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   // Compare is useful when AudioParameters is used as a key in std::map.
  30   class MEDIA_EXPORT Compare {
  31    public:
  32     bool operator()(const AudioParameters& a, const AudioParameters& b) const;
  33   };
  34
  35   enum Format {
  36     AUDIO_PCM_LINEAR = 0,     // PCM is 'raw' amplitude samples.
  37     AUDIO_PCM_LOW_LATENCY,    // Linear PCM, low latency requested.
  38     AUDIO_MOCK,               // Creates a dummy AudioOutputStream object.
  39     AUDIO_LAST_FORMAT         // Only used for validation of format.y
  40   };
  41
  42   // Telephone quality sample rate, mostly for speech-only audio.
  43   static const uint32 kTelephoneSampleRate = 8000;
  44   // CD sampling rate is 44.1 KHz or conveniently 2x2x3x3x5x5x7x7.
  45   static const uint32 kAudioCDSampleRate = 44100;
  46   // Digital Audio Tape sample rate.
  47   static const uint32 kAudioDATSampleRate = 48000;
  48
  49   AudioParameters();
  50   AudioParameters(Format format, ChannelLayout channel_layout,
  51                   int sample_rate, int bits_per_sample,
  52                   int frames_per_buffer);
  53   void Reset(Format format, ChannelLayout channel_layout,
  54              int sample_rate, int bits_per_sample,
  55              int frames_per_buffer);
  56
  57   // Checks that all values are in the expected range. All limits are specified
  58   // in media::Limits.
  59   bool IsValid() const;
  60
  61   // Returns size of audio buffer in bytes.
  62   int GetBytesPerBuffer() const;
  63
  64   // Returns the number of bytes representing one second of audio.
  65   int GetBytesPerSecond() const;
  66
  67   // Returns the number of bytes representing a frame of audio.
  68   int GetBytesPerFrame() const;
  69
  70   Format format() const { return format_; }
  71   ChannelLayout channel_layout() const { return channel_layout_; }
  72   int sample_rate() const { return sample_rate_; }
  73   int bits_per_sample() const { return bits_per_sample_; }
  74   int frames_per_buffer() const { return frames_per_buffer_; }
  75   int channels() const { return channels_; }
  76
  77  private:
  78   Format format_;                 // Format of the stream.
  79   ChannelLayout channel_layout_;  // Order of surround sound channels.
  80   int sample_rate_;               // Sampling frequency/rate.
  81   int bits_per_sample_;           // Number of bits per sample.
  82   int frames_per_buffer_;         // Number of frames in a buffer.
  83
  84   int channels_;                  // Number of channels. Value set based on
  85                                   // |channel_layout|.
  86 };
  87
  88 }  // namespace media
  89
  90 #endif  // MEDIA_AUDIO_AUDIO_PARAMETERS_H_