start modularization

filter/gain_control.h

@@ -0,0 +1,23 @@
+#pragma once
+#include <math.h>
+
+typedef struct {
+	float targetLevel;
+	float maxGain;
+	float minGain;
+	float attackTime;
+	float releaseTime;
+
+	float currentGain;
+	float currentLevel;
+
+	int sampleRate;
+	float attackCoef;
+	float releaseCoef;
+
+	float rms_buffer;
+	float rmsAlpha;
+} AGC;
+
+void initAGC(AGC* agc, int sampleRate, float targetLevel, float minGain, float maxGain, float attackTime, float releaseTime);
+float process_agc(AGC* agc, float sidechain);