Fix an issue that audio and video may run out of sync

media/base/android/audio_decoder_job.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/base/android/audio_decoder_job.h"
 
 #include "base/bind.h"
 #include "base/lazy_instance.h"
 #include "base/threading/thread.h"
 #include "media/base/android/media_codec_bridge.h"
+#include "media/base/audio_timestamp_helper.h"
+
+namespace {
+
+// Use 16bit PCM for audio output. Keep this value in sync with the output
+// format we passed to AudioTrack in MediaCodecBridge.
+const int kBytesPerAudioOutputSample = 2;
+}
 
 namespace media {
 
 class AudioDecoderThread : public base::Thread {
  public:
   AudioDecoderThread() : base::Thread("MediaSource_AudioDecoderThread") {
     Start();
   }
 };
 
 // TODO(qinmin): Check if it is tolerable to use worker pool to handle all the
 // decoding tasks so that we don't need a global thread here.
 // http://crbug.com/245750
 base::LazyInstance<AudioDecoderThread>::Leaky
     g_audio_decoder_thread = LAZY_INSTANCE_INITIALIZER;
 
 AudioDecoderJob* AudioDecoderJob::Create(
     const AudioCodec audio_codec,
     int sample_rate,
     int channel_count,
     const uint8* extra_data,
     size_t extra_data_size,
     jobject media_crypto,
     const base::Closure& request_data_cb) {
   scoped_ptr<AudioCodecBridge> codec(AudioCodecBridge::Create(audio_codec));
   if (codec && codec->Start(audio_codec, sample_rate, channel_count, extra_data,
                             extra_data_size, true, media_crypto)) {
-    return new AudioDecoderJob(codec.Pass(), request_data_cb);
+    scoped_ptr<AudioTimestampHelper> audio_timestamp_helper(
+        new AudioTimestampHelper(sample_rate));
+    return new AudioDecoderJob(
+        audio_timestamp_helper.Pass(), codec.Pass(),
+        kBytesPerAudioOutputSample * channel_count, request_data_cb);
   }
-
   LOG(ERROR) << "Failed to create AudioDecoderJob.";
   return NULL;
 }
 
 AudioDecoderJob::AudioDecoderJob(
+    scoped_ptr<AudioTimestampHelper> audio_timestamp_helper,
     scoped_ptr<AudioCodecBridge> audio_codec_bridge,
+    int bytes_per_frame,
     const base::Closure& request_data_cb)
     : MediaDecoderJob(g_audio_decoder_thread.Pointer()->message_loop_proxy(),
                       audio_codec_bridge.get(), request_data_cb),
-      audio_codec_bridge_(audio_codec_bridge.Pass()) {
+      bytes_per_frame_(bytes_per_frame),
+      audio_codec_bridge_(audio_codec_bridge.Pass()),
+      audio_timestamp_helper_(audio_timestamp_helper.Pass()) {
 }
 
 AudioDecoderJob::~AudioDecoderJob() {
 }
 
 void AudioDecoderJob::SetVolume(double volume) {
   audio_codec_bridge_->SetVolume(volume);
 }
 
+void AudioDecoderJob::SetBaseTimestamp(base::TimeDelta base_timestamp) {
+  audio_timestamp_helper_->SetBaseTimestamp(base_timestamp);
+}
+
 void AudioDecoderJob::ReleaseOutputBuffer(
     int output_buffer_index,
     size_t size,
     bool render_output,
+    base::TimeDelta current_presentation_timestamp,
     const ReleaseOutputCompletionCallback& callback) {
-  size_t size_to_render = render_output ? size : 0u;
-  if (size_to_render)
-    audio_codec_bridge_->PlayOutputBuffer(output_buffer_index, size_to_render);
+  render_output = render_output && (size != 0u);
+  if (render_output) {
+    int64 head_position = audio_codec_bridge_->PlayOutputBuffer(
+        output_buffer_index, size);
+    audio_timestamp_helper_->AddFrames(size / (bytes_per_frame_));
+    int64 frames_to_play =
+        audio_timestamp_helper_->frame_count() - head_position;
+    DCHECK_GE(frames_to_play, 0);
+    current_presentation_timestamp =
+        audio_timestamp_helper_->GetTimestamp() -
+        audio_timestamp_helper_->GetFrameDuration(frames_to_play);
+  } else {
+    current_presentation_timestamp = kNoTimestamp();
+  }
   audio_codec_bridge_->ReleaseOutputBuffer(output_buffer_index, false);
-
-  callback.Run(size_to_render);
+  callback.Run(current_presentation_timestamp,
+               audio_timestamp_helper_->GetTimestamp());
 }
 
 bool AudioDecoderJob::ComputeTimeToRender() const {
   return false;
 }
 
 }  // namespace media