media/base/audio_renderer_sink.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_BASE_AUDIO_RENDERER_SINK_H_
   6 #define MEDIA_BASE_AUDIO_RENDERER_SINK_H_
   7
   8 #include <vector>
   9 #include "base/basictypes.h"
  10 #include "base/logging.h"
  11 #include "base/memory/ref_counted.h"
  12 #include "media/audio/audio_parameters.h"
  13 #include "media/base/audio_bus.h"
  14 #include "media/base/media_export.h"
  15
  16 namespace media {
  17
  18 // AudioRendererSink is an interface representing the end-point for
  19 // rendered audio.  An implementation is expected to
  20 // periodically call Render() on a callback object.
  21
  22 class AudioRendererSink
  23     : public base::RefCountedThreadSafe<media::AudioRendererSink> {
  24  public:
  25   class RenderCallback {
  26    public:
  27     // Attempts to completely fill all channels of |dest|, returns actual
  28     // number of frames filled.
  29     virtual int Render(AudioBus* dest, int audio_delay_milliseconds) = 0;
  30
  31     // Signals an error has occurred.
  32     virtual void OnRenderError() = 0;
  33
  34    protected:
  35     virtual ~RenderCallback() {}
  36   };
  37
  38   // Sets important information about the audio stream format.
  39   // It must be called before any of the other methods.
  40   virtual void Initialize(const AudioParameters& params,
  41                           RenderCallback* callback) = 0;
  42
  43   // Starts audio playback.
  44   virtual void Start() = 0;
  45
  46   // Stops audio playback.
  47   virtual void Stop() = 0;
  48
  49   // Pauses playback.
  50   virtual void Pause() = 0;
  51
  52   // Resumes playback after calling Pause().
  53   virtual void Play() = 0;
  54
  55   // Sets the playback volume, with range [0.0, 1.0] inclusive.
  56   // Returns |true| on success.
  57   virtual bool SetVolume(double volume) = 0;
  58
  59  protected:
  60   friend class base::RefCountedThreadSafe<AudioRendererSink>;
  61   virtual ~AudioRendererSink() {}
  62 };
  63
  64 }  // namespace media
  65
  66 #endif  // MEDIA_BASE_AUDIO_RENDERER_SINK_H_