1 files changed, 27 insertions, 0 deletions
diff --git a/synth/filter.h b/synth/filter.h
new file mode 100644
index 0000000..10db5d7
--- /dev/null
+++ b/synth/filter.h
@@ -0,0 +1,27 @@
+#ifndef __FILTER_H__
+#define __FILTER_H__
+
+#include "fixed.h"
+
+/**
+ * A 24 dB/octave resonant low-pass filter.
+ **/
+class LowPassFilter
+{
+public:
+	LowPassFilter();
+
+	/**
+	 * Reset the filter - clear anything in the delay units of the filter.
+	 */
+	void reset();
+  void set_params(float fc, float res);
+	void	process_sample(fixed_t* smp);
+private:
+	float rate;
+	float nyquist;
+	double d1, d2, d3, d4;
+	double a0, a1, a2, b1, b2;
+};
+
+#endif