audio_output_resampler.h revision a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7 
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_AUDIO_AUDIO_OUTPUT_RESAMPLER_H_
6#define MEDIA_AUDIO_AUDIO_OUTPUT_RESAMPLER_H_
7
8#include <map>
9
10#include "base/basictypes.h"
11#include "base/memory/ref_counted.h"
12#include "base/time/time.h"
13#include "media/audio/audio_io.h"
14#include "media/audio/audio_manager.h"
15#include "media/audio/audio_output_dispatcher.h"
16#include "media/audio/audio_parameters.h"
17
18namespace media {
19
20class OnMoreDataConverter;
21
22// AudioOutputResampler is a browser-side resampling and buffering solution
23// which ensures audio data is always output at given parameters.  See the
24// AudioConverter class for details on the conversion process.
25//
26// AOR works by intercepting the AudioSourceCallback provided to StartStream()
27// and redirecting it through an AudioConverter instance.  AudioBuffersState is
28// adjusted for buffer delay caused by the conversion process.
29//
30// AOR will automatically fall back from AUDIO_PCM_LOW_LATENCY to
31// AUDIO_PCM_LINEAR if the output device fails to open at the requested output
32// parameters.
33//
34// TODO(dalecurtis): Ideally the low latency path will be as reliable as the
35// high latency path once we have channel mixing and support querying for the
36// hardware's configured bit depth.  Monitor the UMA stats for fallback and
37// remove fallback support once it's stable.  http://crbug.com/148418
38class MEDIA_EXPORT AudioOutputResampler : public AudioOutputDispatcher {
39 public:
40  AudioOutputResampler(AudioManager* audio_manager,
41                       const AudioParameters& input_params,
42                       const AudioParameters& output_params,
43                       const std::string& output_device_id,
44                       const std::string& input_device_id,
45                       const base::TimeDelta& close_delay);
46
47  // AudioOutputDispatcher interface.
48  virtual bool OpenStream() OVERRIDE;
49  virtual bool StartStream(AudioOutputStream::AudioSourceCallback* callback,
50                           AudioOutputProxy* stream_proxy) OVERRIDE;
51  virtual void StopStream(AudioOutputProxy* stream_proxy) OVERRIDE;
52  virtual void StreamVolumeSet(AudioOutputProxy* stream_proxy,
53                               double volume) OVERRIDE;
54  virtual void CloseStream(AudioOutputProxy* stream_proxy) OVERRIDE;
55  virtual void Shutdown() OVERRIDE;
56  virtual void CloseStreamsForWedgeFix() OVERRIDE;
57  virtual void RestartStreamsForWedgeFix() OVERRIDE;
58
59 private:
60  friend class base::RefCountedThreadSafe<AudioOutputResampler>;
61  virtual ~AudioOutputResampler();
62
63  // Converts low latency based output parameters into high latency
64  // appropriate output parameters in error situations.
65  void SetupFallbackParams();
66
67  // Used to initialize and reinitialize |dispatcher_|.
68  void Initialize();
69
70  // Dispatcher to proxy all AudioOutputDispatcher calls too.
71  scoped_refptr<AudioOutputDispatcher> dispatcher_;
72
73  // Map of outstanding OnMoreDataConverter objects.  A new object is created
74  // on every StartStream() call and destroyed on CloseStream().
75  typedef std::map<AudioOutputProxy*, OnMoreDataConverter*> CallbackMap;
76  CallbackMap callbacks_;
77
78  // Used by AudioOutputDispatcherImpl; kept so we can reinitialize on the fly.
79  base::TimeDelta close_delay_;
80
81  // AudioParameters used to setup the output stream.
82  AudioParameters output_params_;
83
84  // Whether any streams have been opened through |dispatcher_|, if so we can't
85  // fallback on future OpenStream() failures.
86  bool streams_opened_;
87
88  DISALLOW_COPY_AND_ASSIGN(AudioOutputResampler);
89};
90
91}  // namespace media
92
93#endif  // MEDIA_AUDIO_AUDIO_OUTPUT_RESAMPLER_H_
94