1 files changed, 46 insertions, 0 deletions
diff --git a/src/lowpass.h b/src/lowpass.h
new file mode 100644
index 0000000..6c99212
--- /dev/null
+++ b/src/lowpass.h
@@ -0,0 +1,46 @@
+#ifndef _LOWPASS_H
+#define _LOWPASS_H
+
+
+/* FILTER INFORMATION STRUCTURE FOR FILTER ROUTINES */
+
+#define FILTER_SECTIONS   2   /* 2 filter sections for 24 db/oct filter */
+
+typedef struct {
+    unsigned int length;       /* size of filter */
+    float history[2 * FILTER_SECTIONS];    /* history in filter */
+    float *coef;               /* pointer to coefficients of filter */
+} FILTER;
+
+typedef struct {
+        double a0, a1, a2;       /* numerator coefficients */
+        double b0, b1, b2;       /* denominator coefficients */
+} BIQUAD;
+
+static BIQUAD ProtoCoef[FILTER_SECTIONS];      /* Filter prototype coefficients,
+                                                     1 for each filter section */
+
+void szxform(
+    double *a0, double *a1, double *a2,     /* numerator coefficients */
+    double *b0, double *b1, double *b2,   /* denominator coefficients */
+    double fc,           /* Filter cutoff frequency */
+    double fs,           /* sampling rate */
+    double *k,           /* overall gain factor */
+    float *coef);         /* pointer to 4 iir coefficients */
+
+
+
+#ifdef __cplusplus
+	extern "C" {
+#endif
+
+	signed char LowPass_Init();
+	void		LowPass_Close();
+	float		LowPass_Filter(float input);
+	void		LowPass_Update(float resonance, float cutoff, int samplerate);
+
+#ifdef __cplusplus
+	}
+#endif
+
+#endif