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/base/audio_bus.h"
  10
  11 // Low-level audio output support. To make sound there are 3 objects involved:
  12 // - AudioSource : produces audio samples on a pull model. Implements
  13 //   the AudioSourceCallback interface.
  14 // - AudioOutputStream : uses the AudioSource to render audio on a given
  15 //   channel, format and sample frequency configuration. Data from the
  16 //   AudioSource is delivered in a 'pull' model.
  17 // - AudioManager : factory for the AudioOutputStream objects, manager
  18 //   of the hardware resources and mixer control.
  19 //
  20 // The number and configuration of AudioOutputStream does not need to match the
  21 // physically available hardware resources. For example you can have:
  22 //
  23 //  MonoPCMSource1 --> MonoPCMStream1 --> |       | --> audio left channel
  24 //  StereoPCMSource -> StereoPCMStream -> | mixer |
  25 //  MonoPCMSource2 --> MonoPCMStream2 --> |       | --> audio right channel
  26 //
  27 // This facility's objective is mix and render audio with low overhead using
  28 // the OS basic audio support, abstracting as much as possible the
  29 // idiosyncrasies of each platform. Non-goals:
  30 // - Positional, 3d audio
  31 // - Dependence on non-default libraries such as DirectX 9, 10, XAudio
  32 // - Digital signal processing or effects
  33 // - Extra features if a specific hardware is installed (EAX, X-fi)
  34 //
  35 // The primary client of this facility is audio coming from several tabs.
  36 // Specifically for this case we avoid supporting complex formats such as MP3
  37 // or WMA. Complex format decoding should be done by the renderers.
  38
  39
  40 // Models an audio stream that gets rendered to the audio hardware output.
  41 // Because we support more audio streams than physically available channels
  42 // a given AudioOutputStream might or might not talk directly to hardware.
  43 // An audio stream allocates several buffers for audio data and calls
  44 // AudioSourceCallback::OnMoreData() periodically to fill these buffers,
  45 // as the data is written to the audio device. Size of each packet is determined
  46 // by |samples_per_packet| specified in AudioParameters  when the stream is
  47 // created.
  48
  49 namespace media {
  50
  51 class MEDIA_EXPORT AudioOutputStream {
  52  public:
  53   // Audio sources must implement AudioSourceCallback. This interface will be
  54   // called in a random thread which very likely is a high priority thread. Do
  55   // not rely on using this thread TLS or make calls that alter the thread
  56   // itself such as creating Windows or initializing COM.
  57   class MEDIA_EXPORT AudioSourceCallback {
  58    public:
  59     // Provide more data by fully filling |dest|.  The source will return
  60     // the number of frames it filled.  |total_bytes_delay| contains current
  61     // number of bytes of delay buffered by the AudioOutputStream.
  62     virtual int OnMoreData(AudioBus* dest, uint32 total_bytes_delay) = 0;
  63
  64     // There was an error while playing a buffer. Audio source cannot be
  65     // destroyed yet. No direct action needed by the AudioStream, but it is
  66     // a good place to stop accumulating sound data since is is likely that
  67     // playback will not continue.
  68     virtual void OnError(AudioOutputStream* stream) = 0;
  69
  70    protected:
  71     virtual ~AudioSourceCallback() {}
  72   };
  73
  74   virtual ~AudioOutputStream() {}
  75
  76   // Open the stream. false is returned if the stream cannot be opened.  Open()
  77   // must always be followed by a call to Close() even if Open() fails.
  78   virtual bool Open() = 0;
  79
  80   // Starts playing audio and generating AudioSourceCallback::OnMoreData().
  81   // Since implementor of AudioOutputStream may have internal buffers, right
  82   // after calling this method initial buffers are fetched.
  83   //
  84   // The output stream does not take ownership of this callback.
  85   virtual void Start(AudioSourceCallback* callback) = 0;
  86
  87   // Stops playing audio. Effect might not be instantaneous as the hardware
  88   // might have locked audio data that is processing.
  89   virtual void Stop() = 0;
  90
  91   // Sets the relative volume, with range [0.0, 1.0] inclusive.
  92   virtual void SetVolume(double volume) = 0;
  93
  94   // Gets the relative volume, with range [0.0, 1.0] inclusive.
  95   virtual void GetVolume(double* volume) = 0;
  96
  97   // Close the stream. This also generates AudioSourceCallback::OnClose().
  98   // After calling this method, the object should not be used anymore.
  99   virtual void Close() = 0;
 100 };
 101
 102 // Models an audio sink receiving recorded audio from the audio driver.
 103 class MEDIA_EXPORT AudioInputStream {
 104  public:
 105   class MEDIA_EXPORT AudioInputCallback {
 106    public:
 107     // Called by the audio recorder when a full packet of audio data is
 108     // available. This is called from a special audio thread and the
 109     // implementation should return as soon as possible.
 110     // TODO(henrika): should be pure virtual when old OnData() is phased out.
 111     virtual void OnData(AudioInputStream* stream,
 112                         const AudioBus* source,
 113                         uint32 hardware_delay_bytes,
 114                         double volume) {};
 115
 116     // TODO(henrika): don't use; to be removed.
 117     virtual void OnData(AudioInputStream* stream,
 118                         const uint8* src,
 119                         uint32 size,
 120                         uint32 hardware_delay_bytes,
 121                         double volume) {};
 122
 123     // There was an error while recording audio. The audio sink cannot be
 124     // destroyed yet. No direct action needed by the AudioInputStream, but it
 125     // is a good place to stop accumulating sound data since is is likely that
 126     // recording will not continue.
 127     virtual void OnError(AudioInputStream* stream) = 0;
 128
 129    protected:
 130     virtual ~AudioInputCallback() {}
 131   };
 132
 133   virtual ~AudioInputStream() {}
 134
 135   // Open the stream and prepares it for recording. Call Start() to actually
 136   // begin recording.
 137   virtual bool Open() = 0;
 138
 139   // Starts recording audio and generating AudioInputCallback::OnData().
 140   // The input stream does not take ownership of this callback.
 141   virtual void Start(AudioInputCallback* callback) = 0;
 142
 143   // Stops recording audio. Effect might not be instantaneous as there could be
 144   // pending audio callbacks in the queue which will be issued first before
 145   // recording stops.
 146   virtual void Stop() = 0;
 147
 148   // Close the stream. This also generates AudioInputCallback::OnClose(). This
 149   // should be the last call made on this object.
 150   virtual void Close() = 0;
 151
 152   // Returns the maximum microphone analog volume or 0.0 if device does not
 153   // have volume control.
 154   virtual double GetMaxVolume() = 0;
 155
 156   // Sets the microphone analog volume, with range [0, max_volume] inclusive.
 157   virtual void SetVolume(double volume) = 0;
 158
 159   // Returns the microphone analog volume, with range [0, max_volume] inclusive.
 160   virtual double GetVolume() = 0;
 161
 162   // Sets the Automatic Gain Control (AGC) state.
 163   virtual void SetAutomaticGainControl(bool enabled) = 0;
 164
 165   // Returns the Automatic Gain Control (AGC) state.
 166   virtual bool GetAutomaticGainControl() = 0;
 167
 168   // Returns the current muting state for the microphone.
 169   virtual bool IsMuted() = 0;
 170 };
 171
 172 }  // namespace media
 173
 174 #endif  // MEDIA_AUDIO_AUDIO_IO_H_