From a7499201b2de0757eb1db8612edea78c05b0dbe1 Mon Sep 17 00:00:00 2001
From: Jens Ahrensfeld <jens@jayfield.org>
Date: Sun, 9 Nov 2025 19:29:37 +0100
Subject: [PATCH] added feedback

---
 reverb/reverb.hpp | 119 ++++++++++++++++++++++++++++++++--------------
 1 file changed, 83 insertions(+), 36 deletions(-)

diff --git a/reverb/reverb.hpp b/reverb/reverb.hpp
index 227177c..35fd474 100644
--- a/reverb/reverb.hpp
+++ b/reverb/reverb.hpp
@@ -5,29 +5,62 @@
 #include <delay/buffer_multi.hpp>
 #include <common/mix.hpp>
 
+template<typename T, size_t numCh>
+class Delay
+{
+	dsp::BufferMulti<T, numCh> m_buf;
+	int m_delay_spec[numCh];
+
+	public:
+	Delay(uint maxDelaySize, int delayOffset=0)
+	: m_buf(maxDelaySize)
+	{
+		float delayRagePerWindow = (float)(maxDelaySize-delayOffset)/(float)numCh;
+
+		// Delay spec
+		for (int i=0; i < numCh; i++)
+		{
+			float base_delay = i*delayRagePerWindow + delayOffset;
+			float z = (float)rand()/(float)RAND_MAX;
+			int delay = (int)(base_delay + z*delayRagePerWindow);
+
+			m_delay_spec[i] = -delay;
+		}
+	}
+
+	void process(T in, T out[numCh])
+	{
+		m_buf = in;
+		m_buf.quer(out, m_delay_spec);
+		++m_buf;
+	}
+
+	void process(T data[numCh])
+	{
+		m_buf = data;
+		m_buf.quer(data, m_delay_spec);
+		++m_buf;
+	}
+
+	void process(T in[numCh], T out[numCh])
+	{
+		m_buf = in;
+		m_buf.quer(out, m_delay_spec);
+		++m_buf;
+	}
+	
+};
+
 template<typename T, size_t numCh>
 class Diffusor
 {
-	dsp::BufferMulti<T, numCh> m_dly;
-	int m_delay_spec[numCh];
+	Delay<T, numCh> m_dly;
 	int m_shuffle_spec[numCh];
 
 	public:
 	Diffusor(uint maxDelaySize)
 	: m_dly(maxDelaySize)
 	{
-		float delayRagePerWindow = (float)maxDelaySize/(float)numCh;
-
-		// Delay spec
-		for (int i=0; i < numCh; i++)
-		{
-			float base_delay = i*delayRagePerWindow;
-			float z = (float)rand()/(float)RAND_MAX;
-			int delay = (int)(base_delay + z*delayRagePerWindow);
-
-			m_delay_spec[i] = -delay;
-		}
-
 		// Shuffle spec
 		for (int i=0; i < numCh; i++)
 		{
@@ -58,27 +91,22 @@ class Diffusor
 
 	inline T process(T in)
 	{
-		m_dly = in;
+		T temp[numCh];
+		m_dly.process(in, temp);
 
-		T qbuf[numCh];
-		m_dly.quer(qbuf, m_delay_spec);
-		++m_dly;
+		Shuffle<T, numCh>::inPlace(temp, m_shuffle_spec);
+		Hadamard<T, numCh>::inPlace(temp);
+		Householder<T, numCh>::inPlace(temp);
 
-		Shuffle<T, numCh>::inPlace(qbuf, m_shuffle_spec);
-		Hadamard<T, numCh>::inPlace(qbuf);
-		Householder<T, numCh>::inPlace(qbuf);
-
-		return qbuf[0];
+		return temp[0];
 	}
 
-	inline void process_multi(T data[numCh])
+	inline void process_multi(T in_out[numCh])
 	{
-		m_dly = data;
-		m_dly.quer(data, m_delay_spec);
-		++m_dly;
+		m_dly.process(in_out);
 
-		Shuffle<T, numCh>::inPlace(data, m_shuffle_spec);
-		Hadamard<T, numCh>::inPlace(data);
+		Shuffle<T, numCh>::inPlace(in_out, m_shuffle_spec);
+		Hadamard<T, numCh>::inPlace(in_out);
 	}
 
 	static inline void split(T in, T out[numCh])
@@ -89,10 +117,10 @@ class Diffusor
 		}
 	}
 
-	static inline T combine(T data[numCh])
+	static inline T combine(T in_out[numCh])
 	{
-		Householder<T, numCh>::inPlace(data);
-		return data[0];
+		Householder<T, numCh>::inPlace(in_out);
+		return in_out[0];
 	}
 };
 
@@ -100,14 +128,18 @@ template<typename T, uint numCh>
 class Reverb
 {
 	std::array<Diffusor<T, numCh>, 3> m_diffusors;
-	dsp::BufferMulti<T, numCh> m_feedbackDly;
+	Delay<T, numCh> m_feedbackDly;
+	T fb_dly_out[numCh];
 
 	public:
 	Reverb(uint maxDelay)
 	: m_diffusors({maxDelay, maxDelay, maxDelay})
-	, m_feedbackDly(maxDelay)
+	, m_feedbackDly(9600)
 	{
-
+		for (int c=0; c < numCh; c++)
+		{
+			fb_dly_out[c] = 0;
+		}
 	}
 
 	void process_multi(float *in, float *out, unsigned numPoints)
@@ -120,7 +152,22 @@ class Reverb
 			{
 				diffusor.process_multi(temp);
 			}
-			out[i] = Diffusor<T, numCh>::combine(temp);
+			// Sum
+			for (int c=0; c < numCh; c++)
+			{
+				temp[c] += fb_dly_out[c];
+			}
+			m_feedbackDly.process(temp, fb_dly_out);
+			
+			// Mix
+			out[i] = fb_dly_out[0];
+
+			T fb_gain = 0.85;
+			for (int c=0; c < numCh; c++)
+			{
+				fb_dly_out[c] *= fb_gain;
+			}
+			Householder<T, numCh>::inPlace(fb_dly_out);
 		}
 	}