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 "base/time/time.h"
  10 #include "media/base/channel_layout.h"
  11 #include "media/base/media_export.h"
  12
  13 namespace media {
  14
  15 struct 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.
  24 struct MEDIA_EXPORT AudioInputBuffer {
  25   AudioInputBufferParameters params;
  26   int8 audio[1];
  27 };
  28
  29 class 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 sample_rate, int bits_per_sample,
  62                   int frames_per_buffer, int effects);
  63   AudioParameters(Format format, ChannelLayout channel_layout,
  64                   int channels, int sample_rate, int bits_per_sample,
  65                   int frames_per_buffer, int effects);
  66
  67   void Reset(Format format, ChannelLayout channel_layout,
  68              int channels, int sample_rate, int bits_per_sample,
  69              int frames_per_buffer);
  70
  71   // Checks that all values are in the expected range. All limits are specified
  72   // in media::Limits.
  73   bool IsValid() const;
  74
  75   // Returns size of audio buffer in bytes.
  76   int GetBytesPerBuffer() const;
  77
  78   // Returns the number of bytes representing one second of audio.
  79   int GetBytesPerSecond() const;
  80
  81   // Returns the number of bytes representing a frame of audio.
  82   int GetBytesPerFrame() const;
  83
  84   // Returns the duration of this buffer as calculated from frames_per_buffer()
  85   // and sample_rate().
  86   base::TimeDelta GetBufferDuration() const;
  87
  88   // Comparison with other AudioParams.
  89   bool Equals(const AudioParameters& other) 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 effects() const { return effects_; }
  98
  99  private:
 100   // These members are mutable to support entire struct assignment. They should
 101   // not be mutated individually.
 102   Format format_;                 // Format of the stream.
 103   ChannelLayout channel_layout_;  // Order of surround sound channels.
 104   int sample_rate_;               // Sampling frequency/rate.
 105   int bits_per_sample_;           // Number of bits per sample.
 106   int frames_per_buffer_;         // Number of frames in a buffer.
 107
 108   int channels_;                  // Number of channels. Value set based on
 109                                   // |channel_layout|.
 110   int effects_;                   // Bitmask using PlatformEffectsMask.
 111 };
 112
 113 // Comparison is useful when AudioParameters is used with std structures.
 114 inline bool operator<(const AudioParameters& a, const AudioParameters& b) {
 115   if (a.format() != b.format())
 116     return a.format() < b.format();
 117   if (a.channels() != b.channels())
 118     return a.channels() < b.channels();
 119   if (a.sample_rate() != b.sample_rate())
 120     return a.sample_rate() < b.sample_rate();
 121   if (a.bits_per_sample() != b.bits_per_sample())
 122     return a.bits_per_sample() < b.bits_per_sample();
 123   return a.frames_per_buffer() < b.frames_per_buffer();
 124 }
 125
 126 }  // namespace media
 127
 128 #endif  // MEDIA_AUDIO_AUDIO_PARAMETERS_H_