From f4bbf94e30fb54e16bfd9fc2cb54284cd885e73b Mon Sep 17 00:00:00 2001
From: Michael Sippel <micha@fragmental.art>
Date: Mon, 27 Jan 2025 21:27:49 +0100
Subject: [PATCH] noise gate: simple attack&release envelope

---
 gate.c | 37 ++++++++++++++++++++++++-------------
 gate.h |  4 ++++
 2 files changed, 28 insertions(+), 13 deletions(-)

diff --git a/gate.c b/gate.c
index 9eb0949..a25a39c 100644
--- a/gate.c
+++ b/gate.c
@@ -8,7 +8,6 @@
 void gate_init(
     struct gate * gate
 ) {
-  
     gate->threshold = 0.0;
     gate->enable_calibration = false;
 
@@ -17,7 +16,12 @@ void gate_init(
     gate->hist_idx = 0;
     gate->hist = malloc( sizeof(float) * gate->hist_size );
     gate->cur_block_count = 0;
-    gate->cur_block_sum = 0.0;    
+    gate->cur_block_sum = 0.0;
+
+    gate->is_active = false;
+    gate->cur_gain = 1.0;
+    gate->attack = 1.0 / 4096.0;
+    gate->release = 1.0 / 4096.0;
 }
 
 void gate_process(
@@ -53,7 +57,7 @@ void gate_process(
 	    last_frame = i;
 	}
     }
-
+    /*
     unsigned enable_pos = gate->is_active ? 0 : frame_size;
     unsigned disable_pos = gate->is_active ? frame_size : 0;
 
@@ -61,8 +65,8 @@ void gate_process(
 
     /* start from last block sum and iterate backwards to find
      * the timepoint where a block sum crosses the threshold
-     */
-    /*
+     * /
+
     unsigned i = gate->hist_idx;
     while( last_frame > 0 ) {
         if( gate->hist[ i ] < gate->threshold ) {
@@ -70,16 +74,23 @@ void gate_process(
         }
 
         last_frame -= gate->block_size;
-        i -= 1;
+        i = (i - 1) % gate->hist_size;
     }
-    */
-
+*/
 
     for( size_t i = 0; i < frame_size; ++i ) {
-      //        if( i >= enable_pos && i < disable_pos )
-        if( gate->is_active )
-            out[i] = in[i];
-	else
-	    out[i] = 0.0;
+        if( gate->is_active ) {
+            gate->cur_gain += gate->attack;
+            if( gate->cur_gain > 1.0 ) {
+                gate->cur_gain = 1.0;
+            }
+        } else {
+            gate->cur_gain -= gate->attack;
+            if( gate->cur_gain < 0.0 ) {
+                gate->cur_gain = 0.0;
+            }
+        }
+
+	out[i] = in[i] * gate->cur_gain;
     }  
 }
diff --git a/gate.h b/gate.h
index 9456ccd..c921d1b 100644
--- a/gate.h
+++ b/gate.h
@@ -18,6 +18,10 @@ struct gate {
   float cur_block_sum;
 
   bool is_active;
+  float cur_gain;
+
+  float attack;
+  float release;
 };
 
 void gate_init();