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 base::TimeDelta& close_delay);
45
46  // AudioOutputDispatcher interface.
47  virtual bool OpenStream() OVERRIDE;
48  virtual bool StartStream(AudioOutputStream::AudioSourceCallback* callback,
49                           AudioOutputProxy* stream_proxy) OVERRIDE;
50  virtual void StopStream(AudioOutputProxy* stream_proxy) OVERRIDE;
51  virtual void StreamVolumeSet(AudioOutputProxy* stream_proxy,
52                               double volume) OVERRIDE;
53  virtual void CloseStream(AudioOutputProxy* stream_proxy) OVERRIDE;
54  virtual void Shutdown() OVERRIDE;
55
56 private:
57  friend class base::RefCountedThreadSafe<AudioOutputResampler>;
58  virtual ~AudioOutputResampler();
59
60  // Converts low latency based output parameters into high latency
61  // appropriate output parameters in error situations.
62  void SetupFallbackParams();
63
64  // Used to initialize and reinitialize |dispatcher_|.
65  void Initialize();
66
67  // Dispatcher to proxy all AudioOutputDispatcher calls too.
68  scoped_refptr<AudioOutputDispatcher> dispatcher_;
69
70  // Map of outstanding OnMoreDataConverter objects.  A new object is created
71  // on every StartStream() call and destroyed on CloseStream().
72  typedef std::map<AudioOutputProxy*, OnMoreDataConverter*> CallbackMap;
73  CallbackMap callbacks_;
74
75  // Used by AudioOutputDispatcherImpl; kept so we can reinitialize on the fly.
76  base::TimeDelta close_delay_;
77
78  // AudioParameters used to setup the output stream.
79  AudioParameters output_params_;
80
81  // Whether any streams have been opened through |dispatcher_|, if so we can't
82  // fallback on future OpenStream() failures.
83  bool streams_opened_;
84
85  DISALLOW_COPY_AND_ASSIGN(AudioOutputResampler);
86};
87
88}  // namespace media
89
90#endif  // MEDIA_AUDIO_AUDIO_OUTPUT_RESAMPLER_H_
91