AnalogTapeModel

commit 149734501e3cadeab3c6143f5a4d4704ffcb5d29
parent acdc5c3a9641390fafcd962622d3f8ddaf60537a
Author: jatinchowdhury18 <jatinchowdhury18@gmail.com>
Date:   Tue,  7 Sep 2021 14:53:53 -0700

Use 12 dB/Oct instead of 24 dB/Oct for DC blocking filters (#218)


Diffstat:
M
Plugin/Source/Processors/Hysteresis/DCBlocker.h
 | 
19
+++++++++----------
M
Plugin/Source/Processors/Timing_Effects/WowFlutterProcessor.cpp
 | 
2
+-

2 files changed, 10 insertions(+), 11 deletions(-)
diff --git a/Plugin/Source/Processors/Hysteresis/DCBlocker.h b/Plugin/Source/Processors/Hysteresis/DCBlocker.h
@@ -15,8 +15,8 @@ public:
       */
     void prepare (double sampleRate, float dcFreq)
     {
-        hpf[0].reset();
-        hpf[1].reset();
+        for (auto& filt : hpf)
+            filt.reset();
 
         fs = (float) sampleRate;
 
@@ -25,9 +25,7 @@ public:
 
     void calcCoefs (float fc)
     {
-        // Q values for 4th-order Butterworth filter
-        // (https://en.wikipedia.org/wiki/Butterworth_filter#Normalized_Butterworth_polynomials)
-        constexpr float Qs[] = { 1.0f / 0.7654f, 1.0f / 1.8478f };
+        const static auto butterQs = chowdsp::QValCalcs::butterworth_Qs<float, 2 * NFilt>();
 
         float wc = MathConstants<float>::twoPi * fc / fs;
         float c = 1.0f / dsp::FastMathApproximations::tan (wc / 2.0f);
@@ -35,9 +33,9 @@ public:
 
         float b[3];
         float a[3];
-        for (int i = 0; i < 2; ++i)
+        for (int i = 0; i < NFilt; ++i)
         {
-            float K = c / Qs[i];
+            float K = c / butterQs[i];
             float a0 = phi + K + 1.0f;
 
             b[0] = phi / a0;
@@ -52,12 +50,13 @@ public:
 
     void processBlock (float* buffer, const int numSamples)
     {
-        hpf[0].processBlock (buffer, numSamples);
-        hpf[1].processBlock (buffer, numSamples);
+        for (auto& filt : hpf)
+            filt.processBlock (buffer, numSamples);
     }
 
 private:
-    chowdsp::IIRFilter<2> hpf[2];
+    static constexpr int NFilt = 1;
+    std::array<chowdsp::IIRFilter<2>, NFilt> hpf;
 
     float fs = 44100.0f;
 
diff --git a/Plugin/Source/Processors/Timing_Effects/WowFlutterProcessor.cpp b/Plugin/Source/Processors/Timing_Effects/WowFlutterProcessor.cpp
@@ -49,7 +49,7 @@ void WowFlutterProcessor::prepareToPlay (double sampleRate, int samplesPerBlock)
         delay.prepare ({ sampleRate, (uint32) samplesPerBlock, 2 });
         delay.setDelay (0.0f);
 
-        dcBlocker[ch].prepare (sampleRate, 15.0f);
+        dcBlocker[ch].prepare (sampleRate, 20.0f);
     }
 
     wowPlot->prepareToPlay (sampleRate, samplesPerBlock);