audio_renderer_sink.h revision 5821806d5e7f356e8fa4b058a389a808ea183019 
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/memory/ref_counted.h"
11#include "media/audio/audio_parameters.h"
12#include "media/base/audio_bus.h"
13#include "media/base/media_export.h"
14
15namespace media {
16
17// AudioRendererSink is an interface representing the end-point for
18// rendered audio.  An implementation is expected to
19// periodically call Render() on a callback object.
20
21class AudioRendererSink
22    : public base::RefCountedThreadSafe<media::AudioRendererSink> {
23 public:
24  class RenderCallback {
25   public:
26    // Attempts to completely fill all channels of |dest|, returns actual
27    // number of frames filled.
28    virtual int Render(AudioBus* dest, int audio_delay_milliseconds) = 0;
29
30    // Synchronized audio I/O - see InitializeIO() below.
31    virtual void RenderIO(AudioBus* source,
32                          AudioBus* dest,
33                          int audio_delay_milliseconds) {}
34
35    // Signals an error has occurred.
36    virtual void OnRenderError() = 0;
37
38   protected:
39    virtual ~RenderCallback() {}
40  };
41
42  // Sets important information about the audio stream format.
43  // It must be called before any of the other methods.
44  virtual void Initialize(const AudioParameters& params,
45                          RenderCallback* callback) = 0;
46
47  // InitializeIO() may be called instead of Initialize() for clients who wish
48  // to have synchronized input and output.  |input_channels| specifies the
49  // number of input channels which will be at the same sample-rate
50  // and buffer-size as the output as specified in |params|.
51  // The callback's RenderIO() method will be called instead of Render(),
52  // providing the synchronized input data at the same time as when new
53  // output data is to be rendered.
54  virtual void InitializeIO(const AudioParameters& params,
55                            int input_channels,
56                            RenderCallback* callback) {}
57
58  // Starts audio playback.
59  virtual void Start() = 0;
60
61  // Stops audio playback.
62  virtual void Stop() = 0;
63
64  // Pauses playback.
65  virtual void Pause(bool flush) = 0;
66
67  // Resumes playback after calling Pause().
68  virtual void Play() = 0;
69
70  // Sets the playback volume, with range [0.0, 1.0] inclusive.
71  // Returns |true| on success.
72  virtual bool SetVolume(double volume) = 0;
73
74 protected:
75  friend class base::RefCountedThreadSafe<AudioRendererSink>;
76  virtual ~AudioRendererSink() {}
77};
78
79}  // namespace media
80
81#endif  // MEDIA_BASE_AUDIO_RENDERER_SINK_H_
82