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_ 173
