Allow media track switching.

media/renderers/renderer_impl.h

 // Copyright 2014 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_RENDERERS_RENDERER_IMPL_H_
 #define MEDIA_RENDERERS_RENDERER_IMPL_H_
 
 #include <list>
 #include <memory>
 #include <vector>
@@ skipping 45 matching lines @@
   void SetCdm(CdmContext* cdm_context,
               const CdmAttachedCB& cdm_attached_cb) final;
   void Flush(const base::Closure& flush_cb) final;
   void StartPlayingFrom(base::TimeDelta time) final;
   void SetPlaybackRate(double playback_rate) final;
   void SetVolume(float volume) final;
   base::TimeDelta GetMediaTime() final;
 
   void OnStreamStatusChanged(DemuxerStream* stream,
                              bool enabled,
                              base::TimeDelta time);

[xhwang, 2017/03/29 00:16:47]

This doesn't need to be public. Also it would be nice to be grouped together
with other stream-switching functions, e.g. Reinitialize*Renderer().

[servolk, 2017/03/29 01:49:33]

Done.

 
   // Helper functions for testing purposes. Must be called before Initialize().
   void DisableUnderflowForTesting();
   void EnableClocklessVideoPlaybackForTesting();
   void set_time_source_for_testing(TimeSource* time_source) {
     time_source_ = time_source;
   }
   void set_video_underflow_threshold_for_testing(base::TimeDelta threshold) {
     video_underflow_threshold_ = threshold;
   }
@@ skipping 22 matching lines @@
   void OnAudioRendererInitializeDone(PipelineStatus status);
   void InitializeVideoRenderer();
   void OnVideoRendererInitializeDone(PipelineStatus status);
 
   // Helper functions and callbacks for Flush().
   void FlushAudioRenderer();
   void OnAudioRendererFlushDone();
   void FlushVideoRenderer();
   void OnVideoRendererFlushDone();
 
-  void RestartAudioRenderer(base::TimeDelta time);
-  void RestartVideoRenderer(base::TimeDelta time);
+  // Reinitialize audio/video renderer during a media track switching. The
+  // renderer must be flushed first, and when the re-init is completed the
+  // corresponding callback will be invoked to restart playback.
+  // The |stream| parameter specifies the demuxer stream representing the new
+  // media track. And the |time| parameter specifies the time on media timeline
+  // where the switch occured.

[xhwang, 2017/03/29 00:16:47]

nit: At this level, we are dealing with DemuxerStream swiching (StatusChange)
and we don't need to mention "media track". People looking at this code would
have no idea what a media track is.

[servolk, 2017/03/29 01:49:33]

Done.

+  void ReinitializeAudioRenderer(DemuxerStream* stream, base::TimeDelta time);
+  void OnAudioRendererReinitialized(DemuxerStream* stream,
+                                    base::TimeDelta time,
+                                    PipelineStatus status);
+  void ReinitializeVideoRenderer(DemuxerStream* stream, base::TimeDelta time);
+  void OnVideoRendererReinitialized(DemuxerStream* stream,
+                                    base::TimeDelta time,
+                                    PipelineStatus status);
+
+  // Restart audio/video renderer playback after a media track switch or after a
+  // media track has been disabled and re-enabled. The |stream| parameter

[xhwang, 2017/03/29 00:16:47]

ditto about "media track"

[servolk, 2017/03/29 01:49:33]

Done.

+  // specifies which stream needs to be restarted. The |time| parameter
+  // specifies the position on the media timeline where the playback needs to be
+  // restarted. It is necessary for demuxers with independent streams (e.g. MSE
+  // / ChunkDemuxer) to synchronize data reading between those streams.
+  void RestartAudioRenderer(DemuxerStream* stream, base::TimeDelta time);
+  void RestartVideoRenderer(DemuxerStream* stream, base::TimeDelta time);
 
   // Callback executed by filters to update statistics.
   void OnStatisticsUpdate(const PipelineStatistics& stats);
 
   // Collection of callback methods and helpers for tracking changes in
   // buffering state and transition from paused/underflow states and playing
   // states.
   //
   // While in the kPlaying state:
   //   - A waiting to non-waiting transition indicates preroll has completed
   //     and StartPlayback() should be called
   //   - A non-waiting to waiting transition indicates underflow has occurred
   //     and PausePlayback() should be called
   void OnBufferingStateChange(DemuxerStream::Type type,
                               BufferingState new_buffering_state);

[xhwang, 2017/03/29 00:16:47]

empty line

[servolk, 2017/03/29 01:49:33]

Done.

   // Handles the buffering notifications that we might get while an audio or a
   // video stream is being restarted. In those cases we don't want to report
   // underflows immediately and instead give decoders a chance to catch up with
   // currently playing stream. Returns true if the buffering nofication has been
   // handled and no further processing is necessary, returns false to indicate
   // that we should fall back to the regular OnBufferingStateChange logic.
   bool HandleRestartedStreamBufferingChanges(
       DemuxerStream::Type type,
       BufferingState new_buffering_state);

[xhwang, 2017/03/29 00:16:47]

empty line

[servolk, 2017/03/29 01:49:33]

Done.

   bool WaitingForEnoughData() const;
   void PausePlayback();
   void StartPlayback();
 
   // Callbacks executed when a renderer has ended.
   void OnRendererEnded(DemuxerStream::Type type);
   bool PlaybackHasEnded() const;
   void RunEndedCallbackIfNeeded();
 
   // Callback executed when a runtime error happens.
@@ skipping 14 matching lines @@
 
   // Temporary callback used for Initialize() and Flush().
   PipelineStatusCB init_cb_;
   base::Closure flush_cb_;
 
   std::unique_ptr<RendererClientInternal> audio_renderer_client_;
   std::unique_ptr<RendererClientInternal> video_renderer_client_;
   std::unique_ptr<AudioRenderer> audio_renderer_;
   std::unique_ptr<VideoRenderer> video_renderer_;
 
+  DemuxerStream* current_audio_stream_;
+  DemuxerStream* current_video_stream_;
+
   // Renderer-provided time source used to control playback.
   TimeSource* time_source_;
   std::unique_ptr<WallClockTimeSource> wall_clock_time_source_;
   bool time_ticking_;
   double playback_rate_;
 
   // The time to start playback from after starting/seeking has completed.
   base::TimeDelta start_time_;
 
   BufferingState audio_buffering_state_;
@@ skipping 25 matching lines @@
 
   base::WeakPtr<RendererImpl> weak_this_;
   base::WeakPtrFactory<RendererImpl> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RendererImpl);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_RENDERERS_RENDERER_IMPL_H_