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// Copyright (c) 2009 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.
#ifndef MEDIA_AUDIO_AUDIO_UTIL_H_
#define MEDIA_AUDIO_AUDIO_UTIL_H_
#include "base/basictypes.h"
namespace media {
// For all audio functions 3 audio formats are supported:
// 8 bits unsigned 0 to 255.
// 16 bit signed (little endian).
// 32 bit signed (little endian)
// AdjustVolume() does a software volume adjustment of a sample buffer.
// The samples are multiplied by the volume, which should range from
// 0.0 (mute) to 1.0 (full volume).
// Using software allows each audio and video to have its own volume without
// affecting the master volume.
// In the future the function may be used to adjust the sample format to
// simplify hardware requirements and to support a wider variety of input
// formats.
// The buffer is modified in-place to avoid memory management, as this
// function may be called in performance critical code.
bool AdjustVolume(void* buf,
size_t buflen,
int channels,
int bytes_per_sample,
float volume);
// FoldChannels() does a software multichannel folding down to stereo.
// Channel order is assumed to be 5.1 Dolby standard which is
// front left, front right, center, surround left, surround right.
// The subwoofer is ignored.
// 6.1 adds a rear center speaker, and 7.1 has 2 rear speakers. These
// channels are rare and ignored.
// After summing the channels, volume is adjusted and the samples are
// clipped to the maximum value.
// Volume should normally range from 0.0 (mute) to 1.0 (full volume), but
// since clamping is performed a value of more than 1 is allowed to increase
// volume.
// The buffer is modified in-place to avoid memory management, as this
// function may be called in performance critical code.
bool FoldChannels(void* buf,
size_t buflen,
int channels,
int bytes_per_sample,
float volume);
} // namespace media
#endif // MEDIA_AUDIO_AUDIO_UTIL_H_
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