wip: filter (lp, hp, bp)

inc/BandPassFilter.h

@@ -0,0 +1,12 @@
+#pragma once
+#include "Filter.h"
+
+class BandPassFilter: public Filter
+{
+private:
+    void calculate_coefficients() override;
+public:
+    BandPassFilter(/* args */);
+    ~BandPassFilter();
+};
+

inc/Filter.h

@@ -0,0 +1,32 @@
+#pragma once
+#include "Effect.h"
+
+class Filter: public Effect
+{
+    
+
+protected:
+    struct Normals {
+        float V;
+        float K;
+    };
+
+    float m_freq; // cutoff frequency
+    float m_q; // filter quantity (resonance)
+    float m_order; // filter order (peakGain)
+    /* todo: filter adsr */
+    float m_norm;
+    float m_a0, m_a1, m_a2, m_b1, m_b2;
+    float m_z1, m_z2;
+    Normals calculate_normals();
+    virtual void calculate_coefficients(){};
+public:
+    Filter(/* args */);
+    ~Filter();
+    void Trigger() override;
+    void Release() override;
+    float Process(float in);
+    void Process(std::vector<float>& samples) override;
+    void SetParameters(float freq, float res, float q);
+};
+

inc/HighPassFilter.h

@@ -0,0 +1,12 @@
+#pragma once
+#include "Filter.h"
+
+class HighPassFilter: public Filter
+{
+private:
+    void calculate_coefficients() override;
+public:
+    HighPassFilter(/* args */);
+    ~HighPassFilter();
+};
+

inc/LowPassFilter.h

@@ -0,0 +1,13 @@
+#pragma once
+
+#include "Filter.h"
+
+class LowPassFilter: public Filter
+{
+protected:
+    void calculate_coefficients() override;
+public:
+    LowPassFilter(/* args */);
+    ~LowPassFilter();
+};
+