[webkit-reviews] review granted: [Bug 34907] audio engine: add FFTConvolver class : [Attachment 65611] Patch

[bugzilla-daemon at webkit.org]

Kenneth Russell <kbr at google.com> has granted Chris Rogers
<crogers at google.com>'s request for review:
Bug 34907: audio engine: add FFTConvolver class
https://bugs.webkit.org/show_bug.cgi?id=34907

Attachment 65611: Patch
https://bugs.webkit.org/attachment.cgi?id=65611&action=review

------- Additional Comments from Kenneth Russell <kbr at google.com>
I'm r+'ing this based on earlier review but want to highlight a couple of
portability issues.

> Index: WebCore/platform/audio/FFTConvolver.cpp
> ===================================================================
> --- WebCore/platform/audio/FFTConvolver.cpp	(revision 0)
> +++ WebCore/platform/audio/FFTConvolver.cpp	(revision 0)
> @@ -0,0 +1,108 @@
> +/*
> + * 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 "config.h"
> +
> +#if ENABLE(WEB_AUDIO)
> +
> +#include "FFTConvolver.h"
> +
> +#include "Accelerate.h"

This #include should be surrounded by some PLATFORM or OS macro for Mac OS X,
and a compile-time or run-time failure on other platforms.

> +
> +namespace WebCore {
> +
> +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, float* sourceP, float*
destP, size_t framesToProcess)
> +{
> +    // FIXME: make so framesToProcess is not required to fit evenly into
fftSize/2
> +
> +    // Copy samples to input buffer (note contraint above!)
> +    float* inputP = m_inputBuffer.data();
> +
> +    // Sanity check
> +    bool isCopyGood1 = sourceP && inputP && m_readWriteIndex +
framesToProcess <= m_inputBuffer.size();
> +    ASSERT(isCopyGood1);
> +    if (!isCopyGood1)
> +	   return;
> +    
> +    memcpy(inputP + m_readWriteIndex, sourceP, sizeof(float) *
framesToProcess);
> +
> +    // Copy samples from output buffer
> +    float* outputP = m_outputBuffer.data();
> +
> +    // Sanity check
> +    bool isCopyGood2 = destP && outputP && m_readWriteIndex +
framesToProcess <= m_outputBuffer.size();
> +    ASSERT(isCopyGood2);
> +    if (!isCopyGood2)
> +	   return;
> +
> +    memcpy(destP, outputP + m_readWriteIndex, sizeof(float) *
framesToProcess);
> +    m_readWriteIndex += framesToProcess;
> +
> +
> +    // Check if it's time to perform the next FFT
> +    size_t halfSize = fftSize() / 2;
> +    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);

This should be similarly covered by a Mac-specific PLATFORM or OS macro.

> +
> +	   // 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 WebCore
> +
> +#endif // ENABLE(WEB_AUDIO)