media/audio/mac/audio_low_latency_output_mac.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4 //
   5 // Implementation notes:
   6 //
   7 // - It is recommended to first acquire the native sample rate of the default
   8 //   output device and then use the same rate when creating this object.
   9 //   Use AUAudioOutputStream::HardwareSampleRate() to retrieve the sample rate.
  10 // - Calling Close() also leads to self destruction.
  11 // - The latency consists of two parts:
  12 //   1) Hardware latency, which includes Audio Unit latency, audio device
  13 //      latency;
  14 //   2) The delay between the moment getting the callback and the scheduled time
  15 //      stamp that tells when the data is going to be played out.
  16 //
  17 #ifndef MEDIA_AUDIO_MAC_AUDIO_LOW_LATENCY_OUTPUT_MAC_H_
  18 #define MEDIA_AUDIO_MAC_AUDIO_LOW_LATENCY_OUTPUT_MAC_H_
  19
  20 #include <AudioUnit/AudioUnit.h>
  21 #include <CoreAudio/CoreAudio.h>
  22
  23 #include "base/compiler_specific.h"
  24 #include "base/synchronization/lock.h"
  25 #include "media/audio/audio_io.h"
  26 #include "media/audio/audio_parameters.h"
  27
  28 namespace media {
  29
  30 class AudioManagerMac;
  31
  32 // Implementation of AudioOuputStream for Mac OS X using the
  33 // default output Audio Unit present in OS 10.4 and later.
  34 // The default output Audio Unit is for low-latency audio I/O.
  35 class AUAudioOutputStream : public AudioOutputStream {
  36  public:
  37   // The ctor takes all the usual parameters, plus |manager| which is the
  38   // the audio manager who is creating this object.
  39   AUAudioOutputStream(AudioManagerMac* manager,
  40                       const AudioParameters& params);
  41   // The dtor is typically called by the AudioManager only and it is usually
  42   // triggered by calling AudioOutputStream::Close().
  43   virtual ~AUAudioOutputStream();
  44
  45   // Implementation of AudioOutputStream.
  46   virtual bool Open() OVERRIDE;
  47   virtual void Close() OVERRIDE;
  48   virtual void Start(AudioSourceCallback* callback) OVERRIDE;
  49   virtual void Stop() OVERRIDE;
  50   virtual void SetVolume(double volume) OVERRIDE;
  51   virtual void GetVolume(double* volume) OVERRIDE;
  52
  53   static int HardwareSampleRate();
  54
  55  private:
  56   // DefaultOutputUnit callback.
  57   static OSStatus InputProc(void* user_data,
  58                             AudioUnitRenderActionFlags* flags,
  59                             const AudioTimeStamp* time_stamp,
  60                             UInt32 bus_number,
  61                             UInt32 number_of_frames,
  62                             AudioBufferList* io_data);
  63
  64   OSStatus Render(UInt32 number_of_frames, AudioBufferList* io_data,
  65                   const AudioTimeStamp* output_time_stamp);
  66
  67   // Sets up the stream format for the default output Audio Unit.
  68   bool Configure();
  69
  70   // Gets the fixed playout device hardware latency and stores it. Returns 0
  71   // if not available.
  72   double GetHardwareLatency();
  73
  74   // Gets the current playout latency value.
  75   double GetPlayoutLatency(const AudioTimeStamp* output_time_stamp);
  76
  77   // Our creator, the audio manager needs to be notified when we close.
  78   AudioManagerMac* manager_;
  79
  80   size_t number_of_frames_;
  81
  82   // Pointer to the object that will provide the audio samples.
  83   AudioSourceCallback* source_;
  84
  85   // Protects |source_|.  Necessary since Render() calls seem to be in flight
  86   // when |output_unit_| is supposedly stopped.  See http://crbug.com/178765.
  87   base::Lock source_lock_;
  88
  89   // Structure that holds the stream format details such as bitrate.
  90   AudioStreamBasicDescription format_;
  91
  92   // The default output Audio Unit which talks to the audio hardware.
  93   AudioUnit output_unit_;
  94
  95   // The UID refers to the current output audio device.
  96   AudioDeviceID output_device_id_;
  97
  98   // Volume level from 0 to 1.
  99   float volume_;
 100
 101   // Fixed playout hardware latency in frames.
 102   double hardware_latency_frames_;
 103
 104   // The flag used to stop the streaming.
 105   bool stopped_;
 106
 107   // Container for retrieving data from AudioSourceCallback::OnMoreData().
 108   scoped_ptr<AudioBus> audio_bus_;
 109
 110   DISALLOW_COPY_AND_ASSIGN(AUAudioOutputStream);
 111 };
 112
 113 }  // namespace media
 114
 115 #endif  // MEDIA_AUDIO_MAC_AUDIO_LOW_LATENCY_OUTPUT_MAC_H_