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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:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * 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.
* * Neither the name of Google Inc. 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 THE COPYRIGHT HOLDERS AND 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 THE COPYRIGHT
* OWNER OR 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 "platform/audio/UpSampler.h"
#include "wtf/MathExtras.h"
namespace blink {
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(twoPiDouble * x) + a2 * cos(twoPiDouble * 2.0 * 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 blink
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