src/third_party/WebKit/Source/modules/webaudio/WaveShaperDSPKernel.cpp

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  10  *    notice, this list of conditions and the following disclaimer in the
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  13  * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND ANY
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  15  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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  24
  25 #include "config.h"
  26
  27 #if ENABLE(WEB_AUDIO)
  28
  29 #include "modules/webaudio/WaveShaperDSPKernel.h"
  30
  31 #include "wtf/MainThread.h"
  32 #include "wtf/Threading.h"
  33 #include <algorithm>
  34
  35 const unsigned RenderingQuantum = 128;
  36
  37 namespace blink {
  38
  39 WaveShaperDSPKernel::WaveShaperDSPKernel(WaveShaperProcessor* processor)
  40     : AudioDSPKernel(processor)
  41 {
  42     if (processor->oversample() != WaveShaperProcessor::OverSampleNone)
  43         lazyInitializeOversampling();
  44 }
  45
  46 void WaveShaperDSPKernel::lazyInitializeOversampling()
  47 {
  48     if (!m_tempBuffer) {
  49         m_tempBuffer = adoptPtr(new AudioFloatArray(RenderingQuantum * 2));
  50         m_tempBuffer2 = adoptPtr(new AudioFloatArray(RenderingQuantum * 4));
  51         m_upSampler = adoptPtr(new UpSampler(RenderingQuantum));
  52         m_downSampler = adoptPtr(new DownSampler(RenderingQuantum * 2));
  53         m_upSampler2 = adoptPtr(new UpSampler(RenderingQuantum * 2));
  54         m_downSampler2 = adoptPtr(new DownSampler(RenderingQuantum * 4));
  55     }
  56 }
  57
  58 void WaveShaperDSPKernel::process(const float* source, float* destination, size_t framesToProcess)
  59 {
  60     switch (waveShaperProcessor()->oversample()) {
  61     case WaveShaperProcessor::OverSampleNone:
  62         processCurve(source, destination, framesToProcess);
  63         break;
  64     case WaveShaperProcessor::OverSample2x:
  65         processCurve2x(source, destination, framesToProcess);
  66         break;
  67     case WaveShaperProcessor::OverSample4x:
  68         processCurve4x(source, destination, framesToProcess);
  69         break;
  70
  71     default:
  72         ASSERT_NOT_REACHED();
  73     }
  74 }
  75
  76 void WaveShaperDSPKernel::processCurve(const float* source, float* destination, size_t framesToProcess)
  77 {
  78     ASSERT(source && destination && waveShaperProcessor());
  79
  80     DOMFloat32Array* curve = waveShaperProcessor()->curve();
  81     if (!curve) {
  82         // Act as "straight wire" pass-through if no curve is set.
  83         memcpy(destination, source, sizeof(float) * framesToProcess);
  84         return;
  85     }
  86
  87     float* curveData = curve->data();
  88     int curveLength = curve->length();
  89
  90     ASSERT(curveData);
  91
  92     if (!curveData || !curveLength) {
  93         memcpy(destination, source, sizeof(float) * framesToProcess);
  94         return;
  95     }
  96
  97     // Apply waveshaping curve.
  98     for (unsigned i = 0; i < framesToProcess; ++i) {
  99         const float input = source[i];
 100
 101         // Calculate a virtual index based on input -1 -> +1 with -1 being curve[0], +1 being
 102         // curve[curveLength - 1], and 0 being at the center of the curve data. Then linearly
 103         // interpolate between the two points in the curve.
 104         double virtualIndex = 0.5 * (input + 1) * (curveLength - 1);
 105         double output;
 106
 107         if (virtualIndex < 0) {
 108             // input < -1, so use curve[0]
 109             output = curveData[0];
 110         } else if (virtualIndex >= curveLength - 1) {
 111             // input >= 1, so use last curve value
 112             output = curveData[curveLength - 1];
 113         } else {
 114             // The general case where -1 <= input < 1, where 0 <= virtualIndex < curveLength - 1,
 115             // so interpolate between the nearest samples on the curve.
 116             unsigned index1 = static_cast<unsigned>(virtualIndex);
 117             unsigned index2 = index1 + 1;
 118             double interpolationFactor = virtualIndex - index1;
 119
 120             double value1 = curveData[index1];
 121             double value2 = curveData[index2];
 122
 123             output = (1.0 - interpolationFactor) * value1 + interpolationFactor * value2;
 124         }
 125         destination[i] = output;
 126     }
 127 }
 128
 129 void WaveShaperDSPKernel::processCurve2x(const float* source, float* destination, size_t framesToProcess)
 130 {
 131     bool isSafe = framesToProcess == RenderingQuantum;
 132     ASSERT(isSafe);
 133     if (!isSafe)
 134         return;
 135
 136     float* tempP = m_tempBuffer->data();
 137
 138     m_upSampler->process(source, tempP, framesToProcess);
 139
 140     // Process at 2x up-sampled rate.
 141     processCurve(tempP, tempP, framesToProcess * 2);
 142
 143     m_downSampler->process(tempP, destination, framesToProcess * 2);
 144 }
 145
 146 void WaveShaperDSPKernel::processCurve4x(const float* source, float* destination, size_t framesToProcess)
 147 {
 148     bool isSafe = framesToProcess == RenderingQuantum;
 149     ASSERT(isSafe);
 150     if (!isSafe)
 151         return;
 152
 153     float* tempP = m_tempBuffer->data();
 154     float* tempP2 = m_tempBuffer2->data();
 155
 156     m_upSampler->process(source, tempP, framesToProcess);
 157     m_upSampler2->process(tempP, tempP2, framesToProcess * 2);
 158
 159     // Process at 4x up-sampled rate.
 160     processCurve(tempP2, tempP2, framesToProcess * 4);
 161
 162     m_downSampler2->process(tempP2, tempP, framesToProcess * 4);
 163     m_downSampler->process(tempP, destination, framesToProcess * 2);
 164 }
 165
 166 void WaveShaperDSPKernel::reset()
 167 {
 168     if (m_upSampler) {
 169         m_upSampler->reset();
 170         m_downSampler->reset();
 171         m_upSampler2->reset();
 172         m_downSampler2->reset();
 173     }
 174 }
 175
 176 double WaveShaperDSPKernel::latencyTime() const
 177 {
 178     size_t latencyFrames = 0;
 179     WaveShaperDSPKernel* kernel = const_cast<WaveShaperDSPKernel*>(this);
 180
 181     switch (kernel->waveShaperProcessor()->oversample()) {
 182     case WaveShaperProcessor::OverSampleNone:
 183         break;
 184     case WaveShaperProcessor::OverSample2x:
 185         latencyFrames += m_upSampler->latencyFrames();
 186         latencyFrames += m_downSampler->latencyFrames();
 187         break;
 188     case WaveShaperProcessor::OverSample4x:
 189         {
 190             // Account for first stage upsampling.
 191             latencyFrames += m_upSampler->latencyFrames();
 192             latencyFrames += m_downSampler->latencyFrames();
 193
 194             // Account for second stage upsampling.
 195             // and divide by 2 to get back down to the regular sample-rate.
 196             size_t latencyFrames2 = (m_upSampler2->latencyFrames() + m_downSampler2->latencyFrames()) / 2;
 197             latencyFrames += latencyFrames2;
 198             break;
 199         }
 200     default:
 201         ASSERT_NOT_REACHED();
 202     }
 203
 204     return static_cast<double>(latencyFrames) / sampleRate();
 205 }
 206
 207 } // namespace blink
 208
 209 #endif // ENABLE(WEB_AUDIO)