Add resonant filter plugin

src/CMakeLists.txt

@@ -1,3 +1,4 @@
 cmake_minimum_required(VERSION 3.10)
 add_subdirectory(yaw-tab)
 add_subdirectory(yaw-shepard)
+add_subdirectory(yaw-vowel)

src/yaw-vowel/CMakeLists.txt

@@ -4,6 +4,7 @@ dpf_add_plugin(yaw-vowel
   TARGETS vst2
   FILES_DSP
       dsp.cpp
+      filter.cpp
   FILES_UI
       wtutil.cpp
       wintab.cpp

src/yaw-vowel/dsp.cpp

@@ -1,4 +1,5 @@
 #include "DistrhoPlugin.hpp"
+#include "filter.h"
 
 START_NAMESPACE_DISTRHO
 
@@ -7,7 +8,7 @@ class TabPlugin : public Plugin
 public:
 	TabPlugin()
 		: Plugin(kParameterCount, 0, 0),
-		sampleRate(getSampleRate())
+		hzNyq(0.5 * getSampleRate())
 	{
 		// clear all parameters
 		std::memset(fParameters, 0, sizeof(float) * kParameterCount);
@@ -15,13 +16,13 @@ public:
 	}
 
 protected:
-	const char* getLabel() const override { return "yaw-tab"; }
+	const char* getLabel() const override { return "yaw-vowel"; }
 	const char* getDescription() const override { return "Drawing tablet synth UI"; }
 	const char* getMaker() const override { return "yaw-audio"; }
-	const char* getHomePage() const override { return "https://yaw.man/plugins/yaw-tab"; }
-	const char* getLicense() const override { return "ISC"; }
+	const char* getHomePage() const override { return "https://yaw.man/plugins/yaw-vowel"; }
+	const char* getLicense() const override { return "Fuck you pay me"; }
 	uint32_t    getVersion() const override { return d_version(1, 0, 0); }
-	int64_t     getUniqueId() const override { return d_cconst('y', 'w', 't', 'b'); }
+	int64_t     getUniqueId() const override { return d_cconst('y', 'v', 'w', 'l'); }
 
 
 	void initParameter(uint32_t index, Parameter& parameter) override
@@ -69,7 +70,7 @@ protected:
 
 	void sampleRateChanged(double newRate) override
 	{
-		sampleRate = newRate;
+		hzNyq = newRate / 2;
 	}
 
 	float getParameterValue(uint32_t index) const override
@@ -80,49 +81,25 @@ protected:
 	void setParameterValue(uint32_t idx, float val) override
 	{
 		fParameters[idx] = val;
-		switch (idx) {
-		case ktpax:
-			period = 0.02f * val * static_cast<float>(sampleRate);
-			break;
-		case ktpay:
-			break;
-		case ktpaz:
-			break;
-		case ktpap:
-			volume = val;
-			break;
-		case kParameterButtonA:
-			break;
-		case kParameterButtonB:
-			break;
-		}
+		if( kParameterTime == idx ) return;
+		double x = (fParameters[ktpax] * 700.0 + 200.0) / (2.0 * hzNyq);
+		double y = (fParameters[ktpay] * 1900.0 + 500.0) / (2.0 * hzNyq);
+		double p = fParameters[ktpap];
+		filter.set(x, y, p);
 	}
 
 	void run(const float** inputs, float** outputs, uint32_t frames) override
 	{
-
-		for (uint32_t i = 0; i < frames; ++i) {
-			counter++;
-			if (counter > period) {
-				outputs[0][i] = outputs[1][i] = volume;
-				counter = 0;
-			}
-			else {
-				outputs[0][i] = outputs[1][i] = 0.0f;
-			}
-		}
-
+		filter.process(outputs, inputs, frames);
 		parity = !parity;
 		fParameters[kParameterTime] += parity ? 1 : -1;
 	}
 
 private:
 	float fParameters[kParameterCount];
-	float period = 0.f;
-	float counter = 0.f;
-	float volume = 0.f;
-	double sampleRate;
+	double hzNyq;
 	bool parity = false;
+	Filter filter;
 
 	DISTRHO_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR(TabPlugin)
 };

src/yaw-vowel/filter.cpp

@@ -0,0 +1,24 @@
+#include "filter.h"
+
+void Resonator::clear()
+{
+    xp = xpp = yp = ypp = 0;
+}
+
+void Resonator::process(float* output, const float* const input, uint32_t frames)
+{
+  for(uint32_t i = 0; i < frames; ++i){
+    float x = static_cast<float>(input[i] * scale);
+    float y = x - xpp - app * ypp + ap * yp;
+    output[i] = y;
+    xpp = xp;
+    xp = x;
+    ypp = yp;
+    yp = y;
+  }
+}
+
+void Resonator::set(double _app, double _ap, double _scale)
+{
+    app = _app; ap = _ap; scale = _scale;
+}

src/yaw-vowel/filter.h

@@ -0,0 +1,70 @@
+#include "DistrhoPlugin.hpp"
+#include <tuple>
+#include <array>
+
+class Resonator
+{
+public:
+    Resonator():
+    xp(0), xpp(0), yp(0), ypp(0), app(0), ap(0), scale(1){};
+
+    void process(float *output, const float *const input, uint32_t frames);
+    void clear();
+    void set(double _app, double _ap, double _scale);
+
+private:
+    float xp;
+    float xpp;
+    float yp;
+    float ypp;
+    double app;
+    double ap;
+    double scale;
+};
+
+class Filter
+{
+public:
+    Filter(){};
+
+    void process(float **outputs, const float **inputs, uint32_t frames)
+    {
+        for (uint chn = 0; chn < 2; ++chn)
+        {
+            for (uint32_t j = 0; j < frames; ++j)
+            {
+                outputs[chn][j] = inputs[chn][j];
+            }
+            
+            for (auto& r : res[chn])
+            {
+                r.process(outputs[chn], outputs[chn], frames);
+            }
+        }
+
+
+    }
+
+    //Compute filter coefficients from
+    //frequency as a proportion of the sample rate
+    //REMEMBER: THAT'S DOUBLE THE Nyquist RATE, dummy
+    //and resonance in [0, 1]
+    void set(double x, double y, double p)
+    {
+        double r = p * 0.99;
+        double app = r * r;
+        double xap = (1.0 + r * r) * cos(M_PI * x);
+        double yap = (1.0 + r * r) * cos(M_PI * y);
+        double scale = sqrt(0.5 - 0.5 * r * r);
+        for (auto& channelFilter : res)
+        {
+            channelFilter[0].set(app, xap, scale);
+            channelFilter[1].set(app, xap, scale);
+            channelFilter[2].set(app, yap, scale);
+            channelFilter[3].set(app, yap, scale);
+        }
+    }
+
+private:
+    std::array<std::array<Resonator, 4>, 2> res;
+};