From 3254981cbeb568adfca7991700e92984e0b92f12 Mon Sep 17 00:00:00 2001
From: Dominik Kaiser
Date: Thu, 25 Sep 2025 20:40:18 +0200
Subject: Implement basic CombFilter

---
 src/DSP/CombFilter.cpp  | 20 ++++++++++++++++++++
 src/DSP/CombFilter.h    | 16 ++++++++++++++++
 src/PluginProcessor.cpp |  8 +++++---
 src/PluginProcessor.h   |  4 +++-
 4 files changed, 44 insertions(+), 4 deletions(-)
 create mode 100644 src/DSP/CombFilter.cpp
 create mode 100644 src/DSP/CombFilter.h

(limited to 'src')

diff --git a/src/DSP/CombFilter.cpp b/src/DSP/CombFilter.cpp
new file mode 100644
index 0000000..f7eff21
--- /dev/null
+++ b/src/DSP/CombFilter.cpp
@@ -0,0 +1,20 @@
+#include "CombFilter.h"
+
+void CombFilter::prepare(double sampleRate, int samplesPerBlock) {
+  int maxDelayTimeMs = 100;
+  int maxDelaySamples = static_cast<int>(sampleRate * maxDelayTimeMs / 1000.0);
+
+  delayBuffer.resize(maxDelaySamples, 0.0f);
+  delayInSamples = static_cast<int>(sampleRate * 0.02);
+  delayBufferWritePos = 0;
+}
+
+void CombFilter::process(float* sample) {
+  int delayBufferLength = (int)delayBuffer.size();
+  int delayReadPos = (delayBufferWritePos - delayInSamples + delayBufferLength) % delayBufferLength;
+  float delayedSample = delayBuffer[delayReadPos];
+  float out = *sample + gain * delayedSample;
+  delayBuffer[delayBufferWritePos] = *sample;
+  *sample = out;
+  delayBufferWritePos = (delayBufferWritePos + 1) % delayBufferLength;
+}
diff --git a/src/DSP/CombFilter.h b/src/DSP/CombFilter.h
new file mode 100644
index 0000000..355fbd9
--- /dev/null
+++ b/src/DSP/CombFilter.h
@@ -0,0 +1,16 @@
+#pragma once
+
+#include <juce_audio_processors/juce_audio_processors.h>
+
+class CombFilter {
+public:
+  void prepare(double sampleRate, int samplesPerBlock);
+  void reset();
+  void process(float* sample);
+
+private:
+  std::vector<float> delayBuffer;
+  int delayBufferWritePos = 0;
+  int delayInSamples = 0;
+  float gain = 0.7f;
+};
diff --git a/src/PluginProcessor.cpp b/src/PluginProcessor.cpp
index 825d31a..1b4ada7 100644
--- a/src/PluginProcessor.cpp
+++ b/src/PluginProcessor.cpp
@@ -88,7 +88,7 @@ void SchroederReverbAudioProcessor::prepareToPlay (double sampleRate, int sample
 {
     // Use this method as the place to do any pre-playback
     // initialisation that you need..
-    juce::ignoreUnused (sampleRate, samplesPerBlock);
+    combFilter.prepare(sampleRate, samplesPerBlock);
 }
 
 void SchroederReverbAudioProcessor::releaseResources()
@@ -147,8 +147,10 @@ void SchroederReverbAudioProcessor::processBlock (juce::AudioBuffer<float>& buff
     // interleaved by keeping the same state.
     for (int channel = 0; channel < totalNumInputChannels; ++channel)
     {
-        auto* channelData = buffer.getWritePointer (channel);
-        juce::ignoreUnused (channelData);
+      auto *channelData = buffer.getWritePointer(channel);
+      for (int i = 0; i < buffer.getNumSamples(); ++i) {
+	        combFilter.process(&channelData[i]);
+        }
         // ..do something to the data...
     }
 }
diff --git a/src/PluginProcessor.h b/src/PluginProcessor.h
index 8fcb1e5..ce21b96 100644
--- a/src/PluginProcessor.h
+++ b/src/PluginProcessor.h
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <juce_audio_processors/juce_audio_processors.h>
+#include "DSP/CombFilter.h"
 
 //==============================================================================
 class SchroederReverbAudioProcessor final : public juce::AudioProcessor
@@ -43,6 +44,7 @@ public:
     void setStateInformation (const void* data, int sizeInBytes) override;
 
 private:
-    //==============================================================================
+  //==============================================================================
+  CombFilter combFilter;
     JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (SchroederReverbAudioProcessor)
 };
-- 
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