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/*
* Copyright (C) 2011 Google Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of Apple Computer, Inc. ("Apple") nor the names of
* its contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef SincResampler_h
#define SincResampler_h
#include "platform/PlatformExport.h"
#include "platform/audio/AudioArray.h"
#include "platform/audio/AudioSourceProvider.h"
#include "wtf/Allocator.h"
#include "wtf/Noncopyable.h"
namespace blink {
// SincResampler is a high-quality sample-rate converter.
class PLATFORM_EXPORT SincResampler {
USING_FAST_MALLOC(SincResampler);
WTF_MAKE_NONCOPYABLE(SincResampler);
public:
// scaleFactor == sourceSampleRate / destinationSampleRate
// kernelSize can be adjusted for quality (higher is better)
// numberOfKernelOffsets is used for interpolation and is the number of sub-sample kernel shifts.
SincResampler(double scaleFactor, unsigned kernelSize = 32, unsigned numberOfKernelOffsets = 32);
// Processes numberOfSourceFrames from source to produce numberOfSourceFrames / scaleFactor frames in destination.
void process(const float* source, float* destination, unsigned numberOfSourceFrames);
// Process with input source callback function for streaming applications.
void process(AudioSourceProvider*, float* destination, size_t framesToProcess);
protected:
void initializeKernel();
void consumeSource(float* buffer, unsigned numberOfSourceFrames);
double m_scaleFactor;
unsigned m_kernelSize;
unsigned m_numberOfKernelOffsets;
// m_kernelStorage has m_numberOfKernelOffsets kernels back-to-back, each of size m_kernelSize.
// The kernel offsets are sub-sample shifts of a windowed sinc() shifted from 0.0 to 1.0 sample.
AudioFloatArray m_kernelStorage;
// m_virtualSourceIndex is an index on the source input buffer with sub-sample precision.
// It must be double precision to avoid drift.
double m_virtualSourceIndex;
// This is the number of destination frames we generate per processing pass on the buffer.
unsigned m_blockSize;
// Source is copied into this buffer for each processing pass.
AudioFloatArray m_inputBuffer;
const float* m_source;
unsigned m_sourceFramesAvailable;
// m_sourceProvider is used to provide the audio input stream to the resampler.
AudioSourceProvider* m_sourceProvider;
// The buffer is primed once at the very beginning of processing.
bool m_isBufferPrimed;
};
} // namespace blink
#endif // SincResampler_h
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