaScript : public AudioDriver {
+
+	enum {
+		INTERNAL_BUFFER_SIZE = 4096,
+		STREAM_SCALE_BITS = 12
+
+	};
+
+	int mix_rate;
+	float *internal_buffer;
+	int internal_buffer_channels;
+	int internal_buffer_size;
+	int32_t *stream_buffer;
+
 public:
+	void mix_to_js(int p_frames);
+	static AudioDriverJavaScript *singleton_js;
+
 	virtual const char *get_name() const;
 
 	virtual Error init();