Added: All remaining filter types (LP(Q), HP(Q), LS(6/12dB), HS(6/12dB), NO, AP) of RoomEQWizard's "Generic" equalizer. Syntax is compatible to REW's filter text file, of course.

2013-05-14 19:22:04 +00:00
1 parent 3dab99a85a
commit e2d5e64f21
@@ -0,0 +1,130 @@
+
+#define _USE_MATH_DEFINES
+#include <cmath>
+#include <string>
+#include "BiQuad.h"
+
+using namespace std;
+
+BiQuad::BiQuad(Type type, float dbGain, float freq, float srate, float bandwidthOrQOrS, bool isBandwidth)
+{
+    float A;
+	if(type == PEAKING || type == LOW_SHELF || type == HIGH_SHELF)
+		A = pow(10, dbGain / 40);
+	else
+		A = pow(10, dbGain / 20);
+    float omega = 2 * (float)M_PI * freq / srate;
+    float sn = sin(omega);
+    float cs = cos(omega);
+	float alpha;
+	float beta = -1;
+
+	if (type == LOW_SHELF || type == HIGH_SHELF) // S
+	{
+		alpha = sn/2 * sqrt((A + 1/A) * (1/bandwidthOrQOrS - 1) + 2);
+		beta = 2 * sqrt(A) * alpha;
+	}
+	else if(isBandwidth) // BW
+		alpha = sn * sinh((float)M_LN2/2 * bandwidthOrQOrS * omega / sn);
+	else // Q
+		alpha = sn / (2 * bandwidthOrQOrS);
+    
+	float b0, b1, b2, a0, a1, a2;
+
+	switch(type)
+	{
+	case LOW_PASS:
+        b0 = (1 - cs) /2;
+        b1 = 1 - cs;
+        b2 = (1 - cs) /2;
+        a0 = 1 + alpha;
+        a1 = -2 * cs;
+        a2 = 1 - alpha;
+		break;
+	case HIGH_PASS:
+        b0 = (1 + cs) /2;
+        b1 = -(1 + cs);
+        b2 = (1 + cs) /2;
+        a0 = 1 + alpha;
+        a1 = -2 * cs;
+        a2 = 1 - alpha;
+		break;
+	case BAND_PASS:
+        b0 = alpha;
+        b1 = 0;
+        b2 = -alpha;
+        a0 = 1 + alpha;
+        a1 = -2 * cs;
+        a2 = 1 - alpha;
+		break;
+	case NOTCH:
+        b0 = 1;
+        b1 = -2 * cs;
+        b2 = 1;
+        a0 = 1 + alpha;
+        a1 = -2 * cs;
+        a2 = 1 - alpha;
+		break;
+	case ALL_PASS:
+		b0 = 1 - alpha;
+		b1 = -2 * cs;
+		b2 = 1 + alpha;
+		a0 = 1 + alpha;
+		a1 = -2 * cs;
+		a2 = 1 - alpha;
+		break;
+	case PEAKING:
+        b0 = 1 + (alpha * A);
+        b1 = -2 * cs;
+        b2 = 1 - (alpha * A);
+        a0 = 1 + (alpha / A);
+        a1 = -2 * cs;
+        a2 = 1 - (alpha / A);
+		break;
+	case LOW_SHELF:
+		b0 = A * ((A + 1) - (A - 1) * cs + beta);
+		b1 = 2 * A * ((A - 1) - (A + 1) * cs);
+		b2 = A * ((A + 1) - (A - 1) * cs - beta);
+		a0 = (A + 1) + (A - 1) * cs + beta;
+		a1 = -2 * ((A - 1) + (A + 1) * cs);
+		a2 = (A + 1) + (A - 1) * cs - beta;
+		break;
+	case HIGH_SHELF:
+        b0 = A * ((A + 1) + (A - 1) * cs + beta);
+        b1 = -2 * A * ((A - 1) + (A + 1) * cs);
+        b2 = A * ((A + 1) + (A - 1) * cs - beta);
+        a0 = (A + 1) - (A - 1) * cs + beta;
+        a1 = 2 * ((A - 1) - (A + 1) * cs);
+        a2 = (A + 1) - (A - 1) * cs - beta;
+		break;
+	}
+
+    this->a0 = b0 /a0;
+    this->a[0] = b1 /a0;
+    this->a[1] = b2 /a0;
+    this->a[2] = -a1 /a0;
+    this->a[3] = -a2 /a0;
+
+	x1 = 0;
+	x2 = 0;
+	y1 = 0;
+	y2 = 0;
+}
+
+float BiQuad::gainAt(float freq, float srate)
+{
+    float omega = 2 * (float)M_PI * freq / srate;
+    float sn = sin(omega/2.0f);
+	float phi = sn * sn;
+	float b0 = this->a0;
+	float b1 = this->a[0];
+	float b2 = this->a[1];
+	float a0 = 1.0f;
+	float a1 = -this->a[2];
+	float a2 = -this->a[3];
+
+	float dbGain = 10*log10( pow(b0+b1+b2, 2) - 4*(b0*b1 + 4*b0*b2 + b1*b2)*phi + 16*b0*b2*phi*phi )
+		-10*log10( pow(a0+a1+a2, 2) - 4*(a0*a1 + 4*a0*a2 + a1*a2)*phi + 16*a0*a2*phi*phi );
+
+	return dbGain;
+}