jthedering
d68b958bc8
Fixed: The method BiQuad::gainAt was returning wrong values. As this method was only used for testing purposes, this change is not user-visible.
146 lines
3.6 KiB
C++
146 lines
3.6 KiB
C++
/*
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This file is part of EqualizerAPO, a system-wide equalizer.
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Copyright (C) 2013 Jonas Thedering
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License along
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with this program; if not, write to the Free Software Foundation, Inc.,
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51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#include "BiQuad.h"
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using namespace std;
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BiQuad::BiQuad(Type type, double dbGain, double freq, double srate, double bandwidthOrQOrS, bool isBandwidth)
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{
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double A;
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if(type == PEAKING || type == LOW_SHELF || type == HIGH_SHELF)
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A = pow(10, dbGain / 40);
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else
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A = pow(10, dbGain / 20);
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double omega = 2 * M_PI * freq / srate;
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double sn = sin(omega);
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double cs = cos(omega);
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double alpha;
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double beta = -1;
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if (type == LOW_SHELF || type == HIGH_SHELF) // S
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{
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alpha = sn/2 * sqrt((A + 1/A) * (1/bandwidthOrQOrS - 1) + 2);
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beta = 2 * sqrt(A) * alpha;
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}
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else if(isBandwidth) // BW
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alpha = sn * sinh(M_LN2/2 * bandwidthOrQOrS * omega / sn);
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else // Q
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alpha = sn / (2 * bandwidthOrQOrS);
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double b0, b1, b2, a0, a1, a2;
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switch(type)
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{
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case LOW_PASS:
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b0 = (1 - cs) /2;
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b1 = 1 - cs;
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b2 = (1 - cs) /2;
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a0 = 1 + alpha;
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a1 = -2 * cs;
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a2 = 1 - alpha;
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break;
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case HIGH_PASS:
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b0 = (1 + cs) /2;
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b1 = -(1 + cs);
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b2 = (1 + cs) /2;
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a0 = 1 + alpha;
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a1 = -2 * cs;
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a2 = 1 - alpha;
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break;
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case BAND_PASS:
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b0 = alpha;
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b1 = 0;
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b2 = -alpha;
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a0 = 1 + alpha;
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a1 = -2 * cs;
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a2 = 1 - alpha;
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break;
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case NOTCH:
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b0 = 1;
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b1 = -2 * cs;
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b2 = 1;
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a0 = 1 + alpha;
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a1 = -2 * cs;
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a2 = 1 - alpha;
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break;
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case ALL_PASS:
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b0 = 1 - alpha;
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b1 = -2 * cs;
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b2 = 1 + alpha;
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a0 = 1 + alpha;
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a1 = -2 * cs;
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a2 = 1 - alpha;
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break;
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case PEAKING:
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b0 = 1 + (alpha * A);
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b1 = -2 * cs;
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b2 = 1 - (alpha * A);
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a0 = 1 + (alpha / A);
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a1 = -2 * cs;
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a2 = 1 - (alpha / A);
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break;
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case LOW_SHELF:
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b0 = A * ((A + 1) - (A - 1) * cs + beta);
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b1 = 2 * A * ((A - 1) - (A + 1) * cs);
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b2 = A * ((A + 1) - (A - 1) * cs - beta);
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a0 = (A + 1) + (A - 1) * cs + beta;
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a1 = -2 * ((A - 1) + (A + 1) * cs);
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a2 = (A + 1) + (A - 1) * cs - beta;
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break;
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case HIGH_SHELF:
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b0 = A * ((A + 1) + (A - 1) * cs + beta);
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b1 = -2 * A * ((A - 1) + (A + 1) * cs);
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b2 = A * ((A + 1) + (A - 1) * cs - beta);
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a0 = (A + 1) - (A - 1) * cs + beta;
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a1 = 2 * ((A - 1) - (A + 1) * cs);
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a2 = (A + 1) - (A - 1) * cs - beta;
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break;
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}
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this->a0 = b0 / a0;
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this->a[0] = b1 / a0;
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this->a[1] = b2 / a0;
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this->a[2] = a1 / a0;
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this->a[3] = a2 / a0;
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x1 = 0;
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x2 = 0;
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y1 = 0;
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y2 = 0;
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}
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double BiQuad::gainAt(double freq, double srate)
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{
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double omega = 2 * M_PI * freq / srate;
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double sn = sin(omega/2.0);
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double phi = sn * sn;
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double b0 = this->a0;
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double b1 = this->a[0];
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double b2 = this->a[1];
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double a0 = 1.0;
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double a1 = this->a[2];
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double a2 = this->a[3];
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double dbGain = 10*log10( pow(b0+b1+b2, 2) - 4*(b0*b1 + 4*b0*b2 + b1*b2)*phi + 16*b0*b2*phi*phi )
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-10*log10( pow(a0+a1+a2, 2) - 4*(a0*a1 + 4*a0*a2 + a1*a2)*phi + 16*a0*a2*phi*phi );
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return dbGain;
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}
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