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

media/audio/audio_output_ipc.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_AUDIO_AUDIO_OUTPUT_IPC_H_
 #define MEDIA_AUDIO_AUDIO_OUTPUT_IPC_H_
 
 #include "base/shared_memory.h"
 #include "base/sync_socket.h"
 #include "media/audio/audio_parameters.h"
@@ skipping 50 matching lines @@
   // be used with all other IPC functions in this interface.
   virtual int AddDelegate(AudioOutputIPCDelegate* delegate) = 0;
 
   // Unregisters a delegate that was previously registered via a call to
   // AddDelegate().  The audio stream should be in a closed state prior to
   // calling this function.
   virtual void RemoveDelegate(int stream_id) = 0;
 
   // Sends a request to create an AudioOutputController object in the peer
   // process, identify it by |stream_id| and configure it to use the specified
-  // audio |params|.  Once the stream has been created, the implementation must
+  // audio |params| and number of synchronized input channels.
+  // Once the stream has been created, the implementation must
   // generate a notification to the AudioOutputIPCDelegate and call
   // OnStreamCreated().
-  virtual void CreateStream(int stream_id, const AudioParameters& params) = 0;
+  virtual void CreateStream(int stream_id,
+                            const AudioParameters& params,
+                            int input_channels) = 0;
 
   // Starts playing the stream.  This should generate a call to
   // AudioOutputController::Play().
   virtual void PlayStream(int stream_id) = 0;
 
   // Pauses an audio stream.  This should generate a call to
   // AudioOutputController::Pause().
   virtual void PauseStream(int stream_id) = 0;
 
   // "Flushes" the audio device. This should generate a call to
   // AudioOutputController::Flush().
   // TODO(tommi): This is currently neither implemented nor called.  Remove?
   virtual void FlushStream(int stream_id) = 0;
 
   // Closes the audio stream and deletes the matching AudioOutputController
   // instance.  Prior to deleting the AudioOutputController object, a call to
   // AudioOutputController::Close must be made.
   virtual void CloseStream(int stream_id) = 0;
 
   // Sets the volume of the audio stream.
   virtual void SetVolume(int stream_id, double volume) = 0;
 
  protected:
   virtual ~AudioOutputIPC();
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_AUDIO_OUTPUT_IPC_H_