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