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      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   };
     53 
     54   AudioParameters();
     55   AudioParameters(Format format, ChannelLayout channel_layout,
     56                   int sample_rate, int bits_per_sample,
     57                   int frames_per_buffer);
     58   AudioParameters(Format format, ChannelLayout channel_layout,
     59                   int input_channels,
     60                   int sample_rate, int bits_per_sample,
     61                   int frames_per_buffer, int effects);
     62   AudioParameters(Format format, ChannelLayout channel_layout,
     63                   int channels, int input_channels,
     64                   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 input_channels,
     69              int sample_rate, int bits_per_sample,
     70              int frames_per_buffer);
     71 
     72   // Checks that all values are in the expected range. All limits are specified
     73   // in media::Limits.
     74   bool IsValid() const;
     75 
     76   // Returns size of audio buffer in bytes.
     77   int GetBytesPerBuffer() const;
     78 
     79   // Returns the number of bytes representing one second of audio.
     80   int GetBytesPerSecond() const;
     81 
     82   // Returns the number of bytes representing a frame of audio.
     83   int GetBytesPerFrame() const;
     84 
     85   // Returns the duration of this buffer as calculated from frames_per_buffer()
     86   // and sample_rate().
     87   base::TimeDelta GetBufferDuration() const;
     88 
     89   Format format() const { return format_; }
     90   ChannelLayout channel_layout() const { return channel_layout_; }
     91   int sample_rate() const { return sample_rate_; }
     92   int bits_per_sample() const { return bits_per_sample_; }
     93   int frames_per_buffer() const { return frames_per_buffer_; }
     94   int channels() const { return channels_; }
     95   int input_channels() const { return input_channels_; }
     96   int effects() const { return effects_; }
     97 
     98   // Comparison with other AudioParams.
     99   bool operator==(const AudioParameters& other) const {
    100     return format_ == other.format() &&
    101            sample_rate_ == other.sample_rate() &&
    102            channel_layout_ == other.channel_layout() &&
    103            channels_ == other.channels() &&
    104            input_channels_ == other.input_channels() &&
    105            bits_per_sample_ == other.bits_per_sample() &&
    106            frames_per_buffer_ == other.frames_per_buffer() &&
    107            effects_ == other.effects();
    108   }
    109 
    110  private:
    111   // These members are mutable to support entire struct assignment. They should
    112   // not be mutated individually.
    113   Format format_;                 // Format of the stream.
    114   ChannelLayout channel_layout_;  // Order of surround sound channels.
    115   int sample_rate_;               // Sampling frequency/rate.
    116   int bits_per_sample_;           // Number of bits per sample.
    117   int frames_per_buffer_;         // Number of frames in a buffer.
    118 
    119   int channels_;                  // Number of channels. Value set based on
    120                                   // |channel_layout|.
    121   int input_channels_;            // Optional number of input channels.
    122                                   // Normally 0, but can be set to specify
    123                                   // synchronized I/O.
    124   int effects_;                   // Bitmask using PlatformEffectsMask.
    125 };
    126 
    127 // Comparison is useful when AudioParameters is used with std structures.
    128 inline bool operator<(const AudioParameters& a, const AudioParameters& b) {
    129   if (a.format() != b.format())
    130     return a.format() < b.format();
    131   if (a.channels() != b.channels())
    132     return a.channels() < b.channels();
    133   if (a.input_channels() != b.input_channels())
    134     return a.input_channels() < b.input_channels();
    135   if (a.sample_rate() != b.sample_rate())
    136     return a.sample_rate() < b.sample_rate();
    137   if (a.bits_per_sample() != b.bits_per_sample())
    138     return a.bits_per_sample() < b.bits_per_sample();
    139   return a.frames_per_buffer() < b.frames_per_buffer();
    140 }
    141 
    142 }  // namespace media
    143 
    144 #endif  // MEDIA_AUDIO_AUDIO_PARAMETERS_H_
    145