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// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "modules/webaudio/IIRDSPKernel.h"
#include "platform/FloatConversion.h"
namespace blink {
void IIRDSPKernel::process(const float* source, float* destination, size_t framesToProcess)
{
ASSERT(source);
ASSERT(destination);
m_iir.process(source, destination, framesToProcess);
}
void IIRDSPKernel::getFrequencyResponse(int nFrequencies, const float* frequencyHz, float* magResponse, float* phaseResponse)
{
bool isGood = nFrequencies > 0 && frequencyHz && magResponse && phaseResponse;
ASSERT(isGood);
if (!isGood)
return;
Vector<float> frequency(nFrequencies);
double nyquist = this->nyquist();
// Convert from frequency in Hz to normalized frequency (0 -> 1),
// with 1 equal to the Nyquist frequency.
for (int k = 0; k < nFrequencies; ++k)
frequency[k] = narrowPrecisionToFloat(frequencyHz[k] / nyquist);
m_iir.getFrequencyResponse(nFrequencies, frequency.data(), magResponse, phaseResponse);
}
double IIRDSPKernel::tailTime() const
{
// TODO(rtoy): This is true mathematically (infinite impulse response), but perhaps it should be
// limited to a smaller value, possibly based on the actual filter coefficients. To do that, we
// would probably need to find the pole, r, with largest magnitude and select some threshold,
// eps, such that |r|^n < eps for all n >= N. N is then the tailTime for the filter. If the
// the magnitude of r is greater than or equal to 1, the infinity is the right answer. (There is
// no constraint on the IIR filter that it be stable.)
return std::numeric_limits<double>::infinity();
}
double IIRDSPKernel::latencyTime() const
{
return 0;
}
} // namespace blink
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