Bug 1171311: P10. Add MediaDataDemuxer::GetSamplesMayBlock() method. r=cpearce

This is used by the MediaFormatReader to dermine if buffering heuristics should
be used.

--HG--
extra : rebase_source : 49d67f021ce8660cd67a12510e5c631d6b96698a

dom/media/MediaDataDemuxer.h

@@ -156,6 +156,15 @@ public:
   // sample will contains multiple audio frames.
   virtual nsRefPtr<SamplesPromise> GetSamples(int32_t aNumSamples = 1) = 0;
 
+  // Returns true if a call to GetSamples() may block while waiting on the
+  // underlying resource to return the data.
+  // This is used by the MediaFormatReader to determine if buffering heuristics
+  // should be used.
+  virtual bool GetSamplesMayBlock() const
+  {
+    return true;
+  }
+
   // Cancel all pending actions (Seek, GetSamples) and reset current state
   // All pending promises are to be rejected with CANCEL.
   // The next call to GetSamples would return the first sample available in the

dom/media/MediaFormatReader.cpp

@@ -72,6 +72,7 @@ MediaFormatReader::MediaFormatReader(AbstractMediaDecoder* aDecoder,
   , mInitDone(false)
   , mSeekable(false)
   , mIsEncrypted(false)
+  , mTrackDemuxersMayBlock(false)
   , mCachedTimeRangesStale(true)
 #if defined(READER_DORMANT_HEURISTIC)
   , mDormantEnabled(Preferences::GetBool("media.decoder.heuristic.dormant.enabled", false))
@@ -304,6 +305,7 @@ MediaFormatReader::OnDemuxerInitDone(nsresult)
     mInfo.mVideo = *mVideo.mTrackDemuxer->GetInfo()->GetAsVideoInfo();
     mVideo.mCallback = new DecoderCallback(this, TrackInfo::kVideoTrack);
     mVideo.mTimeRanges = mVideo.mTrackDemuxer->GetBuffered();
+    mTrackDemuxersMayBlock |= mVideo.mTrackDemuxer->GetSamplesMayBlock();
   }
 
   bool audioActive = !!mDemuxer->GetNumberTracks(TrackInfo::kAudioTrack);
@@ -313,6 +315,7 @@ MediaFormatReader::OnDemuxerInitDone(nsresult)
     mInfo.mAudio = *mAudio.mTrackDemuxer->GetInfo()->GetAsAudioInfo();
     mAudio.mCallback = new DecoderCallback(this, TrackInfo::kAudioTrack);
     mAudio.mTimeRanges = mAudio.mTrackDemuxer->GetBuffered();
+    mTrackDemuxersMayBlock |= mAudio.mTrackDemuxer->GetSamplesMayBlock();
   }
 
   UniquePtr<EncryptionInfo> crypto = mDemuxer->GetCrypto();

dom/media/MediaFormatReader.h

@@ -99,6 +99,11 @@ public:
 
   int64_t ComputeStartTime(const VideoData* aVideo, const AudioData* aAudio) override;
 
+  bool UseBufferingHeuristics() override
+  {
+    return mTrackDemuxersMayBlock;
+  }
+
 private:
   bool InitDemuxer();
   // Notify the demuxer that new data has been received.
@@ -366,6 +371,9 @@ private:
   // become incorrect.
   bool mIsEncrypted;
 
+  // Set to true if any of our track buffers may be blocking.
+  bool mTrackDemuxersMayBlock;
+
   // Seeking objects.
   bool IsSeeking() const { return mPendingSeekTime.isSome(); }
   void AttemptSeek();

dom/media/mediasource/MediaSourceDemuxer.h

@@ -107,6 +107,11 @@ public:
 
   void BreakCycles() override;
 
+  bool GetSamplesMayBlock() const override
+  {
+    return false;
+  }
+
   // Called by TrackBuffersManager to indicate that new frames were added or
   // removed.
   void NotifyTimeRangesChanged();