media/audio/audio_output_resampler.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_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 "base/timer/timer.h"
  14 #include "media/audio/audio_io.h"
  15 #include "media/audio/audio_manager.h"
  16 #include "media/audio/audio_output_dispatcher_impl.h"
  17 #include "media/audio/audio_parameters.h"
  18
  19 namespace media {
  20
  21 class OnMoreDataConverter;
  22
  23 // AudioOutputResampler is a browser-side resampling and buffering solution
  24 // which ensures audio data is always output at given parameters.  See the
  25 // AudioConverter class for details on the conversion process.
  26 //
  27 // AOR works by intercepting the AudioSourceCallback provided to StartStream()
  28 // and redirecting it through an AudioConverter instance.  |total_bytes_delay|
  29 // is adjusted for buffer delay caused by the conversion process.
  30 //
  31 // AOR will automatically fall back from AUDIO_PCM_LOW_LATENCY to
  32 // AUDIO_PCM_LINEAR if the output device fails to open at the requested output
  33 // parameters. If opening still fails, it will fallback to AUDIO_FAKE.
  34 class MEDIA_EXPORT AudioOutputResampler : public AudioOutputDispatcher {
  35  public:
  36   AudioOutputResampler(AudioManager* audio_manager,
  37                        const AudioParameters& input_params,
  38                        const AudioParameters& output_params,
  39                        const std::string& output_device_id,
  40                        const base::TimeDelta& close_delay);
  41
  42   // AudioOutputDispatcher interface.
  43   bool OpenStream() override;
  44   bool StartStream(AudioOutputStream::AudioSourceCallback* callback,
  45                    AudioOutputProxy* stream_proxy) override;
  46   void StopStream(AudioOutputProxy* stream_proxy) override;
  47   void StreamVolumeSet(AudioOutputProxy* stream_proxy, double volume) override;
  48   void CloseStream(AudioOutputProxy* stream_proxy) override;
  49   void Shutdown() override;
  50
  51  private:
  52   friend class base::RefCountedThreadSafe<AudioOutputResampler>;
  53   ~AudioOutputResampler() override;
  54
  55   // Converts low latency based output parameters into high latency
  56   // appropriate output parameters in error situations.
  57   void SetupFallbackParams();
  58
  59   // Used to reinitialize |dispatcher_|.
  60   void Reinitialize();
  61
  62   // Used to initialize |dispatcher_|.
  63   void Initialize();
  64
  65   // Dispatcher to proxy all AudioOutputDispatcher calls too.
  66   scoped_refptr<AudioOutputDispatcherImpl> dispatcher_;
  67
  68   // Map of outstanding OnMoreDataConverter objects.  A new object is created
  69   // on every StartStream() call and destroyed on CloseStream().
  70   typedef std::map<AudioOutputProxy*, OnMoreDataConverter*> CallbackMap;
  71   CallbackMap callbacks_;
  72
  73   // Used by AudioOutputDispatcherImpl; kept so we can reinitialize on the fly.
  74   base::TimeDelta close_delay_;
  75
  76   // AudioParameters used to setup the output stream; changed upon fallback.
  77   AudioParameters output_params_;
  78
  79   // The original AudioParameters we were constructed with.
  80   const AudioParameters original_output_params_;
  81
  82   // Whether any streams have been opened through |dispatcher_|, if so we can't
  83   // fallback on future OpenStream() failures.
  84   bool streams_opened_;
  85
  86   // The reinitialization timer provides a way to recover from temporary failure
  87   // states by clearing the dispatcher if all proxies have been closed and none
  88   // have been created within |close_delay_|.  Without this, audio may be lost
  89   // to a fake stream indefinitely for transient errors.
  90   base::Timer reinitialize_timer_;
  91
  92   DISALLOW_COPY_AND_ASSIGN(AudioOutputResampler);
  93 };
  94
  95 }  // namespace media
  96
  97 #endif  // MEDIA_AUDIO_AUDIO_OUTPUT_RESAMPLER_H_