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

content/browser/renderer_host/media/audio_sync_reader.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 CONTENT_BROWSER_RENDERER_HOST_MEDIA_AUDIO_SYNC_READER_H_
 #define CONTENT_BROWSER_RENDERER_HOST_MEDIA_AUDIO_SYNC_READER_H_
 
 #include "base/file_descriptor_posix.h"
 #include "base/process.h"
 #include "base/sync_socket.h"
 #include "base/synchronization/lock.h"
 #include "base/time.h"
 #include "media/audio/audio_output_controller.h"
 #include "media/base/audio_bus.h"
 
 namespace base {
 class SharedMemory;
 }
 
 // A AudioOutputController::SyncReader implementation using SyncSocket. This
 // is used by AudioOutputController to provide a low latency data source for
 // transmitting audio packets between the browser process and the renderer
 // process.
 class AudioSyncReader : public media::AudioOutputController::SyncReader {
  public:
   AudioSyncReader(base::SharedMemory* shared_memory,
-                  const media::AudioParameters& params);
+                  const media::AudioParameters& params,
+                  int input_channels);
 
   virtual ~AudioSyncReader();
 
   // media::AudioOutputController::SyncReader implementations.
   virtual void UpdatePendingBytes(uint32 bytes) OVERRIDE;
-  virtual int Read(media::AudioBus* audio_bus) OVERRIDE;
+  virtual int Read(media::AudioBus* source, media::AudioBus* dest) OVERRIDE;
   virtual void Close() OVERRIDE;
   virtual bool DataReady() OVERRIDE;
 
   bool Init();
   bool PrepareForeignSocketHandle(base::ProcessHandle process_handle,
 #if defined(OS_WIN)
                                   base::SyncSocket::Handle* foreign_handle);
 #else
                                   base::FileDescriptor* foreign_handle);
 #endif
 
  private:
   base::SharedMemory* shared_memory_;
   base::Time previous_call_time_;
 
+  // Number of input channels for synchronized I/O.
+  int input_channels_;
+
   // Socket for transmitting audio data.
   scoped_ptr<base::CancelableSyncSocket> socket_;
 
   // Socket to be used by the renderer. The reference is released after
   // PrepareForeignSocketHandle() is called and ran successfully.
   scoped_ptr<base::CancelableSyncSocket> foreign_socket_;
 
   // Shared memory wrapper used for transferring audio data to Read() callers.
-  scoped_ptr<media::AudioBus> audio_bus_;
+  scoped_ptr<media::AudioBus> output_bus_;
+
+  // Shared memory wrapper used for transferring audio data from Read() callers.
+  scoped_ptr<media::AudioBus> input_bus_;
 
   // Maximum amount of audio data which can be transferred in one Read() call.
   int packet_size_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioSyncReader);
 };
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_AUDIO_SYNC_READER_H_