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/*
* Copyright 2016 The Chromium Authors. All rights reserved.
* Copyright (C) 2020, Apple 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 "config.h"
#if ENABLE(WEB_AUDIO)
#include "IIRProcessor.h"
#include "IIRDSPKernel.h"
namespace WebCore {
IIRProcessor::IIRProcessor(float sampleRate, unsigned numberOfChannels, const Vector<double>& feedforward, const Vector<double>& feedback, bool isFilterStable)
: AudioDSPKernelProcessor(sampleRate, numberOfChannels)
, m_feedforward(feedforward)
, m_feedback(feedback)
, m_isFilterStable(isFilterStable)
{
unsigned feedbackLength = feedback.size();
unsigned feedforwardLength = feedforward.size();
ASSERT(feedbackLength > 0);
ASSERT(feedforwardLength > 0);
// Need to scale the feedback and feedforward coefficients appropriately.
// (It's up to the caller to ensure feedbackCoef[0] is not 0.)
ASSERT(!!feedback[0]);
if (feedback[0] != 1) {
// The provided filter is:
//
// a[0]*y(n) + a[1]*y(n-1) + ... = b[0]*x(n) + b[1]*x(n-1) + ...
//
// We want the leading coefficient of y(n) to be 1:
//
// y(n) + a[1]/a[0]*y(n-1) + ... = b[0]/a[0]*x(n) + b[1]/a[0]*x(n-1) + ...
//
// Thus, the feedback and feedforward coefficients need to be scaled by 1/a[0].
float scale = feedback[0];
for (unsigned k = 1; k < feedbackLength; ++k)
m_feedback[k] /= scale;
for (unsigned k = 0; k < feedforwardLength; ++k)
m_feedforward[k] /= scale;
// The IIRFilter checks to make sure this coefficient is 1, so make it so.
m_feedback[0] = 1;
}
m_responseKernel = makeUnique<IIRDSPKernel>(*this);
}
IIRProcessor::~IIRProcessor()
{
if (isInitialized())
uninitialize();
}
std::unique_ptr<AudioDSPKernel> IIRProcessor::createKernel()
{
return makeUnique<IIRDSPKernel>(*this);
}
void IIRProcessor::process(const AudioBus* source, AudioBus* destination, size_t framesToProcess)
{
if (!isInitialized()) {
destination->zero();
return;
}
// For each channel of our input, process using the corresponding IIRDSPKernel
// into the output channel.
for (size_t i = 0; i < m_kernels.size(); ++i)
m_kernels[i]->process(source->channel(i)->data(), destination->channel(i)->mutableData(), framesToProcess);
}
void IIRProcessor::getFrequencyResponse(unsigned length, const float* frequencyHz, float* magResponse, float* phaseResponse)
{
m_responseKernel->getFrequencyResponse(length, frequencyHz, magResponse, phaseResponse);
}
} // namespace WebCore
#endif // ENABLE(WEB_AUDIO)
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