Update WebmMuxer for audio component of MediaStream recording.

media/capture/webm_muxer.h

Index: media/capture/webm_muxer.h
diff --git a/media/capture/webm_muxer.h b/media/capture/webm_muxer.h
index 7196d1d4f9f33c95b88548ab8ba92dd3589015c1..a68b68562ab27275ddf3fd4ab0e1d4b73373daf4 100644
--- a/media/capture/webm_muxer.h
+++ b/media/capture/webm_muxer.h
@@ -21,18 +21,20 @@ class Size;
 namespace media {
 
 class VideoFrame;
+class AudioParameters;
 
 // Adapter class to manage a WebM container [1], a simplified version of a
 // Matroska container [2], composed of an EBML header, and a single Segment
 // including at least a Track Section and a number of SimpleBlocks each
-// containing a single encoded video frame. WebM container has no Trailer.
-// Clients will push encoded VPx video frames one by one via OnEncodedVideo().
-// libwebm will eventually ping the WriteDataCB passed on contructor with the
+// containing a single encoded video or audio frame. WebM container has no
+// Trailer.
+// Clients will push encoded VPx video frames and Opus audio frames one by one
+// via OnEncoded{Video|Audio}(). libwebm will eventually ping the WriteDataCB
+// passed on contructor with the

[mcasas, 2015/11/06 02:22:37]

Reflow l.33-34

[ajose, 2015/11/06 18:40:52]

Done.

 // wrapped encoded data.
-// WebmMuxer is designed for single thread use throughout.
+// WebmMuxer is designed for use on a single thread.
 // [1] http://www.webmproject.org/docs/container/
 // [2] http://www.matroska.org/technical/specs/index.html
-// TODO(mcasas): Add support for Audio muxing.
 class MEDIA_EXPORT WebmMuxer : public NON_EXPORTED_BASE(mkvmuxer::IMkvWriter) {
  public:
   // Callback to be called when WebmMuxer is ready to write a chunk of data,
@@ -41,23 +43,32 @@ class MEDIA_EXPORT WebmMuxer : public NON_EXPORTED_BASE(mkvmuxer::IMkvWriter) {
 
   // |codec| can be VP8 or VP9 and should coincide with whatever is sent in
   // OnEncodedVideo().
-  WebmMuxer(VideoCodec codec, const WriteDataCB& write_data_callback);
+  WebmMuxer(VideoCodec codec,
+            uint8_t num_video_tracks,
+            uint8_t num_audio_tracks,
+            const WriteDataCB& write_data_callback);
   ~WebmMuxer() override;
 
-  // Adds a |video_frame| with |encoded_data.data()| to WebM Segment.
+  // Functions to add video and audio frames with |encoded_data.data()|
+  // to WebM Segment.
   void OnEncodedVideo(const scoped_refptr<VideoFrame>& video_frame,
                       scoped_ptr<std::string> encoded_data,
                       base::TimeTicks timestamp,
                       bool is_key_frame);
+  void OnEncodedAudio(const media::AudioParameters& params,
+                      scoped_ptr<std::string> encoded_data,
+                      base::TimeTicks timestamp);
 
  private:
   friend class WebmMuxerTest;
 
-  // Creates and adds a new video track. Called upon receiving the first
-  // frame of a given Track, adds |frame_size| and |frame_rate| to the Segment
+  // Methods for creating and adding video and audio tracks, called upon
+  // receiving the first frame of a given Track.
+  // AddVideoTrack adds |frame_size| and |frame_rate| to the Segment
   // info, although individual frames passed to OnEncodedVideo() can have any
   // frame size.
   void AddVideoTrack(const gfx::Size& frame_size, double frame_rate);
+  void AddAudioTrack(const media::AudioParameters& params);
 
   // IMkvWriter interface.
   mkvmuxer::int32 Write(const void* buf, mkvmuxer::uint32 len) override;
@@ -73,12 +84,18 @@ class MEDIA_EXPORT WebmMuxer : public NON_EXPORTED_BASE(mkvmuxer::IMkvWriter) {
   // Video Codec configured: VP9 if true, otherwise VP8 is used by default.
   const bool use_vp9_;
 
-  // A caller-side identifier to interact with |segment_|, initialised upon
-  // first frame arrival by AddVideoTrack().
-  uint64_t track_index_;
+  // Caller-side identifiers to interact with |segment_|, initialised upon
+  // first frame arrival to Add{Video, Audio}Track().
+  uint8_t video_track_index_;
+  uint8_t audio_track_index_;
 
   // Origin of times for frame timestamps.
   base::TimeTicks first_frame_timestamp_;
+  base::TimeDelta most_recent_timestamp_;
+
+  // The expected total number of video and audio tracks.
+  const uint8_t num_video_tracks_;
+  const uint8_t num_audio_tracks_;

[mcasas, 2015/11/06 02:22:37]

Since for this CL we don't support
|num_video_tracks_| > 1 or |num_audio_tracks_| > 1,
I'd say 
a) remove the members and associated checks
b) leave a TODO in the class if you want (with bug of course)
c) remove the associate constructor params.

IOW remove all the multi-track parts from this CL if
they are not used on ToT :)

On a parallel discussion, I see the utility of supporting
several audio tracks (e.g. stereo or 5:1 audio) but it
might not be too urgent to support several video tracks,
as a matter of fact I've never seen a MediaStream with
more than a video tracks. Even more, have you ever
seen a .webm file with >1 video track? How would we
play it back...?

[ajose, 2015/11/06 18:40:52]

Done.

 
   // Callback to dump written data as being called by libwebm.
   const WriteDataCB write_data_callback_;