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.

BiQuad.h

@@ -0,0 +1,72 @@
+/*
+	This file is part of EqualizerAPO, a system-wide equalizer.
+	Copyright (C) 2013  Jonas Thedering
+
+	This program is free software; you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation; either version 2 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License along
+	with this program; if not, write to the Free Software Foundation, Inc.,
+	51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+#include <string>
+
+#define IS_DENORMAL(f) (((*(unsigned int *)&(f))&0x7f800000) == 0)
+
+class BiQuad
+{
+public:
+	enum Type
+	{
+		LOW_PASS, HIGH_PASS, BAND_PASS, NOTCH, ALL_PASS, PEAKING, LOW_SHELF, HIGH_SHELF
+	};
+
+	BiQuad() {}
+	BiQuad(Type type, float dbGain, float freq, float srate, float bandwidthOrQOrS, bool isBandwidth);
+
+	__forceinline
+	void removeDenormals()
+	{
+		if(IS_DENORMAL(x1))
+			x1 = 0.0f;
+		if(IS_DENORMAL(x2))
+			x2 = 0.0f;
+		if(IS_DENORMAL(y1))
+			y1 = 0.0f;
+		if(IS_DENORMAL(y2))
+			y2 = 0.0f;
+	}
+
+	__forceinline
+	float process(float sample)
+	{
+		float result = a0 * sample + a[0] * x1 + a[1] * x2 +
+			a[2] * y1 + a[3] * y2;
+
+		x2 = x1;
+		x1 = sample;
+
+		y2 = y1;
+		y1 = result;
+
+		//Input for next stage
+		return result;
+	}
+
+	float gainAt(float freq, float srate);
+
+private:
+	__declspec(align(16)) float a[4];
+	float a0;
+
+	float x1, x2;
+	float y1, y2;
+};