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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/basictypes.h"
#include "base/time/time.h"
#include "media/base/channel_layout.h"
#include "media/base/media_export.h"
namespace media {
struct MEDIA_EXPORT AudioInputBufferParameters {
double volume;
uint32 size;
bool key_pressed;
// Use a struct-in-struct approach to ensure that we can calculate the required
// size as sizeof(AudioInputBufferParameters) + #(bytes in audio buffer) without
// using packing.
struct MEDIA_EXPORT AudioInputBuffer {
AudioInputBufferParameters params;
int8 audio[1];
class MEDIA_EXPORT AudioParameters {
// TODO(miu): Rename this enum to something that correctly reflects its
// semantics, such as "TransportScheme."
enum Format {
AUDIO_PCM_LINEAR = 0, // PCM is 'raw' amplitude samples.
AUDIO_PCM_LOW_LATENCY, // Linear PCM, low latency requested.
AUDIO_FAKE, // Creates a fake AudioOutputStream object.
AUDIO_LAST_FORMAT // Only used for validation of format.
enum {
// Telephone quality sample rate, mostly for speech-only audio.
kTelephoneSampleRate = 8000,
// CD sampling rate is 44.1 KHz or conveniently 2x2x3x3x5x5x7x7.
kAudioCDSampleRate = 44100,
AudioParameters(Format format, ChannelLayout channel_layout,
int sample_rate, int bits_per_sample,
int frames_per_buffer);
AudioParameters(Format format, ChannelLayout channel_layout,
int input_channels,
int sample_rate, int bits_per_sample,
int frames_per_buffer);
void Reset(Format format, ChannelLayout channel_layout,
int channels, int input_channels,
int sample_rate, int bits_per_sample,
int frames_per_buffer);
// Checks that all values are in the expected range. All limits are specified
// in media::Limits.
bool IsValid() const;
// Returns size of audio buffer in bytes.
int GetBytesPerBuffer() const;
// Returns the number of bytes representing one second of audio.
int GetBytesPerSecond() const;
// Returns the number of bytes representing a frame of audio.
int GetBytesPerFrame() const;
// Returns the duration of this buffer as calculated from frames_per_buffer()
// and sample_rate().
base::TimeDelta GetBufferDuration() const;
Format format() const { return format_; }
ChannelLayout channel_layout() const { return channel_layout_; }
int sample_rate() const { return sample_rate_; }
int bits_per_sample() const { return bits_per_sample_; }
int frames_per_buffer() const { return frames_per_buffer_; }
int channels() const { return channels_; }
int input_channels() const { return input_channels_; }
// Set to CHANNEL_LAYOUT_DISCRETE with given number of channels.
void SetDiscreteChannels(int channels);
// Comparison with other AudioParams.
bool operator==(const AudioParameters& other) const {
return format_ == other.format() &&
sample_rate_ == other.sample_rate() &&
channel_layout_ == other.channel_layout() &&
channels_ == other.channels() &&
input_channels_ == other.input_channels() &&
bits_per_sample_ == other.bits_per_sample() &&
frames_per_buffer_ == other.frames_per_buffer();
Format format_; // Format of the stream.
ChannelLayout channel_layout_; // Order of surround sound channels.
int sample_rate_; // Sampling frequency/rate.
int bits_per_sample_; // Number of bits per sample.
int frames_per_buffer_; // Number of frames in a buffer.
int channels_; // Number of channels. Value set based on
// |channel_layout|.
int input_channels_; // Optional number of input channels.
// Normally 0, but can be set to specify
// synchronized I/O.
// Comparison is useful when AudioParameters is used with std structures.
inline bool operator<(const AudioParameters& a, const AudioParameters& b) {
if (a.format() != b.format())
return a.format() < b.format();
if (a.channels() != b.channels())
return a.channels() < b.channels();
if (a.input_channels() != b.input_channels())
return a.input_channels() < b.input_channels();
if (a.sample_rate() != b.sample_rate())
return a.sample_rate() < b.sample_rate();
if (a.bits_per_sample() != b.bits_per_sample())
return a.bits_per_sample() < b.bits_per_sample();
return a.frames_per_buffer() < b.frames_per_buffer();
} // namespace media