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/*
* Copyright (C) 2010, 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.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. 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 INC. 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 AudioResamplerKernel_h
#define AudioResamplerKernel_h
#include "platform/PlatformExport.h"
#include "platform/audio/AudioArray.h"
namespace blink {
class AudioResampler;
// AudioResamplerKernel does resampling on a single mono channel.
// It uses a simple linear interpolation for good performance.
class PLATFORM_EXPORT AudioResamplerKernel {
public:
AudioResamplerKernel(AudioResampler*);
// getSourcePointer() should be called each time before process() is called.
// Given a number of frames to process (for subsequent call to process()), it returns a pointer and numberOfSourceFramesNeeded
// where sample data should be copied. This sample data provides the input to the resampler when process() is called.
// framesToProcess must be less than or equal to MaxFramesToProcess.
float* getSourcePointer(size_t framesToProcess, size_t* numberOfSourceFramesNeeded);
// process() resamples framesToProcess frames from the source into destination.
// Each call to process() must be preceded by a call to getSourcePointer() so that source input may be supplied.
// framesToProcess must be less than or equal to MaxFramesToProcess.
void process(float* destination, size_t framesToProcess);
// Resets the processing state.
void reset();
static const size_t MaxFramesToProcess;
private:
double rate() const;
AudioResampler* m_resampler;
AudioFloatArray m_sourceBuffer;
// This is a (floating point) read index on the input stream.
double m_virtualReadIndex;
// We need to have continuity from one call of process() to the next.
// m_lastValues stores the last two sample values from the last call to process().
// m_fillIndex represents how many buffered samples we have which can be as many as 2.
// For the first call to process() (or after reset()) there will be no buffered samples.
float m_lastValues[2];
unsigned m_fillIndex;
};
} // namespace blink
#endif // AudioResamplerKernel_h
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