audio_parameters.h revision 23730a6e56a168d1879203e4b3819bb36e3d8f1f 
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    KEYBOARD_MIC = 0x4,
54  };
55
56  AudioParameters();
57  AudioParameters(Format format, ChannelLayout channel_layout,
58                  int sample_rate, int bits_per_sample,
59                  int frames_per_buffer);
60  AudioParameters(Format format, ChannelLayout channel_layout,
61                  int input_channels,
62                  int sample_rate, int bits_per_sample,
63                  int frames_per_buffer, int effects);
64  AudioParameters(Format format, ChannelLayout channel_layout,
65                  int channels, int input_channels,
66                  int sample_rate, int bits_per_sample,
67                  int frames_per_buffer, int effects);
68
69  void Reset(Format format, ChannelLayout channel_layout,
70             int channels, int input_channels,
71             int sample_rate, int bits_per_sample,
72             int frames_per_buffer);
73
74  // Checks that all values are in the expected range. All limits are specified
75  // in media::Limits.
76  bool IsValid() const;
77
78  // Returns size of audio buffer in bytes.
79  int GetBytesPerBuffer() const;
80
81  // Returns the number of bytes representing one second of audio.
82  int GetBytesPerSecond() const;
83
84  // Returns the number of bytes representing a frame of audio.
85  int GetBytesPerFrame() const;
86
87  // Returns the duration of this buffer as calculated from frames_per_buffer()
88  // and sample_rate().
89  base::TimeDelta GetBufferDuration() const;
90
91  Format format() const { return format_; }
92  ChannelLayout channel_layout() const { return channel_layout_; }
93  int sample_rate() const { return sample_rate_; }
94  int bits_per_sample() const { return bits_per_sample_; }
95  int frames_per_buffer() const { return frames_per_buffer_; }
96  int channels() const { return channels_; }
97  int input_channels() const { return input_channels_; }
98  int effects() const { return effects_; }
99
100  // Comparison with other AudioParams.
101  bool operator==(const AudioParameters& other) const {
102    return format_ == other.format() &&
103           sample_rate_ == other.sample_rate() &&
104           channel_layout_ == other.channel_layout() &&
105           channels_ == other.channels() &&
106           input_channels_ == other.input_channels() &&
107           bits_per_sample_ == other.bits_per_sample() &&
108           frames_per_buffer_ == other.frames_per_buffer() &&
109           effects_ == other.effects();
110  }
111
112 private:
113  // These members are mutable to support entire struct assignment. They should
114  // not be mutated individually.
115  Format format_;                 // Format of the stream.
116  ChannelLayout channel_layout_;  // Order of surround sound channels.
117  int sample_rate_;               // Sampling frequency/rate.
118  int bits_per_sample_;           // Number of bits per sample.
119  int frames_per_buffer_;         // Number of frames in a buffer.
120
121  int channels_;                  // Number of channels. Value set based on
122                                  // |channel_layout|.
123  int input_channels_;            // Optional number of input channels.
124                                  // Normally 0, but can be set to specify
125                                  // synchronized I/O.
126  int effects_;                   // Bitmask using PlatformEffectsMask.
127};
128
129// Comparison is useful when AudioParameters is used with std structures.
130inline bool operator<(const AudioParameters& a, const AudioParameters& b) {
131  if (a.format() != b.format())
132    return a.format() < b.format();
133  if (a.channels() != b.channels())
134    return a.channels() < b.channels();
135  if (a.input_channels() != b.input_channels())
136    return a.input_channels() < b.input_channels();
137  if (a.sample_rate() != b.sample_rate())
138    return a.sample_rate() < b.sample_rate();
139  if (a.bits_per_sample() != b.bits_per_sample())
140    return a.bits_per_sample() < b.bits_per_sample();
141  return a.frames_per_buffer() < b.frames_per_buffer();
142}
143
144}  // namespace media
145
146#endif  // MEDIA_AUDIO_AUDIO_PARAMETERS_H_
147