Adding microphone volume support to chrome.

media/audio/mac/audio_low_latency_input_mac.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.
 //
 // Implementation of AudioInputStream for Mac OS X using the special AUHAL
 // input Audio Unit present in OS 10.4 and later.
 // The AUHAL input Audio Unit is for low-latency audio I/O.
 //
 // Overview of operation:
 //
@@ skipping 11 matching lines @@
 //   and notify the audio manager, which likely will destroy this object.
 //
 // Implementation notes:
 //
 // - It is recommended to first acquire the native sample rate of the default
 //   input device and then use the same rate when creating this object.
 //   Use AUAudioInputStream::HardwareSampleRate() to retrieve the sample rate.
 // - Calling Close() also leads to self destruction.
 // - The latency consists of two parts:
 //   1) Hardware latency, which includes Audio Unit latency, audio device
-//      latency;
+//      latency and audio stream latency;
 //   2) The delay between the actual recording instant and the time when the
 //      data packet is provided as a callback.
 //
 #ifndef MEDIA_AUDIO_MAC_AUDIO_LOW_LATENCY_INPUT_MAC_H_
 #define MEDIA_AUDIO_MAC_AUDIO_LOW_LATENCY_INPUT_MAC_H_
 
 #include <AudioUnit/AudioUnit.h>
 
 #include "base/memory/scoped_ptr.h"
 #include "base/synchronization/lock.h"
@@ skipping 11 matching lines @@
                      AudioDeviceID audio_device_id);
   // The dtor is typically called by the AudioManager only and it is usually
   // triggered by calling AudioInputStream::Close().
   virtual ~AUAudioInputStream();
 
   // Implementation of AudioInputStream.
   virtual bool Open() OVERRIDE;
   virtual void Start(AudioInputCallback* callback) OVERRIDE;
   virtual void Stop() OVERRIDE;
   virtual void Close() OVERRIDE;
+  virtual double GetMaxVolume() OVERRIDE;
+  virtual void SetVolume(double volume) OVERRIDE;
+  virtual double GetVolume() OVERRIDE;
 
   // Returns the current hardware sample rate for the default input device.
   static double HardwareSampleRate();
 
   bool started() const { return started_; }
   AudioUnit audio_unit() { return audio_unit_; }
   AudioBufferList* audio_buffer_list() { return &audio_buffer_list_; }
 
  private:
   // AudioOutputUnit callback.
   static OSStatus InputProc(void* user_data,
                             AudioUnitRenderActionFlags* flags,
                             const AudioTimeStamp* time_stamp,
                             UInt32 bus_number,
                             UInt32 number_of_frames,
                             AudioBufferList* io_data);
 
   // Pushes recorded data to consumer of the input audio stream.
   OSStatus Provide(UInt32 number_of_frames, AudioBufferList* io_data,
                    const AudioTimeStamp* time_stamp);
 
   // Gets the fixed capture hardware latency and store it during initialization.
   // Returns 0 if not available.
   double GetHardwareLatency();
 
   // Gets the current capture delay value.
   double GetCaptureLatency(const AudioTimeStamp* input_time_stamp);
 
+  // Gets the number of channels for a stream of audio data.
+  UInt32 GetNumberOfChannelsFromStream();
+
   // Issues the OnError() callback to the |sink_|.
   void HandleError(OSStatus err);
 
+  // Helper function to check if the volume control is avialable on specific
+  // channel.
+  bool IsVolumeSettableOnChannel(int channel);
+
   // Our creator, the audio manager needs to be notified when we close.
   AudioManagerMac* manager_;
 
   // Contains the desired number of audio frames in each callback.
   size_t number_of_frames_;
 
   // Pointer to the object that will receive the recorded audio samples.
   AudioInputCallback* sink_;
 
   // Structure that holds the desired output format of the stream.
@@ skipping 14 matching lines @@
   // Temporary storage for recorded data. The InputProc() renders into this
   // array as soon as a frame of the desired buffer size has been recorded.
   scoped_array<uint8> audio_data_buffer_;
 
   // True after successfull Start(), false after successful Stop().
   bool started_;
 
   // Fixed capture hardware latency in frames.
   double hardware_latency_frames_;
 
+  // The number of channels in each frame of audio data, which is used
+  // when querying the volume of each channel.
+  UInt32 number_of_channels_in_frame_;
+
   DISALLOW_COPY_AND_ASSIGN(AUAudioInputStream);
 };
 
 #endif  // MEDIA_AUDIO_MAC_AUDIO_LOW_LATENCY_INPUT_MAC_H_