Making AudioThread::Thread restartable *** DRAFT ***

media/audio/audio_output_device.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 audio output stream provided by browser
 // process through IPC.
 //
 // Relationship of classes.
 //
 //  AudioOutputController                AudioOutputDevice
@@ skipping 26 matching lines @@
 // OnStreamCreated are deferred until OnStreamCreated, with the last valid
 // state being used)
 //
 // AudioOutputDevice::Render => audio transport on audio thread =>
 //                               |
 // Stop --> ShutDownOnIOThread -------->  CloseStream -> Close
 //
 // This class utilizes several threads during its lifetime, namely:
 // 1. Creating thread.
 //    Must be the main render thread.
 // 2. Control thread (may be the main render thread or another thread).

[Henrik Grunell, 2016/03/31 09:01:37]

Hmm, "Start(), Stop(), Play(), Pause(), SetVolume() must be called on the same
thread." But there are no thread checks. What about adding that?

[Henrik Grunell, 2016/05/09 12:13:37]

This comment is obsolete. For example, Pause() is called in the Render()
callback function in the mixer. Removed in other CL.

 //    The methods: Start(), Stop(), Play(), Pause(), SetVolume()
 //    must be called on the same thread.
 // 3. IO thread (internal implementation detail - not exposed to public API)
 //    The thread within which this class receives all the IPC messages and
 //    IPC communications can only happen in this thread.
 // 4. Audio transport thread (See AudioDeviceThread).
 //    Responsible for calling the AudioThreadCallback implementation that in
 //    turn calls AudioRendererSink::RenderCallback which feeds audio samples to
 //    the audio layer in the browser process using sync sockets and shared
 //    memory.
@@ skipping 15 matching lines @@
 #include "media/audio/audio_output_ipc.h"
 #include "media/audio/audio_parameters.h"
 #include "media/audio/scoped_task_runner_observer.h"
 #include "media/base/audio_renderer_sink.h"
 #include "media/base/media_export.h"
 #include "media/base/output_device.h"
 
 namespace media {
 
 class MEDIA_EXPORT AudioOutputDevice
-    : NON_EXPORTED_BASE(public AudioRendererSink),
+    : NON_EXPORTED_BASE(public RestartableAudioRendererSink),
       NON_EXPORTED_BASE(public AudioOutputIPCDelegate),
       NON_EXPORTED_BASE(public OutputDevice),
       NON_EXPORTED_BASE(public ScopedTaskRunnerObserver) {
  public:
   // NOTE: Clients must call Initialize() before using.
   AudioOutputDevice(
       scoped_ptr<AudioOutputIPC> ipc,
       const scoped_refptr<base::SingleThreadTaskRunner>& io_task_runner,
       int session_id,
       const std::string& device_id,
@@ skipping 47 matching lines @@
   // Unsupported OutputDevice implementation
   void SwitchOutputDevice(const std::string& device_id,
                           const url::Origin& security_origin,
                           const SwitchOutputDeviceCB& callback) override;
 
   // Methods called on IO thread ----------------------------------------------
   // The following methods are tasks posted on the IO thread that need to
   // be executed on that thread.  They use AudioOutputIPC to send IPC messages
   // upon state changes.
   void RequestDeviceAuthorizationOnIOThread();
-  void CreateStreamOnIOThread(const AudioParameters& params);
+  void InitializeOnIOThread(const AudioParameters& params,
+                            RenderCallback* callback);
+  void CreateStreamOnIOThread();
   void PlayOnIOThread();
   void PauseOnIOThread();
-  void ShutDownOnIOThread();
+  void StopOnIOThread();
   void SetVolumeOnIOThread(double volume);
 
   // base::MessageLoop::DestructionObserver implementation for the IO loop.
   // If the IO loop dies before we do, we shut down the audio thread from here.
   void WillDestroyCurrentMessageLoop() override;
 
   AudioParameters audio_parameters_;
 
   RenderCallback* callback_;
 
@@ skipping 40 matching lines @@
   base::WaitableEvent did_receive_auth_;
   media::AudioParameters output_params_;
   OutputDeviceStatus device_status_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioOutputDevice);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_AUDIO_OUTPUT_DEVICE_H_