Source/modules/webaudio/BiquadDSPKernel.h

/*
 * 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
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 *    notice, this list of conditions and the following disclaimer.
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 *    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
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#ifndef BiquadDSPKernel_h
#define BiquadDSPKernel_h

#include "platform/audio/AudioDSPKernel.h"
#include "platform/audio/Biquad.h"
#include "modules/webaudio/BiquadProcessor.h"

namespace blink {

class BiquadProcessor;

// BiquadDSPKernel is an AudioDSPKernel and is responsible for filtering one channel of a BiquadProcessor using a Biquad object.

class BiquadDSPKernel final : public AudioDSPKernel {
public:
    explicit BiquadDSPKernel(BiquadProcessor* processor)
    : AudioDSPKernel(processor)
    {
    }

    // AudioDSPKernel
    virtual void process(const float* source, float* dest, size_t framesToProcess) override;
    virtual void reset() override { m_biquad.reset(); }

    // Get the magnitude and phase response of the filter at the given
    // set of frequencies (in Hz). The phase response is in radians.
    void getFrequencyResponse(int nFrequencies,
                              const float* frequencyHz,
                              float* magResponse,
                              float* phaseResponse);

    virtual double tailTime() const override;
    virtual double latencyTime() const override;

protected:
    Biquad m_biquad;
    BiquadProcessor* biquadProcessor() { return static_cast<BiquadProcessor*>(processor()); }

    // To prevent audio glitches when parameters are changed,
    // dezippering is used to slowly change the parameters.
    void updateCoefficientsIfNecessary();
    // Update the biquad cofficients with the given parameters
    void updateCoefficients(double frequency, double Q, double gain, double detune);

private:
    // Synchronize process() with getting and setting the filter coefficients.
    mutable Mutex m_processLock;
};

} // namespace blink

#endif // BiquadDSPKernel_h