Bug 1627818 - part1 : allow DecodedStream to notify audible state change. r=padenot

`AudioSink` provides a way to let us know if the media data is audible, and we should do the same thing for the `DecodedStream`, in order to update the correct audible state.

Differential Revision: https://phabricator.services.mozilla.com/D70259

dom/media/MediaDecoderStateMachine.cpp

@@ -2734,6 +2734,15 @@ void MediaDecoderStateMachine::AudioAudibleChanged(bool aAudible) {
 }
 
 MediaSink* MediaDecoderStateMachine::CreateAudioSink() {
+  if (mOutputCaptured) {
+    DecodedStream* stream =
+        new DecodedStream(this, mOutputTracks, mVolume, mPlaybackRate,
+                          mPreservesPitch, mAudioQueue, mVideoQueue);
+    mAudibleListener = stream->AudibleEvent().Connect(
+        OwnerThread(), this, &MediaDecoderStateMachine::AudioAudibleChanged);
+    return stream;
+  }
+
   RefPtr<MediaDecoderStateMachine> self = this;
   auto audioSinkCreator = [self]() {
     MOZ_ASSERT(self->OnTaskQueue());
@@ -2752,12 +2761,7 @@ MediaSink* MediaDecoderStateMachine::CreateAudioSink() {
 
 already_AddRefed<MediaSink> MediaDecoderStateMachine::CreateMediaSink() {
   MOZ_ASSERT(OnTaskQueue());
-  RefPtr<MediaSink> audioSink =
-      mOutputCaptured
-          ? new DecodedStream(this, mOutputTracks, mVolume, mPlaybackRate,
-                              mPreservesPitch, mAudioQueue, mVideoQueue)
-          : CreateAudioSink();
-
+  RefPtr<MediaSink> audioSink = CreateAudioSink();
   RefPtr<MediaSink> mediaSink =
       new VideoSink(mTaskQueue, audioSink, mVideoQueue, mVideoFrameContainer,
                     *mFrameStats, sVideoQueueSendToCompositorSize);
@@ -3113,12 +3117,11 @@ void MediaDecoderStateMachine::StopMediaSink() {
   MOZ_ASSERT(OnTaskQueue());
   if (mMediaSink->IsStarted()) {
     LOG("Stop MediaSink");
-    mAudibleListener.DisconnectIfExists();
-
     mMediaSink->Stop();
     mMediaSinkAudioEndedPromise.DisconnectIfExists();
     mMediaSinkVideoEndedPromise.DisconnectIfExists();
   }
+  mAudibleListener.DisconnectIfExists();
 }
 
 void MediaDecoderStateMachine::RequestAudioData() {

dom/media/mediasink/DecodedStream.cpp

@@ -654,6 +654,7 @@ void DecodedStream::SendAudio(double aVolume,
     LOG_DS(LogLevel::Verbose, "Queueing audio [%" PRId64 ",%" PRId64 "]",
            audio[i]->mTime.ToMicroseconds(),
            audio[i]->GetEndTime().ToMicroseconds());
+    CheckIsDataAudible(audio[i]);
     SendStreamAudio(mData.get(), mStartTime.ref(), audio[i], &output, rate,
                     aPrincipalHandle);
   }
@@ -670,6 +671,16 @@ void DecodedStream::SendAudio(double aVolume,
   }
 }
 
+void DecodedStream::CheckIsDataAudible(const AudioData* aData) {
+  MOZ_ASSERT(aData);
+
+  bool isAudible = aData->IsAudible();
+  if (isAudible != mIsAudioDataAudible) {
+    mIsAudioDataAudible = isAudible;
+    mAudibleEvent.Notify(mIsAudioDataAudible);
+  }
+}
+
 void DecodedStreamData::WriteVideoToSegment(
     layers::Image* aImage, const TimeUnit& aStart, const TimeUnit& aEnd,
     const gfx::IntSize& aIntrinsicSize, const TimeStamp& aTimeStamp,

dom/media/mediasink/DecodedStream.h

@@ -63,6 +63,8 @@ class DecodedStream : public MediaSink {
   void Shutdown() override;
   void GetDebugInfo(dom::MediaSinkDebugInfo& aInfo) override;
 
+  MediaEventSource<bool>& AudibleEvent() { return mAudibleEvent; }
+
  protected:
   virtual ~DecodedStream();
 
@@ -74,6 +76,7 @@ class DecodedStream : public MediaSink {
   void ResetVideo(const PrincipalHandle& aPrincipalHandle);
   void SendData();
   void NotifyOutput(int64_t aTime);
+  void CheckIsDataAudible(const AudioData* aData);
 
   void AssertOwnerThread() const {
     MOZ_ASSERT(mOwnerThread->IsCurrentThreadIn());
@@ -106,6 +109,9 @@ class DecodedStream : public MediaSink {
   media::NullableTimeUnit mStartTime;
   media::TimeUnit mLastOutputTime;
   MediaInfo mInfo;
+  // True when stream is producing audible sound, false when stream is silent.
+  bool mIsAudioDataAudible = false;
+  MediaEventProducer<bool> mAudibleEvent;
 
   MediaQueue<AudioData>& mAudioQueue;
   MediaQueue<VideoData>& mVideoQueue;