Allow audio system to handle synchronized low-latency audio I/O

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 62 matching lines @@
 namespace media {
 
 class MEDIA_EXPORT AudioOutputDevice
     : NON_EXPORTED_BASE(public AudioRendererSink),
       public AudioOutputIPCDelegate,
       NON_EXPORTED_BASE(public ScopedLoopObserver) {
  public:
   // AudioRendererSink implementation.
   virtual void Initialize(const AudioParameters& params,
                           RenderCallback* callback) OVERRIDE;
+  virtual void InitializeIO(const AudioParameters& params,
+                            int input_channels,
+                            RenderCallback* callback) OVERRIDE;
   virtual void Start() OVERRIDE;
   virtual void Stop() OVERRIDE;
   virtual void Play() OVERRIDE;
   virtual void Pause(bool flush) OVERRIDE;
   virtual bool SetVolume(double volume) OVERRIDE;
 
   // Methods called on IO thread ----------------------------------------------
   // AudioOutputIPCDelegate methods.
   virtual void OnStateChanged(AudioOutputIPCDelegate::State state) OVERRIDE;
   virtual void OnStreamCreated(base::SharedMemoryHandle handle,
@@ skipping 12 matching lines @@
   // Magic required by ref_counted.h to avoid any code deleting the object
   // accidentally while there are references to it.
   friend class base::RefCountedThreadSafe<AudioOutputDevice>;
   virtual ~AudioOutputDevice();
 
  private:
   // Methods called on IO thread ----------------------------------------------
   // The following methods are tasks posted on the IO thread that needs to
   // be executed on that thread. They interact with AudioMessageFilter and
   // sends IPC messages on that thread.
-  void CreateStreamOnIOThread(const AudioParameters& params);
+  void CreateStreamOnIOThread(const AudioParameters& params,
+                              int input_channels);
   void PlayOnIOThread();
   void PauseOnIOThread(bool flush);
   void ShutDownOnIOThread();
   void SetVolumeOnIOThread(double volume);
 
   // MessageLoop::DestructionObserver implementation for the IO loop.
   // If the IO loop dies before we do, we shut down the audio thread from here.
   virtual void WillDestroyCurrentMessageLoop() OVERRIDE;
 
   AudioParameters audio_parameters_;
 
+  // The number of optional synchronized input channels having the same
+  // sample-rate and buffer-size as specified in audio_parameters_.
+  int input_channels_;
+
   RenderCallback* callback_;
 
   // A pointer to the IPC layer that takes care of sending requests over to
   // the AudioRendererHost.
   AudioOutputIPC* ipc_;
 
   // Our stream ID on the message filter. Only accessed on the IO thread.
   // Must only be modified on the IO thread.
   int stream_id_;
 
@@ skipping 15 matching lines @@
   AudioDeviceThread audio_thread_;
   scoped_ptr<AudioOutputDevice::AudioThreadCallback> audio_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioOutputDevice);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_AUDIO_OUTPUT_DEVICE_H_