media/audio/audio_io.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 #ifndef MEDIA_AUDIO_AUDIO_IO_H_
   6 #define MEDIA_AUDIO_AUDIO_IO_H_
   7
   8 #include "base/basictypes.h"
   9 #include "media/audio/audio_buffers_state.h"
  10 #include "media/base/audio_bus.h"
  11
  12 // Low-level audio output support. To make sound there are 3 objects involved:
  13 // - AudioSource : produces audio samples on a pull model. Implements
  14 //   the AudioSourceCallback interface.
  15 // - AudioOutputStream : uses the AudioSource to render audio on a given
  16 //   channel, format and sample frequency configuration. Data from the
  17 //   AudioSource is delivered in a 'pull' model.
  18 // - AudioManager : factory for the AudioOutputStream objects, manager
  19 //   of the hardware resources and mixer control.
  20 //
  21 // The number and configuration of AudioOutputStream does not need to match the
  22 // physically available hardware resources. For example you can have:
  23 //
  24 //  MonoPCMSource1 --> MonoPCMStream1 --> |       | --> audio left channel
  25 //  StereoPCMSource -> StereoPCMStream -> | mixer |
  26 //  MonoPCMSource2 --> MonoPCMStream2 --> |       | --> audio right channel
  27 //
  28 // This facility's objective is mix and render audio with low overhead using
  29 // the OS basic audio support, abstracting as much as possible the
  30 // idiosyncrasies of each platform. Non-goals:
  31 // - Positional, 3d audio
  32 // - Dependence on non-default libraries such as DirectX 9, 10, XAudio
  33 // - Digital signal processing or effects
  34 // - Extra features if a specific hardware is installed (EAX, X-fi)
  35 //
  36 // The primary client of this facility is audio coming from several tabs.
  37 // Specifically for this case we avoid supporting complex formats such as MP3
  38 // or WMA. Complex format decoding should be done by the renderers.
  39
  40
  41 // Models an audio stream that gets rendered to the audio hardware output.
  42 // Because we support more audio streams than physically available channels
  43 // a given AudioOutputStream might or might not talk directly to hardware.
  44 // An audio stream allocates several buffers for audio data and calls
  45 // AudioSourceCallback::OnMoreData() periodically to fill these buffers,
  46 // as the data is written to the audio device. Size of each packet is determined
  47 // by |samples_per_packet| specified in AudioParameters  when the stream is
  48 // created.
  49
  50 namespace media {
  51
  52 class MEDIA_EXPORT AudioOutputStream {
  53  public:
  54   // Audio sources must implement AudioSourceCallback. This interface will be
  55   // called in a random thread which very likely is a high priority thread. Do
  56   // not rely on using this thread TLS or make calls that alter the thread
  57   // itself such as creating Windows or initializing COM.
  58   class MEDIA_EXPORT AudioSourceCallback {
  59    public:
  60     // Provide more data by fully filling |dest|.  The source will return
  61     // the number of frames it filled.  |buffers_state| contains current state
  62     // of the buffers, and can be used by the source to calculate delay.
  63     virtual int OnMoreData(AudioBus* dest,
  64                            AudioBuffersState buffers_state) = 0;
  65
  66     virtual int OnMoreIOData(AudioBus* source,
  67                              AudioBus* dest,
  68                              AudioBuffersState buffers_state) = 0;
  69
  70     // There was an error while playing a buffer. Audio source cannot be
  71     // destroyed yet. No direct action needed by the AudioStream, but it is
  72     // a good place to stop accumulating sound data since is is likely that
  73     // playback will not continue.
  74     virtual void OnError(AudioOutputStream* stream) = 0;
  75
  76    protected:
  77     virtual ~AudioSourceCallback() {}
  78   };
  79
  80   virtual ~AudioOutputStream() {}
  81
  82   // Open the stream. false is returned if the stream cannot be opened.  Open()
  83   // must always be followed by a call to Close() even if Open() fails.
  84   virtual bool Open() = 0;
  85
  86   // Starts playing audio and generating AudioSourceCallback::OnMoreData().
  87   // Since implementor of AudioOutputStream may have internal buffers, right
  88   // after calling this method initial buffers are fetched.
  89   //
  90   // The output stream does not take ownership of this callback.
  91   virtual void Start(AudioSourceCallback* callback) = 0;
  92
  93   // Stops playing audio. Effect might not be instantaneous as the hardware
  94   // might have locked audio data that is processing.
  95   virtual void Stop() = 0;
  96
  97   // Sets the relative volume, with range [0.0, 1.0] inclusive.
  98   virtual void SetVolume(double volume) = 0;
  99
 100   // Gets the relative volume, with range [0.0, 1.0] inclusive.
 101   virtual void GetVolume(double* volume) = 0;
 102
 103   // Close the stream. This also generates AudioSourceCallback::OnClose().
 104   // After calling this method, the object should not be used anymore.
 105   virtual void Close() = 0;
 106 };
 107
 108 // Models an audio sink receiving recorded audio from the audio driver.
 109 class MEDIA_EXPORT AudioInputStream {
 110  public:
 111   class MEDIA_EXPORT AudioInputCallback {
 112    public:
 113     // Called by the audio recorder when a full packet of audio data is
 114     // available. This is called from a special audio thread and the
 115     // implementation should return as soon as possible.
 116     virtual void OnData(AudioInputStream* stream, const uint8* src,
 117                         uint32 size, uint32 hardware_delay_bytes,
 118                         double volume) = 0;
 119
 120     // The stream is done with this callback, the last call received by this
 121     // audio sink.
 122     virtual void OnClose(AudioInputStream* stream) = 0;
 123
 124     // There was an error while recording audio. The audio sink cannot be
 125     // destroyed yet. No direct action needed by the AudioInputStream, but it
 126     // is a good place to stop accumulating sound data since is is likely that
 127     // recording will not continue.
 128     virtual void OnError(AudioInputStream* stream) = 0;
 129
 130    protected:
 131     virtual ~AudioInputCallback() {}
 132   };
 133
 134   virtual ~AudioInputStream() {}
 135
 136   // Open the stream and prepares it for recording. Call Start() to actually
 137   // begin recording.
 138   virtual bool Open() = 0;
 139
 140   // Starts recording audio and generating AudioInputCallback::OnData().
 141   // The input stream does not take ownership of this callback.
 142   virtual void Start(AudioInputCallback* callback) = 0;
 143
 144   // Stops recording audio. Effect might not be instantaneous as there could be
 145   // pending audio callbacks in the queue which will be issued first before
 146   // recording stops.
 147   virtual void Stop() = 0;
 148
 149   // Close the stream. This also generates AudioInputCallback::OnClose(). This
 150   // should be the last call made on this object.
 151   virtual void Close() = 0;
 152
 153   // Returns the maximum microphone analog volume or 0.0 if device does not
 154   // have volume control.
 155   virtual double GetMaxVolume() = 0;
 156
 157   // Sets the microphone analog volume, with range [0, max_volume] inclusive.
 158   virtual void SetVolume(double volume) = 0;
 159
 160   // Returns the microphone analog volume, with range [0, max_volume] inclusive.
 161   virtual double GetVolume() = 0;
 162
 163   // Sets the Automatic Gain Control (AGC) state.
 164   virtual void SetAutomaticGainControl(bool enabled) = 0;
 165
 166   // Returns the Automatic Gain Control (AGC) state.
 167   virtual bool GetAutomaticGainControl() = 0;
 168 };
 169
 170 }  // namespace media
 171
 172 #endif  // MEDIA_AUDIO_AUDIO_IO_H_