Rack/plugins/community/repos/Autodafe/src/Biquad.cpp

//
//  Biquad.cpp
//
//  Created by Nigel Redmon on 11/24/12
//  EarLevel Engineering: earlevel.com
//  Copyright 2012 Nigel Redmon
//
//  For a complete explanation of the Biquad code:
//  http://www.earlevel.com/main/2012/11/26/biquad-c-source-code/
//
//  License:
//
//  This source code is provided as is, without warranty.
//  You may copy and distribute verbatim copies of this document.
//  You may modify and use this source code to create binary code
//  for your own purposes, free or commercial.
//

#include <math.h>
#include "Biquad.h"

namespace rack_plugin_Autodafe {

Biquad::Biquad() {
	type = bq_type_lowpass;
	a0 = 1.0;
	a1 = a2 = b1 = b2 = 0.0;
	Fc = 0.50;
	Q = 0.707;
	peakGain = 0.0;
	z1 = z2 = 0.0;
}

Biquad::Biquad(int type, double Fc, double Q, double peakGainDB) {
	setBiquad(type, Fc, Q, peakGainDB);
	z1 = z2 = 0.0;
}

Biquad::~Biquad() {
}

void Biquad::setType(int type) {
	this->type = type;
	calcBiquad();
}

void Biquad::setQ(double Q) {
	this->Q = Q;
	calcBiquad();
}

void Biquad::setFc(double Fc) {
	this->Fc = Fc;
	calcBiquad();
}

void Biquad::setPeakGain(double peakGainDB) {
	this->peakGain = peakGainDB;
	calcBiquad();
}

void Biquad::setBiquad(int type, double Fc, double Q, double peakGainDB) {
	this->type = type;
	this->Q = Q;
	this->Fc = Fc;
	setPeakGain(peakGainDB);
}

void Biquad::calcBiquad(void) {
	double norm;
	double V = pow(10, fabs(peakGain) / 20.0);
	double K = tan(M_PI * Fc);
	switch (this->type) {
	case bq_type_lowpass:
		norm = 1 / (1 + K / Q + K * K);
		a0 = K * K * norm;
		a1 = 2 * a0;
		a2 = a0;
		b1 = 2 * (K * K - 1) * norm;
		b2 = (1 - K / Q + K * K) * norm;
		break;

	case bq_type_highpass:
		norm = 1 / (1 + K / Q + K * K);
		a0 = 1 * norm;
		a1 = -2 * a0;
		a2 = a0;
		b1 = 2 * (K * K - 1) * norm;
		b2 = (1 - K / Q + K * K) * norm;
		break;

	case bq_type_bandpass:
		norm = 1 / (1 + K / Q + K * K);
		a0 = K / Q * norm;
		a1 = 0;
		a2 = -a0;
		b1 = 2 * (K * K - 1) * norm;
		b2 = (1 - K / Q + K * K) * norm;
		break;

	case bq_type_notch:
		norm = 1 / (1 + K / Q + K * K);
		a0 = (1 + K * K) * norm;
		a1 = 2 * (K * K - 1) * norm;
		a2 = a0;
		b1 = a1;
		b2 = (1 - K / Q + K * K) * norm;
		break;

	case bq_type_peak:
		if (peakGain >= 0) {    // boost
			norm = 1 / (1 + 1 / Q * K + K * K);
			a0 = (1 + V / Q * K + K * K) * norm;
			a1 = 2 * (K * K - 1) * norm;
			a2 = (1 - V / Q * K + K * K) * norm;
			b1 = a1;
			b2 = (1 - 1 / Q * K + K * K) * norm;
		}
		else {    // cut
			norm = 1 / (1 + V / Q * K + K * K);
			a0 = (1 + 1 / Q * K + K * K) * norm;
			a1 = 2 * (K * K - 1) * norm;
			a2 = (1 - 1 / Q * K + K * K) * norm;
			b1 = a1;
			b2 = (1 - V / Q * K + K * K) * norm;
		}
		break;
	case bq_type_lowshelf:
		if (peakGain >= 0) {    // boost
			norm = 1 / (1 + sqrt(2) * K + K * K);
			a0 = (1 + sqrt(2 * V) * K + V * K * K) * norm;
			a1 = 2 * (V * K * K - 1) * norm;
			a2 = (1 - sqrt(2 * V) * K + V * K * K) * norm;
			b1 = 2 * (K * K - 1) * norm;
			b2 = (1 - sqrt(2) * K + K * K) * norm;
		}
		else {    // cut
			norm = 1 / (1 + sqrt(2 * V) * K + V * K * K);
			a0 = (1 + sqrt(2) * K + K * K) * norm;
			a1 = 2 * (K * K - 1) * norm;
			a2 = (1 - sqrt(2) * K + K * K) * norm;
			b1 = 2 * (V * K * K - 1) * norm;
			b2 = (1 - sqrt(2 * V) * K + V * K * K) * norm;
		}
		break;
	case bq_type_highshelf:
		if (peakGain >= 0) {    // boost
			norm = 1 / (1 + sqrt(2) * K + K * K);
			a0 = (V + sqrt(2 * V) * K + K * K) * norm;
			a1 = 2 * (K * K - V) * norm;
			a2 = (V - sqrt(2 * V) * K + K * K) * norm;
			b1 = 2 * (K * K - 1) * norm;
			b2 = (1 - sqrt(2) * K + K * K) * norm;
		}
		else {    // cut
			norm = 1 / (V + sqrt(2 * V) * K + K * K);
			a0 = (1 + sqrt(2) * K + K * K) * norm;
			a1 = 2 * (K * K - 1) * norm;
			a2 = (1 - sqrt(2) * K + K * K) * norm;
			b1 = 2 * (K * K - V) * norm;
			b2 = (V - sqrt(2 * V) * K + K * K) * norm;
		}
		break;
	}

	return;
}

} // namespace rack_plugin_Autodafe