audio_parameters.h revision 1e9bf3e0803691d0a228da41fc608347b6db4340 
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_PARAMETERS_H_
6#define MEDIA_AUDIO_AUDIO_PARAMETERS_H_
7
8#include "base/basictypes.h"
9#include "base/time/time.h"
10#include "media/base/channel_layout.h"
11#include "media/base/media_export.h"
12
13namespace media {
14
15struct MEDIA_EXPORT AudioInputBufferParameters {
16  double volume;
17  uint32 size;
18  bool key_pressed;
19};
20
21// Use a struct-in-struct approach to ensure that we can calculate the required
22// size as sizeof(AudioInputBufferParameters) + #(bytes in audio buffer) without
23// using packing.
24struct MEDIA_EXPORT AudioInputBuffer {
25  AudioInputBufferParameters params;
26  int8 audio[1];
27};
28
29class MEDIA_EXPORT AudioParameters {
30 public:
31  // TODO(miu): Rename this enum to something that correctly reflects its
32  // semantics, such as "TransportScheme."
33  enum Format {
34    AUDIO_PCM_LINEAR = 0,     // PCM is 'raw' amplitude samples.
35    AUDIO_PCM_LOW_LATENCY,    // Linear PCM, low latency requested.
36    AUDIO_FAKE,               // Creates a fake AudioOutputStream object.
37    AUDIO_LAST_FORMAT         // Only used for validation of format.
38  };
39
40  enum {
41    // Telephone quality sample rate, mostly for speech-only audio.
42    kTelephoneSampleRate = 8000,
43    // CD sampling rate is 44.1 KHz or conveniently 2x2x3x3x5x5x7x7.
44    kAudioCDSampleRate = 44100,
45  };
46
47  AudioParameters();
48  AudioParameters(Format format, ChannelLayout channel_layout,
49                  int sample_rate, int bits_per_sample,
50                  int frames_per_buffer);
51  AudioParameters(Format format, ChannelLayout channel_layout,
52                  int input_channels,
53                  int sample_rate, int bits_per_sample,
54                  int frames_per_buffer);
55  void Reset(Format format, ChannelLayout channel_layout,
56             int channels, int input_channels,
57             int sample_rate, int bits_per_sample,
58             int frames_per_buffer);
59
60  // Checks that all values are in the expected range. All limits are specified
61  // in media::Limits.
62  bool IsValid() const;
63
64  // Returns size of audio buffer in bytes.
65  int GetBytesPerBuffer() const;
66
67  // Returns the number of bytes representing one second of audio.
68  int GetBytesPerSecond() const;
69
70  // Returns the number of bytes representing a frame of audio.
71  int GetBytesPerFrame() const;
72
73  // Returns the duration of this buffer as calculated from frames_per_buffer()
74  // and sample_rate().
75  base::TimeDelta GetBufferDuration() const;
76
77  Format format() const { return format_; }
78  ChannelLayout channel_layout() const { return channel_layout_; }
79  int sample_rate() const { return sample_rate_; }
80  int bits_per_sample() const { return bits_per_sample_; }
81  int frames_per_buffer() const { return frames_per_buffer_; }
82  int channels() const { return channels_; }
83  int input_channels() const { return input_channels_; }
84
85  // Set to CHANNEL_LAYOUT_DISCRETE with given number of channels.
86  void SetDiscreteChannels(int channels);
87
88  // Comparison with other AudioParams.
89  bool operator==(const AudioParameters& other) const {
90    return format_ == other.format() &&
91           sample_rate_ == other.sample_rate() &&
92           channel_layout_ == other.channel_layout() &&
93           channels_ == other.channels() &&
94           input_channels_ == other.input_channels() &&
95           bits_per_sample_ == other.bits_per_sample() &&
96           frames_per_buffer_ == other.frames_per_buffer();
97  }
98
99 private:
100  Format format_;                 // Format of the stream.
101  ChannelLayout channel_layout_;  // Order of surround sound channels.
102  int sample_rate_;               // Sampling frequency/rate.
103  int bits_per_sample_;           // Number of bits per sample.
104  int frames_per_buffer_;         // Number of frames in a buffer.
105
106  int channels_;                  // Number of channels. Value set based on
107                                  // |channel_layout|.
108  int input_channels_;            // Optional number of input channels.
109                                  // Normally 0, but can be set to specify
110                                  // synchronized I/O.
111};
112
113// Comparison is useful when AudioParameters is used with std structures.
114inline bool operator<(const AudioParameters& a, const AudioParameters& b) {
115  if (a.format() != b.format())
116    return a.format() < b.format();
117  if (a.channels() != b.channels())
118    return a.channels() < b.channels();
119  if (a.input_channels() != b.input_channels())
120    return a.input_channels() < b.input_channels();
121  if (a.sample_rate() != b.sample_rate())
122    return a.sample_rate() < b.sample_rate();
123  if (a.bits_per_sample() != b.bits_per_sample())
124    return a.bits_per_sample() < b.bits_per_sample();
125  return a.frames_per_buffer() < b.frames_per_buffer();
126}
127
128}  // namespace media
129
130#endif  // MEDIA_AUDIO_AUDIO_PARAMETERS_H_
131