Improved: Parametric filter calculations (command "Filter") are now fully using double precision. This yields a great improvement in signal-to-noise ratio for practically no performance penalty.
Fixed: The method BiQuad::gainAt was returning wrong values. As this method was only used for testing purposes, this change is not user-visible.
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@@ -17,23 +17,20 @@
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51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#define _USE_MATH_DEFINES
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#include <cmath>
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#include <string>
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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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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 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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@@ -52,36 +49,36 @@ BiQuad::BiQuad(Type type, double dbGain, double freq, double srate, double bandw
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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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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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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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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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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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@@ -92,12 +89,12 @@ BiQuad::BiQuad(Type type, double dbGain, double freq, double srate, double bandw
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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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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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@@ -108,20 +105,20 @@ BiQuad::BiQuad(Type type, double dbGain, double freq, double srate, double bandw
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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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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 = float(b0 / a0);
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this->a[0] = float(b1 / a0);
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this->a[1] = float(b2 / a0);
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this->a[2] = float(a1 / a0);
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this->a[3] = float(a2 / a0);
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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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@@ -129,20 +126,20 @@ BiQuad::BiQuad(Type type, double dbGain, double freq, double srate, double bandw
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y2 = 0;
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}
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float BiQuad::gainAt(float freq, float srate)
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double BiQuad::gainAt(double freq, double srate)
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{
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float omega = 2 * (float)M_PI * freq / srate;
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float sn = sin(omega/2.0f);
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float phi = sn * sn;
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float b0 = this->a0;
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float b1 = this->a[0];
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float b2 = this->a[1];
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float a0 = 1.0f;
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float a1 = -this->a[2];
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float a2 = -this->a[3];
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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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float 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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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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}
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