third_party/WebKit/Source/platform/audio/FFTConvolver.cpp

/*
 * Copyright (C) 2010 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.
 * 3.  Neither the name of Apple Computer, Inc. ("Apple") 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 APPLE 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 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 "platform/audio/FFTConvolver.h"
#include "platform/audio/VectorMath.h"

namespace blink {

using namespace VectorMath;

FFTConvolver::FFTConvolver(size_t fftSize)
    : m_frame(fftSize),
      m_readWriteIndex(0),
      m_inputBuffer(fftSize)  // 2nd half of buffer is always zeroed
      ,
      m_outputBuffer(fftSize),
      m_lastOverlapBuffer(fftSize / 2) {}

void FFTConvolver::process(FFTFrame* fftKernel,
                           const float* sourceP,
                           float* destP,
                           size_t framesToProcess) {
  size_t halfSize = fftSize() / 2;

  // framesToProcess must be an exact multiple of halfSize,
  // or halfSize is a multiple of framesToProcess when halfSize >
  // framesToProcess.
  bool isGood = !(halfSize % framesToProcess && framesToProcess % halfSize);
  ASSERT(isGood);
  if (!isGood)
    return;

  size_t numberOfDivisions =
      halfSize <= framesToProcess ? (framesToProcess / halfSize) : 1;
  size_t divisionSize = numberOfDivisions == 1 ? framesToProcess : halfSize;

  for (size_t i = 0; i < numberOfDivisions;
       ++i, sourceP += divisionSize, destP += divisionSize) {
    // Copy samples to input buffer (note contraint above!)
    float* inputP = m_inputBuffer.data();

    // Sanity check
    bool isCopyGood1 = sourceP && inputP &&
                       m_readWriteIndex + divisionSize <= m_inputBuffer.size();
    ASSERT(isCopyGood1);
    if (!isCopyGood1)
      return;

    memcpy(inputP + m_readWriteIndex, sourceP, sizeof(float) * divisionSize);

    // Copy samples from output buffer
    float* outputP = m_outputBuffer.data();

    // Sanity check
    bool isCopyGood2 = destP && outputP &&
                       m_readWriteIndex + divisionSize <= m_outputBuffer.size();
    ASSERT(isCopyGood2);
    if (!isCopyGood2)
      return;

    memcpy(destP, outputP + m_readWriteIndex, sizeof(float) * divisionSize);
    m_readWriteIndex += divisionSize;

    // Check if it's time to perform the next FFT
    if (m_readWriteIndex == halfSize) {
      // The input buffer is now filled (get frequency-domain version)
      m_frame.doFFT(m_inputBuffer.data());
      m_frame.multiply(*fftKernel);
      m_frame.doInverseFFT(m_outputBuffer.data());

      // Overlap-add 1st half from previous time
      vadd(m_outputBuffer.data(), 1, m_lastOverlapBuffer.data(), 1,
           m_outputBuffer.data(), 1, halfSize);

      // Finally, save 2nd half of result
      bool isCopyGood3 = m_outputBuffer.size() == 2 * halfSize &&
                         m_lastOverlapBuffer.size() == halfSize;
      ASSERT(isCopyGood3);
      if (!isCopyGood3)
        return;

      memcpy(m_lastOverlapBuffer.data(), m_outputBuffer.data() + halfSize,
             sizeof(float) * halfSize);

      // Reset index back to start for next time
      m_readWriteIndex = 0;
    }
  }
}

void FFTConvolver::reset() {
  m_lastOverlapBuffer.zero();
  m_readWriteIndex = 0;
}

}  // namespace blink