audio_renderer.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_H_
6#define MEDIA_BASE_AUDIO_RENDERER_H_
7
8#include <list>
9
10#include "base/callback.h"
11#include "base/memory/ref_counted.h"
12#include "base/time.h"
13#include "media/base/media_export.h"
14#include "media/base/pipeline_status.h"
15
16namespace media {
17
18class AudioDecoder;
19class DemuxerStream;
20
21class MEDIA_EXPORT AudioRenderer
22    : public base::RefCountedThreadSafe<AudioRenderer> {
23 public:
24  typedef std::list<scoped_refptr<AudioDecoder> > AudioDecoderList;
25
26  // First parameter is the current time that has been rendered.
27  // Second parameter is the maximum time value that the clock cannot exceed.
28  typedef base::Callback<void(base::TimeDelta, base::TimeDelta)> TimeCB;
29
30  // Initialize a AudioRenderer with the given AudioDecoder, executing the
31  // |init_cb| upon completion.
32  //
33  // |statistics_cb| is executed periodically with audio rendering stats.
34  //
35  // |underflow_cb| is executed when the renderer runs out of data to pass to
36  // the audio card during playback. ResumeAfterUnderflow() must be called
37  // to resume playback. Pause(), Preroll(), or Stop() cancels the underflow
38  // condition.
39  //
40  // |time_cb| is executed whenever time has advanced by way of audio rendering.
41  //
42  // |ended_cb| is executed when audio rendering has reached the end of stream.
43  //
44  // |disabled_cb| is executed when audio rendering has been disabled due to
45  // external factors (i.e., device was removed). |time_cb| will no longer be
46  // executed.
47  //
48  // |error_cb| is executed if an error was encountered.
49  virtual void Initialize(const scoped_refptr<DemuxerStream>& stream,
50                          const AudioDecoderList& decoders,
51                          const PipelineStatusCB& init_cb,
52                          const StatisticsCB& statistics_cb,
53                          const base::Closure& underflow_cb,
54                          const TimeCB& time_cb,
55                          const base::Closure& ended_cb,
56                          const base::Closure& disabled_cb,
57                          const PipelineStatusCB& error_cb) = 0;
58
59  // Start audio decoding and rendering at the current playback rate, executing
60  // |callback| when playback is underway.
61  virtual void Play(const base::Closure& callback) = 0;
62
63  // Temporarily suspend decoding and rendering audio, executing |callback| when
64  // playback has been suspended.
65  virtual void Pause(const base::Closure& callback) = 0;
66
67  // Discard any audio data, executing |callback| when completed.
68  virtual void Flush(const base::Closure& callback) = 0;
69
70  // Start prerolling audio data for samples starting at |time|, executing
71  // |callback| when completed.
72  //
73  // Only valid to call after a successful Initialize() or Flush().
74  virtual void Preroll(base::TimeDelta time,
75                       const PipelineStatusCB& callback) = 0;
76
77  // Stop all operations in preparation for being deleted, executing |callback|
78  // when complete.
79  virtual void Stop(const base::Closure& callback) = 0;
80
81  // Updates the current playback rate.
82  virtual void SetPlaybackRate(float playback_rate) = 0;
83
84  // Sets the output volume.
85  virtual void SetVolume(float volume) = 0;
86
87  // Resumes playback after underflow occurs.
88  //
89  // |buffer_more_audio| is set to true if you want to increase the size of the
90  // decoded audio buffer.
91  virtual void ResumeAfterUnderflow(bool buffer_more_audio) = 0;
92
93 protected:
94  friend class base::RefCountedThreadSafe<AudioRenderer>;
95
96  AudioRenderer();
97  virtual ~AudioRenderer();
98
99 private:
100  DISALLOW_COPY_AND_ASSIGN(AudioRenderer);
101};
102
103}  // namespace media
104
105#endif  // MEDIA_BASE_AUDIO_RENDERER_H_
106