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 format()91 Format format() const { return format_; } channel_layout()92 ChannelLayout channel_layout() const { return channel_layout_; } sample_rate()93 int sample_rate() const { return sample_rate_; } bits_per_sample()94 int bits_per_sample() const { return bits_per_sample_; } frames_per_buffer()95 int frames_per_buffer() const { return frames_per_buffer_; } channels()96 int channels() const { return channels_; } effects()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_ 129