133 lines
4.5 KiB
C++
133 lines
4.5 KiB
C++
/*
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* Copyright (C) 2013 Google Inc. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of Apple Inc. ("Apple") nor the names of
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* its contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
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* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "config.h"
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#if ENABLE(WEB_AUDIO)
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#include "UpSampler.h"
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#include <wtf/MathExtras.h>
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namespace WebCore {
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UpSampler::UpSampler(size_t inputBlockSize)
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: m_inputBlockSize(inputBlockSize)
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, m_kernel(DefaultKernelSize)
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, m_convolver(inputBlockSize)
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, m_tempBuffer(inputBlockSize)
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, m_inputBuffer(inputBlockSize * 2)
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{
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initializeKernel();
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}
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void UpSampler::initializeKernel()
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{
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// Blackman window parameters.
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double alpha = 0.16;
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double a0 = 0.5 * (1.0 - alpha);
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double a1 = 0.5;
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double a2 = 0.5 * alpha;
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int n = m_kernel.size();
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int halfSize = n / 2;
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double subsampleOffset = -0.5;
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for (int i = 0; i < n; ++i) {
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// Compute the sinc() with offset.
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double s = piDouble * (i - halfSize - subsampleOffset);
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double sinc = !s ? 1.0 : sin(s) / s;
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// Compute Blackman window, matching the offset of the sinc().
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double x = (i - subsampleOffset) / n;
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double window = a0 - a1 * cos(2.0 * piDouble * x) + a2 * cos(4.0 * piDouble * x);
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// Window the sinc() function.
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m_kernel[i] = sinc * window;
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}
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}
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void UpSampler::process(const float* sourceP, float* destP, size_t sourceFramesToProcess)
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{
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bool isInputBlockSizeGood = sourceFramesToProcess == m_inputBlockSize;
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ASSERT(isInputBlockSizeGood);
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if (!isInputBlockSizeGood)
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return;
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bool isTempBufferGood = sourceFramesToProcess == m_tempBuffer.size();
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ASSERT(isTempBufferGood);
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if (!isTempBufferGood)
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return;
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bool isKernelGood = m_kernel.size() == DefaultKernelSize;
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ASSERT(isKernelGood);
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if (!isKernelGood)
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return;
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size_t halfSize = m_kernel.size() / 2;
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// Copy source samples to 2nd half of input buffer.
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bool isInputBufferGood = m_inputBuffer.size() == sourceFramesToProcess * 2 && halfSize <= sourceFramesToProcess;
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ASSERT(isInputBufferGood);
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if (!isInputBufferGood)
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return;
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float* inputP = m_inputBuffer.data() + sourceFramesToProcess;
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memcpy(inputP, sourceP, sizeof(float) * sourceFramesToProcess);
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// Copy even sample-frames 0,2,4,6... (delayed by the linear phase delay) directly into destP.
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for (unsigned i = 0; i < sourceFramesToProcess; ++i)
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destP[i * 2] = *((inputP - halfSize) + i);
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// Compute odd sample-frames 1,3,5,7...
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float* oddSamplesP = m_tempBuffer.data();
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m_convolver.process(&m_kernel, sourceP, oddSamplesP, sourceFramesToProcess);
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for (unsigned i = 0; i < sourceFramesToProcess; ++i)
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destP[i * 2 + 1] = oddSamplesP[i];
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// Copy 2nd half of input buffer to 1st half.
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memcpy(m_inputBuffer.data(), inputP, sizeof(float) * sourceFramesToProcess);
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}
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void UpSampler::reset()
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{
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m_convolver.reset();
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m_inputBuffer.zero();
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}
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size_t UpSampler::latencyFrames() const
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{
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// Divide by two since this is a linear phase kernel and the delay is at the center of the kernel.
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return m_kernel.size() / 2;
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}
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} // namespace WebCore
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#endif // ENABLE(WEB_AUDIO)
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