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_OUTPUT_RESAMPLER_H_ 6 #define MEDIA_AUDIO_AUDIO_OUTPUT_RESAMPLER_H_ 7 8 #include <map> 9 10 #include "base/basictypes.h" 11 #include "base/memory/ref_counted.h" 12 #include "base/time/time.h" 13 #include "media/audio/audio_io.h" 14 #include "media/audio/audio_manager.h" 15 #include "media/audio/audio_output_dispatcher.h" 16 #include "media/audio/audio_parameters.h" 17 18 namespace media { 19 20 class OnMoreDataConverter; 21 22 // AudioOutputResampler is a browser-side resampling and buffering solution 23 // which ensures audio data is always output at given parameters. See the 24 // AudioConverter class for details on the conversion process. 25 // 26 // AOR works by intercepting the AudioSourceCallback provided to StartStream() 27 // and redirecting it through an AudioConverter instance. AudioBuffersState is 28 // adjusted for buffer delay caused by the conversion process. 29 // 30 // AOR will automatically fall back from AUDIO_PCM_LOW_LATENCY to 31 // AUDIO_PCM_LINEAR if the output device fails to open at the requested output 32 // parameters. 33 // 34 // TODO(dalecurtis): Ideally the low latency path will be as reliable as the 35 // high latency path once we have channel mixing and support querying for the 36 // hardware's configured bit depth. Monitor the UMA stats for fallback and 37 // remove fallback support once it's stable. http://crbug.com/148418 38 class MEDIA_EXPORT AudioOutputResampler : public AudioOutputDispatcher { 39 public: 40 AudioOutputResampler(AudioManager* audio_manager, 41 const AudioParameters& input_params, 42 const AudioParameters& output_params, 43 const std::string& output_device_id, 44 const base::TimeDelta& close_delay); 45 46 // AudioOutputDispatcher interface. 47 virtual bool OpenStream() OVERRIDE; 48 virtual bool StartStream(AudioOutputStream::AudioSourceCallback* callback, 49 AudioOutputProxy* stream_proxy) OVERRIDE; 50 virtual void StopStream(AudioOutputProxy* stream_proxy) OVERRIDE; 51 virtual void StreamVolumeSet(AudioOutputProxy* stream_proxy, 52 double volume) OVERRIDE; 53 virtual void CloseStream(AudioOutputProxy* stream_proxy) OVERRIDE; 54 virtual void Shutdown() OVERRIDE; 55 56 private: 57 friend class base::RefCountedThreadSafe<AudioOutputResampler>; 58 virtual ~AudioOutputResampler(); 59 60 // Converts low latency based output parameters into high latency 61 // appropriate output parameters in error situations. 62 void SetupFallbackParams(); 63 64 // Used to initialize and reinitialize |dispatcher_|. 65 void Initialize(); 66 67 // Dispatcher to proxy all AudioOutputDispatcher calls too. 68 scoped_refptr<AudioOutputDispatcher> dispatcher_; 69 70 // Map of outstanding OnMoreDataConverter objects. A new object is created 71 // on every StartStream() call and destroyed on CloseStream(). 72 typedef std::map<AudioOutputProxy*, OnMoreDataConverter*> CallbackMap; 73 CallbackMap callbacks_; 74 75 // Used by AudioOutputDispatcherImpl; kept so we can reinitialize on the fly. 76 base::TimeDelta close_delay_; 77 78 // AudioParameters used to setup the output stream. 79 AudioParameters output_params_; 80 81 // Whether any streams have been opened through |dispatcher_|, if so we can't 82 // fallback on future OpenStream() failures. 83 bool streams_opened_; 84 85 DISALLOW_COPY_AND_ASSIGN(AudioOutputResampler); 86 }; 87 88 } // namespace media 89 90 #endif // MEDIA_AUDIO_AUDIO_OUTPUT_RESAMPLER_H_ 91