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

/*
 * Copyright (C) 2011, 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.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. 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 INC. 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 "modules/webaudio/WaveShaperDSPKernel.h"
#include "wtf/PtrUtil.h"
#include "wtf/Threading.h"
#include <algorithm>

const unsigned RenderingQuantum = 128;

namespace blink {

WaveShaperDSPKernel::WaveShaperDSPKernel(WaveShaperProcessor* processor)
    : AudioDSPKernel(processor) {
  if (processor->oversample() != WaveShaperProcessor::OverSampleNone)
    lazyInitializeOversampling();
}

void WaveShaperDSPKernel::lazyInitializeOversampling() {
  if (!m_tempBuffer) {
    m_tempBuffer = wrapUnique(new AudioFloatArray(RenderingQuantum * 2));
    m_tempBuffer2 = wrapUnique(new AudioFloatArray(RenderingQuantum * 4));
    m_upSampler = wrapUnique(new UpSampler(RenderingQuantum));
    m_downSampler = wrapUnique(new DownSampler(RenderingQuantum * 2));
    m_upSampler2 = wrapUnique(new UpSampler(RenderingQuantum * 2));
    m_downSampler2 = wrapUnique(new DownSampler(RenderingQuantum * 4));
  }
}

void WaveShaperDSPKernel::process(const float* source,
                                  float* destination,
                                  size_t framesToProcess) {
  switch (getWaveShaperProcessor()->oversample()) {
    case WaveShaperProcessor::OverSampleNone:
      processCurve(source, destination, framesToProcess);
      break;
    case WaveShaperProcessor::OverSample2x:
      processCurve2x(source, destination, framesToProcess);
      break;
    case WaveShaperProcessor::OverSample4x:
      processCurve4x(source, destination, framesToProcess);
      break;

    default:
      ASSERT_NOT_REACHED();
  }
}

void WaveShaperDSPKernel::processCurve(const float* source,
                                       float* destination,
                                       size_t framesToProcess) {
  DCHECK(source);
  DCHECK(destination);
  DCHECK(getWaveShaperProcessor());

  Vector<float>* curve = getWaveShaperProcessor()->curve();
  if (!curve) {
    // Act as "straight wire" pass-through if no curve is set.
    memcpy(destination, source, sizeof(float) * framesToProcess);
    return;
  }

  float* curveData = curve->data();
  int curveLength = curve->size();

  DCHECK(curveData);

  if (!curveData || !curveLength) {
    memcpy(destination, source, sizeof(float) * framesToProcess);
    return;
  }

  // Apply waveshaping curve.
  for (unsigned i = 0; i < framesToProcess; ++i) {
    const float input = source[i];

    // Calculate a virtual index based on input -1 -> +1 with -1 being curve[0],
    // +1 being curve[curveLength - 1], and 0 being at the center of the curve
    // data. Then linearly interpolate between the two points in the curve.
    double virtualIndex = 0.5 * (input + 1) * (curveLength - 1);
    double output;

    if (virtualIndex < 0) {
      // input < -1, so use curve[0]
      output = curveData[0];
    } else if (virtualIndex >= curveLength - 1) {
      // input >= 1, so use last curve value
      output = curveData[curveLength - 1];
    } else {
      // The general case where -1 <= input < 1, where 0 <= virtualIndex <
      // curveLength - 1, so interpolate between the nearest samples on the
      // curve.
      unsigned index1 = static_cast<unsigned>(virtualIndex);
      unsigned index2 = index1 + 1;
      double interpolationFactor = virtualIndex - index1;

      double value1 = curveData[index1];
      double value2 = curveData[index2];

      output =
          (1.0 - interpolationFactor) * value1 + interpolationFactor * value2;
    }
    destination[i] = output;
  }
}

void WaveShaperDSPKernel::processCurve2x(const float* source,
                                         float* destination,
                                         size_t framesToProcess) {
  bool isSafe = framesToProcess == RenderingQuantum;
  DCHECK(isSafe);
  if (!isSafe)
    return;

  float* tempP = m_tempBuffer->data();

  m_upSampler->process(source, tempP, framesToProcess);

  // Process at 2x up-sampled rate.
  processCurve(tempP, tempP, framesToProcess * 2);

  m_downSampler->process(tempP, destination, framesToProcess * 2);
}

void WaveShaperDSPKernel::processCurve4x(const float* source,
                                         float* destination,
                                         size_t framesToProcess) {
  bool isSafe = framesToProcess == RenderingQuantum;
  DCHECK(isSafe);
  if (!isSafe)
    return;

  float* tempP = m_tempBuffer->data();
  float* tempP2 = m_tempBuffer2->data();

  m_upSampler->process(source, tempP, framesToProcess);
  m_upSampler2->process(tempP, tempP2, framesToProcess * 2);

  // Process at 4x up-sampled rate.
  processCurve(tempP2, tempP2, framesToProcess * 4);

  m_downSampler2->process(tempP2, tempP, framesToProcess * 4);
  m_downSampler->process(tempP, destination, framesToProcess * 2);
}

void WaveShaperDSPKernel::reset() {
  if (m_upSampler) {
    m_upSampler->reset();
    m_downSampler->reset();
    m_upSampler2->reset();
    m_downSampler2->reset();
  }
}

double WaveShaperDSPKernel::latencyTime() const {
  size_t latencyFrames = 0;
  WaveShaperDSPKernel* kernel = const_cast<WaveShaperDSPKernel*>(this);

  switch (kernel->getWaveShaperProcessor()->oversample()) {
    case WaveShaperProcessor::OverSampleNone:
      break;
    case WaveShaperProcessor::OverSample2x:
      latencyFrames += m_upSampler->latencyFrames();
      latencyFrames += m_downSampler->latencyFrames();
      break;
    case WaveShaperProcessor::OverSample4x: {
      // Account for first stage upsampling.
      latencyFrames += m_upSampler->latencyFrames();
      latencyFrames += m_downSampler->latencyFrames();

      // Account for second stage upsampling.
      // and divide by 2 to get back down to the regular sample-rate.
      size_t latencyFrames2 =
          (m_upSampler2->latencyFrames() + m_downSampler2->latencyFrames()) / 2;
      latencyFrames += latencyFrames2;
      break;
    }
    default:
      ASSERT_NOT_REACHED();
  }

  return static_cast<double>(latencyFrames) / sampleRate();
}

}  // namespace blink