biquad.h

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/*
 * @file biquad.h
 *
 * @date Sep 10, 2016
 * @author Andrey Belomutskiy, (c) 2012-2020
 */
 
#pragma once
 
class Biquad {
public:
    Biquad();
 
    float filter(float input);
    void reset();
    void cookSteadyState(float steadyStateInput);
 
    void configureBandpass(float samplingFrequency, float centerFrequency, float Q);
 
    // Default Q = 0.54, which is the maximum quality factor without time domain overshoot
    // note that it is less than the maximally flat (frequency domain) Q=0.707, which gives some overshoot
    void configureLowpass(float samplingFrequency, float cutoffFrequency, float Q = 0.54f);
    void configureHighpass(float samplingFrequency, float cutoffFrequency, float Q = 0.54f);
 
private:
    float a0, a1, a2, b1, b2;
    float z1, z2;
};