media/audio/audio_parameters.h

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