audio_parameters.h revision 5d1f7b1de12d16ceb2c938c56701a3e8bfa558f7 
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  // Bitmasks to determine whether certain platform (typically hardware) audio
48  // effects should be enabled.
49  enum PlatformEffectsMask {
50    NO_EFFECTS = 0x0,
51    ECHO_CANCELLER = 0x1,
52    DUCKING = 0x2,  // Enables ducking if the OS supports it.
53  };
54
55  AudioParameters();
56  AudioParameters(Format format, ChannelLayout channel_layout,
57                  int sample_rate, int bits_per_sample,
58                  int frames_per_buffer);
59  AudioParameters(Format format, ChannelLayout channel_layout,
60                  int input_channels,
61                  int sample_rate, int bits_per_sample,
62                  int frames_per_buffer, int effects);
63  AudioParameters(Format format, ChannelLayout channel_layout,
64                  int channels, int input_channels,
65                  int sample_rate, int bits_per_sample,
66                  int frames_per_buffer, int effects);
67
68  void Reset(Format format, ChannelLayout channel_layout,
69             int channels, int input_channels,
70             int sample_rate, int bits_per_sample,
71             int frames_per_buffer);
72
73  // Checks that all values are in the expected range. All limits are specified
74  // in media::Limits.
75  bool IsValid() const;
76
77  // Returns size of audio buffer in bytes.
78  int GetBytesPerBuffer() const;
79
80  // Returns the number of bytes representing one second of audio.
81  int GetBytesPerSecond() const;
82
83  // Returns the number of bytes representing a frame of audio.
84  int GetBytesPerFrame() const;
85
86  // Returns the duration of this buffer as calculated from frames_per_buffer()
87  // and sample_rate().
88  base::TimeDelta GetBufferDuration() const;
89
90  Format format() const { return format_; }
91  ChannelLayout channel_layout() const { return channel_layout_; }
92  int sample_rate() const { return sample_rate_; }
93  int bits_per_sample() const { return bits_per_sample_; }
94  int frames_per_buffer() const { return frames_per_buffer_; }
95  int channels() const { return channels_; }
96  int input_channels() const { return input_channels_; }
97  int effects() const { return effects_; }
98
99  // Comparison with other AudioParams.
100  bool operator==(const AudioParameters& other) const {
101    return format_ == other.format() &&
102           sample_rate_ == other.sample_rate() &&
103           channel_layout_ == other.channel_layout() &&
104           channels_ == other.channels() &&
105           input_channels_ == other.input_channels() &&
106           bits_per_sample_ == other.bits_per_sample() &&
107           frames_per_buffer_ == other.frames_per_buffer() &&
108           effects_ == other.effects();
109  }
110
111 private:
112  // These members are mutable to support entire struct assignment. They should
113  // not be mutated individually.
114  Format format_;                 // Format of the stream.
115  ChannelLayout channel_layout_;  // Order of surround sound channels.
116  int sample_rate_;               // Sampling frequency/rate.
117  int bits_per_sample_;           // Number of bits per sample.
118  int frames_per_buffer_;         // Number of frames in a buffer.
119
120  int channels_;                  // Number of channels. Value set based on
121                                  // |channel_layout|.
122  int input_channels_;            // Optional number of input channels.
123                                  // Normally 0, but can be set to specify
124                                  // synchronized I/O.
125  int effects_;                   // Bitmask using PlatformEffectsMask.
126};
127
128// Comparison is useful when AudioParameters is used with std structures.
129inline bool operator<(const AudioParameters& a, const AudioParameters& b) {
130  if (a.format() != b.format())
131    return a.format() < b.format();
132  if (a.channels() != b.channels())
133    return a.channels() < b.channels();
134  if (a.input_channels() != b.input_channels())
135    return a.input_channels() < b.input_channels();
136  if (a.sample_rate() != b.sample_rate())
137    return a.sample_rate() < b.sample_rate();
138  if (a.bits_per_sample() != b.bits_per_sample())
139    return a.bits_per_sample() < b.bits_per_sample();
140  return a.frames_per_buffer() < b.frames_per_buffer();
141}
142
143}  // namespace media
144
145#endif  // MEDIA_AUDIO_AUDIO_PARAMETERS_H_
146