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     virtual ~AudioSourceCallback() {}
  60
  61     // Provide more data by fully filling |dest|.  The source will return
  62     // the number of frames it filled.  |total_bytes_delay| contains current
  63     // number of bytes of delay buffered by the AudioOutputStream.
  64     virtual int OnMoreData(AudioBus* dest, uint32 total_bytes_delay) = 0;
  65
  66     // There was an error while playing a buffer. Audio source cannot be
  67     // destroyed yet. No direct action needed by the AudioStream, but it is
  68     // a good place to stop accumulating sound data since is is likely that
  69     // playback will not continue.
  70     virtual void OnError(AudioOutputStream* stream) = 0;
  71   };
  72
  73   virtual ~AudioOutputStream() {}
  74
  75   // Open the stream. false is returned if the stream cannot be opened.  Open()
  76   // must always be followed by a call to Close() even if Open() fails.
  77   virtual bool Open() = 0;
  78
  79   // Starts playing audio and generating AudioSourceCallback::OnMoreData().
  80   // Since implementor of AudioOutputStream may have internal buffers, right
  81   // after calling this method initial buffers are fetched.
  82   //
  83   // The output stream does not take ownership of this callback.
  84   virtual void Start(AudioSourceCallback* callback) = 0;
  85
  86   // Stops playing audio. Effect might not be instantaneous as the hardware
  87   // might have locked audio data that is processing.
  88   virtual void Stop() = 0;
  89
  90   // Sets the relative volume, with range [0.0, 1.0] inclusive.
  91   virtual void SetVolume(double volume) = 0;
  92
  93   // Gets the relative volume, with range [0.0, 1.0] inclusive.
  94   virtual void GetVolume(double* volume) = 0;
  95
  96   // Close the stream. This also generates AudioSourceCallback::OnClose().
  97   // After calling this method, the object should not be used anymore.
  98   virtual void Close() = 0;
  99 };
 100
 101 // Models an audio sink receiving recorded audio from the audio driver.
 102 class MEDIA_EXPORT AudioInputStream {
 103  public:
 104   class MEDIA_EXPORT AudioInputCallback {
 105    public:
 106     // Called by the audio recorder when a full packet of audio data is
 107     // available. This is called from a special audio thread and the
 108     // implementation should return as soon as possible.
 109     // TODO(henrika): should be pure virtual when old OnData() is phased out.
 110     virtual void OnData(AudioInputStream* stream,
 111                         const AudioBus* source,
 112                         uint32 hardware_delay_bytes,
 113                         double volume) {};
 114
 115     // TODO(henrika): don't use; to be removed.
 116     virtual void OnData(AudioInputStream* stream,
 117                         const uint8* src,
 118                         uint32 size,
 119                         uint32 hardware_delay_bytes,
 120                         double volume) {};
 121
 122     // There was an error while recording audio. The audio sink cannot be
 123     // destroyed yet. No direct action needed by the AudioInputStream, but it
 124     // is a good place to stop accumulating sound data since is is likely that
 125     // recording will not continue.
 126     virtual void OnError(AudioInputStream* stream) = 0;
 127
 128    protected:
 129     virtual ~AudioInputCallback() {}
 130   };
 131
 132   virtual ~AudioInputStream() {}
 133
 134   // Open the stream and prepares it for recording. Call Start() to actually
 135   // begin recording.
 136   virtual bool Open() = 0;
 137
 138   // Starts recording audio and generating AudioInputCallback::OnData().
 139   // The input stream does not take ownership of this callback.
 140   virtual void Start(AudioInputCallback* callback) = 0;
 141
 142   // Stops recording audio. Effect might not be instantaneous as there could be
 143   // pending audio callbacks in the queue which will be issued first before
 144   // recording stops.
 145   virtual void Stop() = 0;
 146
 147   // Close the stream. This also generates AudioInputCallback::OnClose(). This
 148   // should be the last call made on this object.
 149   virtual void Close() = 0;
 150
 151   // Returns the maximum microphone analog volume or 0.0 if device does not
 152   // have volume control.
 153   virtual double GetMaxVolume() = 0;
 154
 155   // Sets the microphone analog volume, with range [0, max_volume] inclusive.
 156   virtual void SetVolume(double volume) = 0;
 157
 158   // Returns the microphone analog volume, with range [0, max_volume] inclusive.
 159   virtual double GetVolume() = 0;
 160
 161   // Sets the Automatic Gain Control (AGC) state.
 162   virtual bool SetAutomaticGainControl(bool enabled) = 0;
 163
 164   // Returns the Automatic Gain Control (AGC) state.
 165   virtual bool GetAutomaticGainControl() = 0;
 166
 167   // Returns the current muting state for the microphone.
 168   virtual bool IsMuted() = 0;
 169 };
 170
 171 }  // namespace media
 172
 173 #endif  // MEDIA_AUDIO_AUDIO_IO_H_