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/base/audio_bus.h"
  15 #include "media/base/channel_layout.h"
  16 #include "media/base/media_export.h"
  17
  18 namespace media {
  19
  20 // Use a struct-in-struct approach to ensure that we can calculate the required
  21 // size as sizeof(AudioInputBufferParameters) + #(bytes in audio buffer) without
  22 // using packing. Also align AudioInputBufferParameters instead of in
  23 // AudioInputBuffer to be able to calculate size like so. Use a macro for the
  24 // alignment value that's the same as AudioBus::kChannelAlignment, since MSVC
  25 // doesn't accept the latter to be used.
  26 #if defined(OS_WIN)
  27 #pragma warning(push)
  28 #pragma warning(disable: 4324)  // Disable warning for added padding.
  29 #endif
  30 #define PARAMETERS_ALIGNMENT 16
  31 COMPILE_ASSERT(AudioBus::kChannelAlignment == PARAMETERS_ALIGNMENT,
  32                AudioInputBufferParameters_alignment_not_same_as_AudioBus);
  33 struct MEDIA_EXPORT ALIGNAS(PARAMETERS_ALIGNMENT) AudioInputBufferParameters {
  34   double volume;
  35   uint32 size;
  36   uint32_t hardware_delay_bytes;
  37   uint32_t id;
  38   bool key_pressed;
  39 };
  40 #undef PARAMETERS_ALIGNMENT
  41 #if defined(OS_WIN)
  42 #pragma warning(pop)
  43 #endif
  44
  45 COMPILE_ASSERT(
  46     sizeof(AudioInputBufferParameters) % AudioBus::kChannelAlignment == 0,
  47     AudioInputBufferParameters_not_aligned);
  48
  49 struct MEDIA_EXPORT AudioInputBuffer {
  50   AudioInputBufferParameters params;
  51   int8 audio[1];
  52 };
  53
  54 class MEDIA_EXPORT AudioParameters {
  55  public:
  56   // TODO(miu): Rename this enum to something that correctly reflects its
  57   // semantics, such as "TransportScheme."
  58   enum Format {
  59     AUDIO_PCM_LINEAR = 0,            // PCM is 'raw' amplitude samples.
  60     AUDIO_PCM_LOW_LATENCY,           // Linear PCM, low latency requested.
  61     AUDIO_FAKE,                      // Creates a fake AudioOutputStream object.
  62     AUDIO_FORMAT_LAST = AUDIO_FAKE,  // Only used for validation of format.
  63   };
  64
  65   enum {
  66     // Telephone quality sample rate, mostly for speech-only audio.
  67     kTelephoneSampleRate = 8000,
  68     // CD sampling rate is 44.1 KHz or conveniently 2x2x3x3x5x5x7x7.
  69     kAudioCDSampleRate = 44100,
  70   };
  71
  72   // Bitmasks to determine whether certain platform (typically hardware) audio
  73   // effects should be enabled.
  74   enum PlatformEffectsMask {
  75     NO_EFFECTS = 0x0,
  76     ECHO_CANCELLER = 0x1,
  77     DUCKING = 0x2,  // Enables ducking if the OS supports it.
  78     KEYBOARD_MIC = 0x4,
  79     HOTWORD = 0x8,
  80   };
  81
  82   AudioParameters();
  83   AudioParameters(Format format, ChannelLayout channel_layout,
  84                   int sample_rate, int bits_per_sample,
  85                   int frames_per_buffer);
  86   AudioParameters(Format format, ChannelLayout channel_layout,
  87                   int sample_rate, int bits_per_sample,
  88                   int frames_per_buffer, int effects);
  89   AudioParameters(Format format, ChannelLayout channel_layout,
  90                   int channels, int sample_rate, int bits_per_sample,
  91                   int frames_per_buffer, int effects);
  92
  93   void Reset(Format format, ChannelLayout channel_layout,
  94              int channels, int sample_rate, int bits_per_sample,
  95              int frames_per_buffer);
  96
  97   // Checks that all values are in the expected range. All limits are specified
  98   // in media::Limits.
  99   bool IsValid() const;
 100
 101   // Returns a human-readable string describing |*this|.  For debugging & test
 102   // output only.
 103   std::string AsHumanReadableString() const;
 104
 105   // Returns size of audio buffer in bytes.
 106   int GetBytesPerBuffer() const;
 107
 108   // Returns the number of bytes representing one second of audio.
 109   int GetBytesPerSecond() const;
 110
 111   // Returns the number of bytes representing a frame of audio.
 112   int GetBytesPerFrame() const;
 113
 114   // Returns the duration of this buffer as calculated from frames_per_buffer()
 115   // and sample_rate().
 116   base::TimeDelta GetBufferDuration() const;
 117
 118   // Comparison with other AudioParams.
 119   bool Equals(const AudioParameters& other) const;
 120
 121   Format format() const { return format_; }
 122   ChannelLayout channel_layout() const { return channel_layout_; }
 123   int sample_rate() const { return sample_rate_; }
 124   int bits_per_sample() const { return bits_per_sample_; }
 125   int frames_per_buffer() const { return frames_per_buffer_; }
 126   int channels() const { return channels_; }
 127   int effects() const { return effects_; }
 128
 129  private:
 130   // These members are mutable to support entire struct assignment. They should
 131   // not be mutated individually.
 132   Format format_;                 // Format of the stream.
 133   ChannelLayout channel_layout_;  // Order of surround sound channels.
 134   int sample_rate_;               // Sampling frequency/rate.
 135   int bits_per_sample_;           // Number of bits per sample.
 136   int frames_per_buffer_;         // Number of frames in a buffer.
 137
 138   int channels_;                  // Number of channels. Value set based on
 139                                   // |channel_layout|.
 140   int effects_;                   // Bitmask using PlatformEffectsMask.
 141 };
 142
 143 // Comparison is useful when AudioParameters is used with std structures.
 144 inline bool operator<(const AudioParameters& a, const AudioParameters& b) {
 145   if (a.format() != b.format())
 146     return a.format() < b.format();
 147   if (a.channels() != b.channels())
 148     return a.channels() < b.channels();
 149   if (a.sample_rate() != b.sample_rate())
 150     return a.sample_rate() < b.sample_rate();
 151   if (a.bits_per_sample() != b.bits_per_sample())
 152     return a.bits_per_sample() < b.bits_per_sample();
 153   return a.frames_per_buffer() < b.frames_per_buffer();
 154 }
 155
 156 }  // namespace media
 157
 158 #endif  // MEDIA_AUDIO_AUDIO_PARAMETERS_H_