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