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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.
*/
#include "config.h"
#if ENABLE(WEB_AUDIO)
#include "UpSampler.h"
#include <wtf/MathExtras.h>
namespace WebCore {
UpSampler::UpSampler(size_t inputBlockSize)
: m_inputBlockSize(inputBlockSize)
, m_kernel(DefaultKernelSize)
, m_convolver(inputBlockSize)
, m_tempBuffer(inputBlockSize)
, m_inputBuffer(inputBlockSize * 2)
{
initializeKernel();
}
void UpSampler::initializeKernel()
{
// Blackman window parameters.
double alpha = 0.16;
double a0 = 0.5 * (1.0 - alpha);
double a1 = 0.5;
double a2 = 0.5 * alpha;
int n = m_kernel.size();
int halfSize = n / 2;
double subsampleOffset = -0.5;
for (int i = 0; i < n; ++i) {
// Compute the sinc() with offset.
double s = piDouble * (i - halfSize - subsampleOffset);
double sinc = !s ? 1.0 : sin(s) / s;
// Compute Blackman window, matching the offset of the sinc().
double x = (i - subsampleOffset) / n;
double window = a0 - a1 * cos(2.0 * piDouble * x) + a2 * cos(4.0 * piDouble * x);
// Window the sinc() function.
m_kernel[i] = sinc * window;
}
}
void UpSampler::process(const float* sourceP, float* destP, size_t sourceFramesToProcess)
{
bool isInputBlockSizeGood = sourceFramesToProcess == m_inputBlockSize;
ASSERT(isInputBlockSizeGood);
if (!isInputBlockSizeGood)
return;
bool isTempBufferGood = sourceFramesToProcess == m_tempBuffer.size();
ASSERT(isTempBufferGood);
if (!isTempBufferGood)
return;
bool isKernelGood = m_kernel.size() == DefaultKernelSize;
ASSERT(isKernelGood);
if (!isKernelGood)
return;
size_t halfSize = m_kernel.size() / 2;
// Copy source samples to 2nd half of input buffer.
bool isInputBufferGood = m_inputBuffer.size() == sourceFramesToProcess * 2 && halfSize <= sourceFramesToProcess;
ASSERT(isInputBufferGood);
if (!isInputBufferGood)
return;
float* inputP = m_inputBuffer.data() + sourceFramesToProcess;
memcpy(inputP, sourceP, sizeof(float) * sourceFramesToProcess);
// Copy even sample-frames 0,2,4,6... (delayed by the linear phase delay) directly into destP.
for (unsigned i = 0; i < sourceFramesToProcess; ++i)
destP[i * 2] = *((inputP - halfSize) + i);
// Compute odd sample-frames 1,3,5,7...
float* oddSamplesP = m_tempBuffer.data();
m_convolver.process(&m_kernel, sourceP, oddSamplesP, sourceFramesToProcess);
for (unsigned i = 0; i < sourceFramesToProcess; ++i)
destP[i * 2 + 1] = oddSamplesP[i];
// Copy 2nd half of input buffer to 1st half.
memcpy(m_inputBuffer.data(), inputP, sizeof(float) * sourceFramesToProcess);
}
void UpSampler::reset()
{
m_convolver.reset();
m_inputBuffer.zero();
}
size_t UpSampler::latencyFrames() const
{
// Divide by two since this is a linear phase kernel and the delay is at the center of the kernel.
return m_kernel.size() / 2;
}
} // namespace WebCore
#endif // ENABLE(WEB_AUDIO)
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