From bce9ecc2d00cb5213a181f1ea12a47625c5249f6 Mon Sep 17 00:00:00 2001
From: Gordon JC Pearce <gordonjcp@gmail.com>
Date: Sun, 28 Jul 2024 01:40:15 +0100
Subject: [PATCH] Various filters

---
 plugin/barrverb.cpp | 88 +++++++++++++++++++++++++++++++++++++++------
 plugin/barrverb.hpp |  7 ++--
 2 files changed, 83 insertions(+), 12 deletions(-)

diff --git a/plugin/barrverb.cpp b/plugin/barrverb.cpp
index 139be90..5be9d61 100644
--- a/plugin/barrverb.cpp
+++ b/plugin/barrverb.cpp
@@ -20,36 +20,104 @@
 
 START_NAMESPACE_DISTRHO
 
-BarrVerb::BarrVerb() : Plugin(kParameterCount, 1, 0) { // two parameters, one program, no states
-	// dummy
-	deactivate();
+BarrVerb::BarrVerb() : Plugin(kParameterCount, 1, 0) {  // two parameters, one program, no states
+    lowpass = new float[getBufferSize()];
+
+/*
+    // calculate SVF params
+    // hardcoded values for now
+    float fc = 5019;
+    float F = fc / 48000;  // assume 48kHz
+    float w = 2 * tan(3.14159 * F);
+    float a = w / 0.7845;  // 1dB Chebyshev, 2-pole
+    float b = w * w;
+
+    // "corrected" SVF params, per Fons Adriaensen
+    c1_1 = (a + b) / (1 + a / 2 + b / 4);
+    c2_1 = b / (a + b);
+    d0_1 = c1_1 * c2_1 / 4;
+
+    fc = 9433;
+    F = fc / 48000;  // assume 48kHz
+    w = 2 * tan(3.14159 * F);
+    a = w / 3.5594;  // 1dB Chebyshev, 2-pole
+    b = w * w;
+
+    c1_2 = (a + b) / (1 + a / 2 + b / 4);
+    c2_2 = b / (a + b);
+    d0_2 = c1_2 * c2_2 / 4;*/
+        // calculate SVF params
+    // hardcoded values for now
+
+    float fc = 10000;
+    float F = fc / 48000;  // assume 48kHz
+    float w = 2 * tan(3.14159 * F);
+    float a = w / 0.5412;  // 1dB Chebyshev, 2-pole
+    float b = w * w;
+
+    // "corrected" SVF params, per Fons Adriaensen
+    c1_1 = (a + b) / (1 + a / 2 + b / 4);
+    c2_1 = b / (a + b);
+    d0_1 = c1_1 * c2_1 / 4;
+
+    fc = 10000;
+    F = fc / 48000;  // assume 48kHz
+    w = 2 * tan(3.14159 * F);
+    a = w / 1.3065;  // 1dB Chebyshev, 2-pole
+    b = w * w;
+
+    c1_2 = (a + b) / (1 + a / 2 + b / 4);
+    c2_2 = b / (a + b);
+    d0_2 = c1_2 * c2_2 / 4;
 }
 
 // Initialisation functions
 
 void BarrVerb::initAudioPort(bool input, uint32_t index, AudioPort &port) {
-	port.groupId = kPortGroupStereo;
-	Plugin::initAudioPort(input, index, port);
+    port.groupId = kPortGroupStereo;
+    Plugin::initAudioPort(input, index, port);
 }
 
 void BarrVerb::initProgramName(uint32_t index, String &programName) {
-	programName="Default Reverb";
+    programName = "Default Reverb";
 }
 
 // Processing functions
 
 void BarrVerb::activate() {
-	// calculate filter coefficients
+    // calculate filter coefficients
+    printf("called activate()\n");
 }
 
 void BarrVerb::deactivate() {
-	// zero out the outputs, maybe
+    // zero out the outputs, maybe
+    printf("called deactivate()\n");
 }
 
 void BarrVerb::run(const float **inputs, float **outputs, uint32_t frames) {
+    // actual effects here
+
+    float x, o;
+
+    for (uint32_t i = 0; i < frames; i++) {
+        // smash to mono
+        lowpass[i] = (inputs[0][i] + inputs[1][i]) / 2;
+
+        // 10kHz lowpass filter, 2x oversampling
+        x = lowpass[i] - in_z1 - in_z2;
+        in_z2 += c2_1 * in_z1;
+        in_z1 += c1_1 * x;
+
+        x = (d0_1 * x + in_z2) - in_z12 - in_z22;
+        in_z22 += c2_2 * in_z12;
+        in_z12 += c1_2 * x;
+        lowpass[i] = d0_2 * x + in_z22;
+
+        outputs[0][i] = lowpass[i];
+        outputs[1][i] = lowpass[i];
+    }
 }
 
 // create the plugin
-Plugin* createPlugin() { return new BarrVerb(); }
+Plugin *createPlugin() { return new BarrVerb(); }
 END_NAMESPACE_DISTRHO
-
diff --git a/plugin/barrverb.hpp b/plugin/barrverb.hpp
index 9543c6c..5cd8285 100644
--- a/plugin/barrverb.hpp
+++ b/plugin/barrverb.hpp
@@ -45,14 +45,17 @@ class BarrVerb : public Plugin {
     // Initialisation
     void initAudioPort(bool input, uint32_t index, AudioPort &port) override;
     void initProgramName(uint32_t index, String &programName) override;
-
+    
     // Processing
     void activate() override;
     void deactivate() override;
     void run(const float **inputs, float **outputs, uint32_t frames) override;
 
    private:
-    float c1, c2, d0, in_z1, in_z2, out_z1, out_z2;
+    float c1_1, c2_1, d0_1, c1_2, c2_2, d0_2, in_z1, in_z2, in_z12,in_z22, out_z1, out_z2;
+
+    float *lowpass;
+
 
     DISTRHO_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR(BarrVerb);
 };