Add Mac OS X unified audio I/O back-end

media/audio/mac/audio_unified_mac.h

Index: media/audio/mac/audio_unified_mac.h
===================================================================
--- media/audio/mac/audio_unified_mac.h	(revision 0)
+++ media/audio/mac/audio_unified_mac.h	(revision 0)
@@ -0,0 +1,100 @@
+// 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_MAC_AUDIO_UNIFIED_MAC_H_
+#define MEDIA_AUDIO_MAC_AUDIO_UNIFIED_MAC_H_
+
+#include <AudioUnit/AudioUnit.h>
+
+#include "base/memory/scoped_ptr.h"
+#include "media/audio/audio_io.h"
+#include "media/audio/audio_parameters.h"
+
+namespace media {
+
+class AudioManagerMac;
+
+// Implementation of AudioOutputStream for Mac OS X using the
+// CoreAudio AudioHardware API suitable for low-latency unified audio I/O
+// when using devices which support *both* input and output
+// in the same driver.  This is the case with professional
+// USB and Firewire devices.
+//
+// Please note that it's required to first get the native sample-rate of the
+// default output device and use that sample-rate when creating this object.
+class AudioHardwareUnifiedStream : public AudioOutputStream {
+ public:
+  // The ctor takes all the usual parameters, plus |manager| which is the
+  // the audio manager who is creating this object.
+  AudioHardwareUnifiedStream(AudioManagerMac* manager,
+                             const AudioParameters& params);
+  // The dtor is typically called by the AudioManager only and it is usually
+  // triggered by calling AudioOutputStream::Close().
+  virtual ~AudioHardwareUnifiedStream();
+
+  // Implementation of AudioOutputStream.
+  virtual bool Open() OVERRIDE;
+  virtual void Close() OVERRIDE;
+  virtual void Start(AudioSourceCallback* callback) OVERRIDE;
+  virtual void Stop() OVERRIDE;
+  virtual void SetVolume(double volume) OVERRIDE;
+  virtual void GetVolume(double* volume) OVERRIDE;
+
+  int input_channels() const { return input_channels_; }
+  int output_channels() const { return output_channels_; }
+
+ private:
+  OSStatus Render(AudioDeviceID device,
+                  const AudioTimeStamp* now,
+                  const AudioBufferList* input_data,
+                  const AudioTimeStamp* input_time,
+                  AudioBufferList* output_data,
+                  const AudioTimeStamp* output_time);
+
+  static OSStatus RenderProc(AudioDeviceID device,
+                             const AudioTimeStamp* now,
+                             const AudioBufferList* input_data,
+                             const AudioTimeStamp* input_time,
+                             AudioBufferList* output_data,
+                             const AudioTimeStamp* output_time,
+                             void* user_data);
+
+  // Our creator, the audio manager needs to be notified when we close.
+  AudioManagerMac* manager_;
+
+  // Pointer to the object that will provide the audio samples.
+  AudioSourceCallback* source_;
+
+  // Structure that holds the stream format details such as bitrate.
+  AudioStreamBasicDescription format_;
+
+  // Hardware buffer size.
+  int number_of_frames_;
+
+  // Number of audio channels provided to the client via OnMoreIOData().
+  int client_input_channels_;
+
+  // Volume level from 0 to 1.
+  float volume_;
+
+  // Number of input and output channels queried from the hardware.
+  int input_channels_;
+  int output_channels_;
+  int input_channels_per_frame_;
+  int output_channels_per_frame_;
+
+  AudioDeviceIOProcID io_proc_id_;
+  AudioDeviceID device_;
+  bool is_playing_;
+
+  // Intermediate buffers used with call to OnMoreIOData().
+  scoped_ptr<AudioBus> input_bus_;
+  scoped_ptr<AudioBus> output_bus_;
+
+  DISALLOW_COPY_AND_ASSIGN(AudioHardwareUnifiedStream);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_AUDIO_MAC_AUDIO_UNIFIED_MAC_H_