audio_renderer_sink.h revision c2e0dbddbe15c98d52c4786dac06cb8952a8ae6d 
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  // For clients wishing to have synchronized input and output,
45  // |params| may specify |input_channels| > 0, representing a
46  // number of input channels which will be at the same sample-rate
47  // and buffer-size as the output as specified in |params|.
48  // In this case, the callback's RenderIO() method will be called instead
49  // of Render(), providing the synchronized input data at the same time as
50  // when new output data is to be rendered.
51  virtual void Initialize(const AudioParameters& params,
52                          RenderCallback* callback) = 0;
53
54  // Starts audio playback.
55  virtual void Start() = 0;
56
57  // Stops audio playback.
58  virtual void Stop() = 0;
59
60  // Pauses playback.
61  virtual void Pause() = 0;
62
63  // Resumes playback after calling Pause().
64  virtual void Play() = 0;
65
66  // Sets the playback volume, with range [0.0, 1.0] inclusive.
67  // Returns |true| on success.
68  virtual bool SetVolume(double volume) = 0;
69
70 protected:
71  friend class base::RefCountedThreadSafe<AudioRendererSink>;
72  virtual ~AudioRendererSink() {}
73};
74
75}  // namespace media
76
77#endif  // MEDIA_BASE_AUDIO_RENDERER_SINK_H_
78