Allow media track switching.

media/renderers/audio_renderer_impl.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.
 
 // Audio rendering unit utilizing an AudioRendererSink to output data.
 //
 // This class lives inside three threads during it's lifetime, namely:
 // 1. Render thread
 //    Where the object is created.
 // 2. Media thread (provided via constructor)
@@ skipping 18 matching lines @@
 #include "base/power_monitor/power_observer.h"
 #include "base/synchronization/lock.h"
 #include "media/base/audio_decoder.h"
 #include "media/base/audio_renderer.h"
 #include "media/base/audio_renderer_sink.h"
 #include "media/base/decryptor.h"
 #include "media/base/media_log.h"
 #include "media/base/time_source.h"
 #include "media/filters/audio_renderer_algorithm.h"
 #include "media/filters/decoder_stream.h"
+#include "media/renderers/default_renderer_factory.h"
 
 namespace base {
 class SingleThreadTaskRunner;
 class TickClock;
 }
 
 namespace media {
 
 class AudioBufferConverter;
 class AudioBus;
 class AudioClock;
 
 class MEDIA_EXPORT AudioRendererImpl
     : public AudioRenderer,
       public TimeSource,
       public base::PowerObserver,
       NON_EXPORTED_BASE(public AudioRendererSink::RenderCallback) {
  public:
   // |task_runner| is the thread on which AudioRendererImpl will execute.
   //
   // |sink| is used as the destination for the rendered audio.
   //
   // |decoders| contains the AudioDecoders to use when initializing.
   AudioRendererImpl(
       const scoped_refptr<base::SingleThreadTaskRunner>& task_runner,
       AudioRendererSink* sink,
-      ScopedVector<AudioDecoder> decoders,
+      const CreateAudioDecodersCB& create_audio_decoders_cb,
       const scoped_refptr<MediaLog>& media_log);
   ~AudioRendererImpl() override;
 
   // TimeSource implementation.
   void StartTicking() override;
   void StopTicking() override;
   void SetPlaybackRate(double rate) override;
   void SetMediaTime(base::TimeDelta time) override;
   base::TimeDelta CurrentMediaTime() override;
   bool GetWallClockTimes(
@@ skipping 13 matching lines @@
   // base::PowerObserver implementation.
   void OnSuspend() override;
   void OnResume() override;
 
  private:
   friend class AudioRendererImplTest;
 
   // Important detail: being in kPlaying doesn't imply that audio is being
   // rendered. Rather, it means that the renderer is ready to go. The actual
   // rendering of audio is controlled via Start/StopRendering().
+  // Audio renderer can be reinitialized completely by calling Initialize again
+  // when it is in a kFlushed and stopped (StopTicking) state.

[xhwang, 2017/03/22 22:31:12]

Please update AudioRenderer interface documentation about when Initialize() can
be called.

[servolk, 2017/03/23 17:08:10]

Done.

   //
   //   kUninitialized
-  //         | Initialize()
-  //         |
-  //         V
-  //    kInitializing
-  //         | Decoders initialized
-  //         |
-  //         V            Decoders reset
-  //      kFlushed <------------------ kFlushing
+  //  +----> | Initialize()
+  //  |      |
+  //  |      V
+  //  | kInitializing
+  //  |      | Decoders initialized
+  //  |      |
+  //  |      V            Decoders reset
+  //  +-  kFlushed <------------------ kFlushing
   //         | StartPlaying()             ^
   //         |                            |
   //         |                            | Flush()
   //         `---------> kPlaying --------'
   enum State {
     kUninitialized,
     kInitializing,
     kFlushing,
     kFlushed,
     kPlaying
@@ skipping 127 matching lines @@
   // under |lock_|. ------------------------------------------------------------
   base::Lock lock_;
 
   // Algorithm for scaling audio.
   double playback_rate_;
   std::unique_ptr<AudioRendererAlgorithm> algorithm_;
 
   // Simple state tracking variable.
   State state_;
 
+  CreateAudioDecodersCB create_audio_decoders_cb_;
+
   BufferingState buffering_state_;
 
   // Keep track of whether or not the sink is playing and whether we should be
   // rendering.
   bool rendering_;
   bool sink_playing_;
 
   // Keep track of our outstanding read to |decoder_|.
   bool pending_read_;
 
@@ skipping 32 matching lines @@
 
   // NOTE: Weak pointers must be invalidated before all other member variables.
   base::WeakPtrFactory<AudioRendererImpl> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioRendererImpl);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_RENDERERS_AUDIO_RENDERER_IMPL_H_