formatting cleanup

plugin/module.cpp

@@ -74,7 +74,7 @@ void Module::run(Voice* voices, uint32_t blockSize) {
     sub = patchRam.sub / 127.0f;
     lfoPhase += lfoRateTable[patchRam.lfoRate];
 
-    res = patchRam.vcfReso / 127.0 * 5;
+    res = patchRam.vcfReso / 127.0;
     noise = patchRam.noise / 127.0;
 
     // FIXME the exp in these is expensive, don't call it all the time

plugin/module.hpp

@@ -48,26 +48,74 @@ class Module {
 
     float saw = 0, square = 0, sub = 0, noise = 0;
 
+    /*
+    #if 0
+        struct {
+            uint8_t lfoRate = 0x58;
+            uint8_t lfoDelay = 0x00;
+            uint8_t vcoLfo = 0x00;
+            uint8_t pwmLfo = 0x3b;
+            uint8_t noise = 0x00;
+            uint8_t vcfFreq = 0x25;  // 1c;  // 0x3f80
+            uint8_t vcfReso = 0x6a;
+            uint8_t vcfEnv = 0x25;  // 4e;
+            uint8_t vcfLfo = 0x00;
+            uint8_t vcfKey = 0x00;  // 47;
+            uint8_t vca = 0x35;
+            uint8_t env_a = 0x00;
+            uint8_t env_d = 0x3c;
+            uint8_t env_s = 0x00;  // 0x3f80
+            uint8_t env_r = 0x3c;
+            uint8_t sub = 0x7f;
+            uint8_t switch1 = 0x4a;
+            uint8_t switch2 = 0x18;
+        } patchRam;
+
+    #else
+        struct {
+            uint8_t lfoRate = 0x40;
+            uint8_t lfoDelay = 0x00;
+            uint8_t vcoLfo = 0x00;
+            uint8_t pwmLfo = 0x00;
+            uint8_t noise = 0x01;
+            uint8_t vcfFreq = 0x31;
+            uint8_t vcfReso = 0x7f;
+            uint8_t vcfEnv = 0x00;
+            uint8_t vcfLfo = 0x00;
+            uint8_t vcfKey = 0x7f;
+            uint8_t vca = 0x40;
+            uint8_t env_a = 0x00;
+            uint8_t env_d = 0x00;
+            uint8_t env_s = 0x00;  // 0x3f80
+            uint8_t env_r = 0x00;
+            uint8_t sub = 0x00;
+            uint8_t switch1 = 0x22;
+            uint8_t switch2 = 0x1d;
+        } patchRam;
+    #endif
+    */
+
     struct {
-                uint8_t lfoRate = 0x58;
+        uint8_t lfoRate = 0x58;
         uint8_t lfoDelay = 0x00;
         uint8_t vcoLfo = 0x00;
-        uint8_t pwmLfo = 0x3b;
+        uint8_t pwmLfo = 0x00;
         uint8_t noise = 0x00;
-        uint8_t vcfFreq = 0x25;  // 1c;  // 0x3f80
-        uint8_t vcfReso = 0x6a;
-        uint8_t vcfEnv = 0x25;  // 4e;
+        uint8_t vcfFreq = 0x00;  // 1c;  // 0x3f80
+        uint8_t vcfReso = 0x7f;
+        uint8_t vcfEnv = 0x7f;  // 4e;
         uint8_t vcfLfo = 0x00;
         uint8_t vcfKey = 0x00;  // 47;
-        uint8_t vca = 0x35;
+        uint8_t vca = 0x20;
         uint8_t env_a = 0x00;
-        uint8_t env_d = 0x3c;
+        uint8_t env_d = 0x5c;
         uint8_t env_s = 0x00;  // 0x3f80
         uint8_t env_r = 0x3c;
         uint8_t sub = 0x7f;
-        uint8_t switch1 = 0x4a;
-        uint8_t switch2 = 0x18;
+        uint8_t switch1 = 0x3a;
+        uint8_t switch2 = 0x19;
     } patchRam;
+
     Chorus* chorus;
 
     float vcaTC;
@@ -104,14 +152,16 @@ class Voice {
 
     uint8_t envPhase = 0;
     int16_t env = 0;  // output amplitude
-    int16_t vcfCut;
+    uint16_t vcfCut;
     int16_t vcaEnv;
     float vcaRC = 0, vcfRC = 0;
 
     uint8_t note = 0;
 
     // filter
-    float b1 = 0, b2 = 0, b3 = 0, b4 = 0;
+    float y0 = 0, y1 = 0, y2 = 0, y3 = 0;
+    double s[4] = {0, 0, 0, 0};
+    float zi = 0;
 };
 
 #endif

plugin/voice.cpp

@@ -41,7 +41,7 @@ Voice::Voice() {
 
 void Voice::on(uint8_t midiNote) {
     while (midiNote < 24) midiNote += 12;
-    while (midiNote > 108) midiNote -=12;
+    while (midiNote > 108) midiNote -= 12;
     note = midiNote - 24;
     envPhase = 1;
 }
@@ -50,15 +50,26 @@ void Voice::off() {
     envPhase = 0;
 }
 
+// tanh(x)/x approximation, flatline at very high inputs
+// so might not be safe for very large feedback gains
+// [limit is 1/15 so very large means ~15 or +23dB]
+
+double tanhXdX(double x) {
+    float s = 0.0333, d = 30.0;
+    return 1.0f - s * (d + 1.0f) * x * x / (d + x * x);
+
+}
+
 void Voice::run(Module* m, float* buffer, uint32_t samples) {
     // carry out per-voice calculations for each block of samples
     float out, t, fb;
 
-    // FIXME incorrect
     // calculate cutoff frequency
-    float cut = 248.0f * (powf(2, (vcfCut - 0x1880) / 1143.0f));
-    cut = 0.25 * 6.2832 * cut / 48000.0f;  // FIXME hardcoded values
-    cut = cut / (1 + cut);                 // correct tuning warp
+    float cut = 261.0f * (powf(2, (vcfCut - 0x1880) / 1143.0f));
+    cut = M_PI * cut / sampleRate;
+    cut = cut / (1 + cut);  // correct tuning warp
+    // if (cut > 0.7) cut = 0.7;
+    double r = 5 * m->res;
 
     float amp = vcaEnv / 4096.0f;
 
@@ -95,31 +106,104 @@ void Voice::run(Module* m, float* buffer, uint32_t samples) {
         // FIXME DC offset removal
         delay += m->saw * (1 - (2 * theta));
         delay += m->square * ((pulseStage ? -1.f : 1.f) - m->pwmBuf[i] + 0.5);
-        delay += m->subBuf[i] * subosc ;
+        delay += m->subBuf[i] * subosc;
 
         out += m->noise * (0.8 - 1.6 * (rand() & 0xffff) / 65536.0);
-        out *= 0.5;
+        // out *= 0.1;
 
         // same time constant for both VCF and VCF RC circuits
         vcfRC = (cut - vcfRC) * m->vcaTC + vcfRC;
 
-        for (uint8_t ovs = 0; ovs < 4; ovs++) {
-            fb = b4;
+#if 1
+
+        //// LICENSE TERMS: Copyright 2012 Teemu Voipio
+        //
+        // You can use this however you like for pretty much any purpose,
+        // as long as you don't claim you wrote it. There is no warranty.
+        //
+        // Distribution of substantial portions of this code in source form
+        // must include this copyright notice and list of conditions.
+        //
+
+        // input delay and state for member variables
+
+        // cutoff as normalized frequency (eg 0.5 = Nyquist)
+        // resonance from 0 to 1, self-oscillates at settings over 0.9
+        // void transistorLadder(
+        //    double cutoff, double resonance,
+        //    double * in, double * out, unsigned nsamples)
+        //{
+        // tuning and feedback
+
+        //------------------------------------------------------------------------------ sample loop
+        // for(unsigned n = 0; n < nsamples; ++n)
+        //{
+
+        out *= 0.025;
+        // input with half delay, for non-linearities
+        double ih = 0.5 * (out + zi);
+        zi = out;
+
+        // double ih = out;
+
+        // evaluate the non-linear gains
+        double t0 = tanhXdX((ih * (r + 1)) - r * s[3]);
+
+        double t1 = tanhXdX(s[0]);
+        double t2 = tanhXdX(s[1]);
+        double t3 = tanhXdX(s[2]);
+        double t4 = tanhXdX(s[3]);
+
+        double f = vcfRC;
+
+        // g# the denominators for solutions of individual stages
+        double g0 = 1 / (1 + f * t1), g1 = 1 / (1 + f * t2);
+        double g2 = 1 / (1 + f * t3), g3 = 1 / (1 + f * t4);
+
+        // f# are just factored out of the feedback solution
+        double f3 = f * t3 * g3, f2 = f * t2 * g2 * f3, f1 = f * t1 * g1 * f2, f0 = f * t0 * g0 * f1;
+
+        // solve feedback
+        double y3 = (g3 * s[3] + f3 * g2 * s[2] + f2 * g1 * s[1] + f1 * g0 * s[0] + f0 * out) / (1 + r * f0);
+
+        // then solve the remaining outputs (with the non-linear gains here)
+        double xx = t0 * ((out * (r + 1)) - r * y3);
+        double y0 = t1 * g0 * (s[0] + f * xx);
+        double y1 = t2 * g1 * (s[1] + f * y0);
+        double y2 = t3 * g2 * (s[2] + f * y1);
+
+        // update state
+        s[0] += 2 * f * (xx - y0);
+        s[1] += 2 * f * (y0 - y1);
+        s[2] += 2 * f * (y1 - y2);
+        s[3] += 2 * f * (y2 - t4 * y3);
+
+        // out[n] = y3;
+        // }
+        // out *= 0.1;
+
+        out = y3;
+
+#else
+
+        out *= 0.5;
+        for (uint8_t ovs = 0; ovs < 2; ovs++) {
+            fb = y3;
             // hard clip
-            fb = ((out * 0.5) - fb) * m->res;
+            fb = ((out * 0.5) - fb) * r;
             if (fb > 4) fb = 4;
             if (fb < -4) fb = -4;
             // fb = 1.5 * fb - 0.5 * fb * fb * fb;
             //
 
-            b1 = ((out + fb - b1) * vcfRC) + b1;
-            b2 = ((b1 - b2) * vcfRC) + b2;
-            b3 = ((b2 - b3) * vcfRC) + b3;
-            b4 = ((b3 - b4) * vcfRC) + b4;
+            y0 = ((out + fb - y0) * vcfRC) + y0;
+            y1 = ((y0 - y1) * vcfRC) + y1;
+            y2 = ((y1 - y2) * vcfRC) + y2;
+            y3 = ((y2 - y3) * vcfRC) + y3;
         }
-
+#endif
         vcaRC = (amp - vcaRC) * m->vcaTC + vcaRC;
-        buffer[i] += 0.09367 * m->vcaBuf[i] * vcaRC * b4;
+        buffer[i] += m->vcaBuf[i] * vcaRC * out;
 
         lastpw = m->pwmBuf[i];
     }