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 <stdint.h>
   9 #include <string>
  10
  11 #include "base/basictypes.h"
  12 #include "base/compiler_specific.h"
  13 #include "base/time/time.h"
  14 #include "media/audio/point.h"
  15 #include "media/base/audio_bus.h"
  16 #include "media/base/channel_layout.h"
  17 #include "media/base/media_export.h"
  18
  19 namespace media {
  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. Also align AudioInputBufferParameters instead of in
  24 // AudioInputBuffer to be able to calculate size like so. Use a macro for the
  25 // alignment value that's the same as AudioBus::kChannelAlignment, since MSVC
  26 // doesn't accept the latter to be used.
  27 #if defined(OS_WIN)
  28 #pragma warning(push)
  29 #pragma warning(disable: 4324)  // Disable warning for added padding.
  30 #endif
  31 #define PARAMETERS_ALIGNMENT 16
  32 COMPILE_ASSERT(AudioBus::kChannelAlignment == PARAMETERS_ALIGNMENT,
  33                AudioInputBufferParameters_alignment_not_same_as_AudioBus);
  34 struct MEDIA_EXPORT ALIGNAS(PARAMETERS_ALIGNMENT) AudioInputBufferParameters {
  35   double volume;
  36   uint32 size;
  37   uint32_t hardware_delay_bytes;
  38   uint32_t id;
  39   bool key_pressed;
  40 };
  41 #undef PARAMETERS_ALIGNMENT
  42 #if defined(OS_WIN)
  43 #pragma warning(pop)
  44 #endif
  45
  46 COMPILE_ASSERT(
  47     sizeof(AudioInputBufferParameters) % AudioBus::kChannelAlignment == 0,
  48     AudioInputBufferParameters_not_aligned);
  49
  50 struct MEDIA_EXPORT AudioInputBuffer {
  51   AudioInputBufferParameters params;
  52   int8 audio[1];
  53 };
  54
  55 class MEDIA_EXPORT AudioParameters {
  56  public:
  57   // TODO(miu): Rename this enum to something that correctly reflects its
  58   // semantics, such as "TransportScheme."
  59   enum Format {
  60     AUDIO_PCM_LINEAR = 0,            // PCM is 'raw' amplitude samples.
  61     AUDIO_PCM_LOW_LATENCY,           // Linear PCM, low latency requested.
  62     AUDIO_FAKE,                      // Creates a fake AudioOutputStream object.
  63     AUDIO_FORMAT_LAST = AUDIO_FAKE,  // Only used for validation of format.
  64   };
  65
  66   enum {
  67     // Telephone quality sample rate, mostly for speech-only audio.
  68     kTelephoneSampleRate = 8000,
  69     // CD sampling rate is 44.1 KHz or conveniently 2x2x3x3x5x5x7x7.
  70     kAudioCDSampleRate = 44100,
  71   };
  72
  73   // Bitmasks to determine whether certain platform (typically hardware) audio
  74   // effects should be enabled.
  75   enum PlatformEffectsMask {
  76     NO_EFFECTS = 0x0,
  77     ECHO_CANCELLER = 0x1,
  78     DUCKING = 0x2,  // Enables ducking if the OS supports it.
  79     KEYBOARD_MIC = 0x4,
  80     HOTWORD = 0x8,
  81   };
  82
  83   AudioParameters();
  84   AudioParameters(Format format,
  85                   ChannelLayout channel_layout,
  86                   int sample_rate,
  87                   int bits_per_sample,
  88                   int frames_per_buffer);
  89
  90   ~AudioParameters();
  91
  92   // Re-initializes all members.
  93   void Reset(Format format,
  94              ChannelLayout channel_layout,
  95              int sample_rate,
  96              int bits_per_sample,
  97              int frames_per_buffer);
  98
  99   // Checks that all values are in the expected range. All limits are specified
 100   // in media::Limits.
 101   bool IsValid() const;
 102
 103   // Returns a human-readable string describing |*this|.  For debugging & test
 104   // output only.
 105   std::string AsHumanReadableString() const;
 106
 107   // Returns size of audio buffer in bytes.
 108   int GetBytesPerBuffer() const;
 109
 110   // Returns the number of bytes representing one second of audio.
 111   int GetBytesPerSecond() const;
 112
 113   // Returns the number of bytes representing a frame of audio.
 114   int GetBytesPerFrame() const;
 115
 116   // Returns the duration of this buffer as calculated from frames_per_buffer()
 117   // and sample_rate().
 118   base::TimeDelta GetBufferDuration() const;
 119
 120   // Comparison with other AudioParams.
 121   bool Equals(const AudioParameters& other) const;
 122
 123   void set_format(Format format) { format_ = format; }
 124   Format format() const { return format_; }
 125
 126   // A setter for channel_layout_ is intentionally excluded.
 127   ChannelLayout channel_layout() const { return channel_layout_; }
 128
 129   // The number of channels is usually computed from channel_layout_. Setting
 130   // this explictly is only required with CHANNEL_LAYOUT_DISCRETE.
 131   void set_channels_for_discrete(int channels) {
 132     DCHECK(channel_layout_ == CHANNEL_LAYOUT_DISCRETE ||
 133            channels == ChannelLayoutToChannelCount(channel_layout_));
 134     channels_ = channels;
 135   }
 136   int channels() const { return channels_; }
 137
 138   void set_sample_rate(int sample_rate) { sample_rate_ = sample_rate; }
 139   int sample_rate() const { return sample_rate_; }
 140
 141   void set_bits_per_sample(int bits_per_sample) {
 142     bits_per_sample_ = bits_per_sample;
 143   }
 144   int bits_per_sample() const { return bits_per_sample_; }
 145
 146   void set_frames_per_buffer(int frames_per_buffer) {
 147     frames_per_buffer_ = frames_per_buffer;
 148   }
 149   int frames_per_buffer() const { return frames_per_buffer_; }
 150
 151   void set_effects(int effects) { effects_ = effects; }
 152   int effects() const { return effects_; }
 153
 154   void set_mic_positions(const std::vector<Point>& mic_positions) {
 155     mic_positions_ = mic_positions;
 156   }
 157   const std::vector<Point>& mic_positions() const { return mic_positions_; }
 158
 159   AudioParameters(const AudioParameters&);
 160   AudioParameters& operator=(const AudioParameters&);
 161
 162  private:
 163   Format format_;                 // Format of the stream.
 164   ChannelLayout channel_layout_;  // Order of surround sound channels.
 165   int channels_;                  // Number of channels. Value set based on
 166                                   // |channel_layout|.
 167   int sample_rate_;               // Sampling frequency/rate.
 168   int bits_per_sample_;           // Number of bits per sample.
 169   int frames_per_buffer_;         // Number of frames in a buffer.
 170   int effects_;                   // Bitmask using PlatformEffectsMask.
 171
 172   // Microphone positions using Cartesian coordinates:
 173   // x: the horizontal dimension, with positive to the right from the camera's
 174   //    perspective.
 175   // y: the depth dimension, with positive forward from the camera's
 176   //    perspective.
 177   // z: the vertical dimension, with positive upwards.
 178   //
 179   // Usually, the center of the microphone array will be treated as the origin
 180   // (often the position of the camera).
 181   //
 182   // An empty vector indicates unknown positions.
 183   std::vector<Point> mic_positions_;
 184 };
 185
 186 // Comparison is useful when AudioParameters is used with std structures.
 187 inline bool operator<(const AudioParameters& a, const AudioParameters& b) {
 188   if (a.format() != b.format())
 189     return a.format() < b.format();
 190   if (a.channels() != b.channels())
 191     return a.channels() < b.channels();
 192   if (a.sample_rate() != b.sample_rate())
 193     return a.sample_rate() < b.sample_rate();
 194   if (a.bits_per_sample() != b.bits_per_sample())
 195     return a.bits_per_sample() < b.bits_per_sample();
 196   return a.frames_per_buffer() < b.frames_per_buffer();
 197 }
 198
 199 }  // namespace media
 200
 201 #endif  // MEDIA_AUDIO_AUDIO_PARAMETERS_H_