Allow muting/unmuting audio through media track API

media/filters/chunk_demuxer.h

 // Copyright (c) 2012 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.
 
 #ifndef MEDIA_FILTERS_CHUNK_DEMUXER_H_
 #define MEDIA_FILTERS_CHUNK_DEMUXER_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 190 matching lines @@
   // kReachedIdLimit is returned if the demuxer cannot handle another ID right
   //    now.
   Status AddId(const std::string& id, const std::string& type,
                std::vector<std::string>& codecs);
 
   // Notifies a caller via |tracks_updated_cb| that the set of media tracks
   // for a given |id| has changed.
   void SetTracksWatcher(const std::string& id,
                         const MediaTracksUpdatedCB& tracks_updated_cb);
 
+  // Notifies the demuxer that a track id has been assigned to a media track.
+  // If |track| is null the association for this |track_id| is removed.

[wolenetz, 2016/03/30 00:31:32]

who owns the memory pointed to by |track|?

[servolk, 2016/03/30 01:13:13]

It doesn't matter, because we don't actually care about the MediaTrack lifetime
here. We don't even need it to be alive! I'm essentially just using the pointer
value as a unique track id here, which will allow us to establish mapping from
blink trackId -> MediaTrack* -> DemuxerStream*. And then we pass the
DemuxerStream* pointer values to media::Renderer. We never access the pointee
objects, so they don't need to be alive. When media::Renderer receives the
DemuxerStream*, it can use it as an identifier that points to some DemuxerStream
and media::Renderer knows about DemuxerStreams, so then the RendererImpl can
check that the given DemuxerStream* pointers are valid and alive.

[wolenetz, 2016/03/30 20:15:55]

Hmm. Using a pointer just as an ID is not clear and risks future incorrect
dereferencing. Please try a better way to identify uniquely the Chromium
MediaTrack in these (persistent) mappings that may survive beyond the life of
the Chromium MediaTrack.

+  void OnTrackIdAssigned(unsigned track_id, const MediaTrack* track) override;
+
+  // Finds a DemuxerStream corresponding to the given blink |track_id|. Note
+  // that the input track id is blink track id and not bytestream track id.
+  const DemuxerStream* GetDemuxerStreamByTrackId(
+      unsigned track_id) const override;
+
   // Removed an ID & associated resources that were previously added with
   // AddId().
   void RemoveId(const std::string& id);
 
   // Gets the currently buffered ranges for the specified ID.
   Ranges<base::TimeDelta> GetBufferedRanges(const std::string& id) const;
 
   // Appends media data to the source buffer associated with |id|, applying
   // and possibly updating |*timestamp_offset| during coded frame processing.
   // |append_window_start| and |append_window_end| correspond to the MSE spec's
@@ skipping 90 matching lines @@
   // Returns true if any stream has seeked to a time without buffered data.
   bool IsSeekWaitingForData_Locked() const;
 
   // Returns true if all streams can successfully call EndOfStream,
   // false if any can not.
   bool CanEndOfStream_Locked() const;
 
   // MediaSourceState callbacks.
   void OnSourceInitDone(const StreamParser::InitParameters& params);
 
-  // Creates a DemuxerStream for the specified |type|.
+  // Creates a DemuxerStream for the specified |media_track|.
   // Returns a new ChunkDemuxerStream instance if a stream of this type
   // has not been created before. Returns NULL otherwise.
-  ChunkDemuxerStream* CreateDemuxerStream(DemuxerStream::Type type);
+  ChunkDemuxerStream* CreateDemuxerStream(const MediaTrack& media_track);
 
   void OnNewTextTrack(ChunkDemuxerStream* text_stream,
                       const TextTrackConfig& config);
 
   // Returns true if |source_id| is valid, false otherwise.
   bool IsValidId(const std::string& source_id) const;
 
   // Increases |duration_| to |new_duration|, if |new_duration| is higher.
   void IncreaseDurationIfNecessary(base::TimeDelta new_duration);
 
@@ skipping 39 matching lines @@
   PipelineStatusCB init_cb_;
   // Callback to execute upon seek completion.
   // TODO(wolenetz/acolwell): Protect against possible double-locking by first
   // releasing |lock_| before executing this callback. See
   // http://crbug.com/308226
   PipelineStatusCB seek_cb_;
 
   scoped_ptr<ChunkDemuxerStream> audio_;
   scoped_ptr<ChunkDemuxerStream> video_;
 
+  std::map<unsigned, const MediaTrack*> track_id_to_track_map_;
+  std::map<const MediaTrack*, const DemuxerStream*> track_to_stream_map_;
+
   base::TimeDelta duration_;
 
   // The duration passed to the last SetDuration(). If
   // SetDuration() is never called or an AppendData() call or
   // a EndOfStream() call changes |duration_|, then this
   // variable is set to < 0 to indicate that the |duration_| represents
   // the actual duration instead of a user specified value.
   double user_specified_duration_;
 
   base::Time timeline_offset_;
@@ skipping 10 matching lines @@
 
   // Indicates that splice frame generation is enabled.
   const bool splice_frames_enabled_;
 
   DISALLOW_COPY_AND_ASSIGN(ChunkDemuxer);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_FILTERS_CHUNK_DEMUXER_H_