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     // Synchronized audio I/O - see InitializeIO() below.
  32     virtual void RenderIO(AudioBus* source,
  33                           AudioBus* dest,
  34                           int audio_delay_milliseconds) {}
  35
  36     // Signals an error has occurred.
  37     virtual void OnRenderError() = 0;
  38
  39    protected:
  40     virtual ~RenderCallback() {}
  41   };
  42
  43   // Sets important information about the audio stream format.
  44   // It must be called before any of the other methods.
  45   virtual void Initialize(const AudioParameters& params,
  46                           RenderCallback* callback) = 0;
  47
  48   // Starts audio playback.
  49   virtual void Start() = 0;
  50
  51   // Stops audio playback.
  52   virtual void Stop() = 0;
  53
  54   // Pauses playback.
  55   virtual void Pause() = 0;
  56
  57   // Resumes playback after calling Pause().
  58   virtual void Play() = 0;
  59
  60   // Sets the playback volume, with range [0.0, 1.0] inclusive.
  61   // Returns |true| on success.
  62   virtual bool SetVolume(double volume) = 0;
  63
  64  protected:
  65   friend class base::RefCountedThreadSafe<AudioRendererSink>;
  66   virtual ~AudioRendererSink() {}
  67 };
  68
  69 }  // namespace media
  70
  71 #endif  // MEDIA_BASE_AUDIO_RENDERER_SINK_H_