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| 1 /* |
| 2 * Copyright (C) 2013 Google Inc. All rights reserved. |
| 3 * |
| 4 * Redistribution and use in source and binary forms, with or without |
| 5 * modification, are permitted provided that the following conditions are |
| 6 * met: |
| 7 * |
| 8 * * Redistributions of source code must retain the above copyright |
| 9 * notice, this list of conditions and the following disclaimer. |
| 10 * * Redistributions in binary form must reproduce the above |
| 11 * copyright notice, this list of conditions and the following disclaimer |
| 12 * in the documentation and/or other materials provided with the |
| 13 * distribution. |
| 14 * * Neither the name of Google Inc. nor the names of its |
| 15 * contributors may be used to endorse or promote products derived from |
| 16 * this software without specific prior written permission. |
| 17 * |
| 18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| 19 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| 20 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| 21 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| 22 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| 23 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| 24 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| 25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| 26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| 27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| 28 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| 29 */ |
| 30 |
| 31 #include "config.h" |
| 32 |
| 33 #if ENABLE(WEB_AUDIO) |
| 34 |
| 35 #include "core/platform/audio/UpSampler.h" |
| 36 |
| 37 #include "wtf/MathExtras.h" |
| 38 |
| 39 namespace WebCore { |
| 40 |
| 41 UpSampler::UpSampler(size_t inputBlockSize) |
| 42 : m_inputBlockSize(inputBlockSize) |
| 43 , m_kernel(DefaultKernelSize) |
| 44 , m_tempBuffer(inputBlockSize) |
| 45 , m_inputBuffer(inputBlockSize * 2) |
| 46 , m_convolver(inputBlockSize) |
| 47 { |
| 48 initializeKernel(); |
| 49 } |
| 50 |
| 51 void UpSampler::initializeKernel() |
| 52 { |
| 53 // Blackman window parameters. |
| 54 double alpha = 0.16; |
| 55 double a0 = 0.5 * (1.0 - alpha); |
| 56 double a1 = 0.5; |
| 57 double a2 = 0.5 * alpha; |
| 58 |
| 59 int n = m_kernel.size(); |
| 60 int halfSize = n / 2; |
| 61 double subsampleOffset = -0.5; |
| 62 |
| 63 for (int i = 0; i < n; ++i) { |
| 64 // Compute the sinc() with offset. |
| 65 double s = piDouble * (i - halfSize - subsampleOffset); |
| 66 double sinc = !s ? 1.0 : sin(s) / s; |
| 67 |
| 68 // Compute Blackman window, matching the offset of the sinc(). |
| 69 double x = (i - subsampleOffset) / n; |
| 70 double window = a0 - a1 * cos(2.0 * piDouble * x) + a2 * cos(4.0 * piDou
ble * x); |
| 71 |
| 72 // Window the sinc() function. |
| 73 m_kernel[i] = sinc * window; |
| 74 } |
| 75 } |
| 76 |
| 77 void UpSampler::process(const float* sourceP, float* destP, size_t sourceFramesT
oProcess) |
| 78 { |
| 79 bool isInputBlockSizeGood = sourceFramesToProcess == m_inputBlockSize; |
| 80 ASSERT(isInputBlockSizeGood); |
| 81 if (!isInputBlockSizeGood) |
| 82 return; |
| 83 |
| 84 bool isTempBufferGood = sourceFramesToProcess == m_tempBuffer.size(); |
| 85 ASSERT(isTempBufferGood); |
| 86 if (!isTempBufferGood) |
| 87 return; |
| 88 |
| 89 bool isKernelGood = m_kernel.size() == DefaultKernelSize; |
| 90 ASSERT(isKernelGood); |
| 91 if (!isKernelGood) |
| 92 return; |
| 93 |
| 94 size_t halfSize = m_kernel.size() / 2; |
| 95 |
| 96 // Copy source samples to 2nd half of input buffer. |
| 97 bool isInputBufferGood = m_inputBuffer.size() == sourceFramesToProcess * 2 &
& halfSize <= sourceFramesToProcess; |
| 98 ASSERT(isInputBufferGood); |
| 99 if (!isInputBufferGood) |
| 100 return; |
| 101 |
| 102 float* inputP = m_inputBuffer.data() + sourceFramesToProcess; |
| 103 memcpy(inputP, sourceP, sizeof(float) * sourceFramesToProcess); |
| 104 |
| 105 // Copy even sample-frames 0,2,4,6... (delayed by the linear phase delay) di
rectly into destP. |
| 106 for (unsigned i = 0; i < sourceFramesToProcess; ++i) |
| 107 destP[i * 2] = inputP[i - halfSize]; |
| 108 |
| 109 // Compute odd sample-frames 1,3,5,7... |
| 110 float* oddSamplesP = m_tempBuffer.data(); |
| 111 m_convolver.process(&m_kernel, sourceP, oddSamplesP, sourceFramesToProcess); |
| 112 |
| 113 for (unsigned i = 0; i < sourceFramesToProcess; ++i) |
| 114 destP[i * 2 + 1] = oddSamplesP[i]; |
| 115 |
| 116 // Copy 2nd half of input buffer to 1st half. |
| 117 memcpy(m_inputBuffer.data(), inputP, sizeof(float) * sourceFramesToProcess); |
| 118 } |
| 119 |
| 120 void UpSampler::reset() |
| 121 { |
| 122 m_convolver.reset(); |
| 123 m_inputBuffer.zero(); |
| 124 } |
| 125 |
| 126 size_t UpSampler::latencyFrames() const |
| 127 { |
| 128 // Divide by two since this is a linear phase kernel and the delay is at the
center of the kernel. |
| 129 return m_kernel.size() / 2; |
| 130 } |
| 131 |
| 132 } // namespace WebCore |
| 133 |
| 134 #endif // ENABLE(WEB_AUDIO) |
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