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/*
* Copyright (C) 2013 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 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 UpSampler_h
#define UpSampler_h
#include "AudioArray.h"
#include "DirectConvolver.h"
namespace WebCore {
// UpSampler up-samples the source stream by a factor of 2x.
class UpSampler {
public:
UpSampler(size_t inputBlockSize);
// The destination buffer |destP| is of size sourceFramesToProcess * 2.
void process(const float* sourceP, float* destP, size_t sourceFramesToProcess);
void reset();
// Latency based on the source sample-rate.
size_t latencyFrames() const;
private:
enum { DefaultKernelSize = 128 };
size_t m_inputBlockSize;
// Computes ideal band-limited filter coefficients to sample in between each source sample-frame.
// This filter will be used to compute the odd sample-frames of the output.
void initializeKernel();
AudioFloatArray m_kernel;
// Computes the odd sample-frames of the output.
DirectConvolver m_convolver;
AudioFloatArray m_tempBuffer;
// Delay line for generating the even sample-frames of the output.
// The source samples are delayed exactly to match the linear phase delay of the FIR filter (convolution)
// used to generate the odd sample-frames of the output.
AudioFloatArray m_inputBuffer;
};
} // namespace WebCore
#endif // UpSampler_h
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