From e36a4635e8632b12819eac3d1f417c722c00c237 Mon Sep 17 00:00:00 2001
From: Michael Sippel <micha@fragmental.art>
Date: Mon, 27 Jan 2025 23:16:59 +0100
Subject: [PATCH] simplify noise gate

---
 gate.c   | 70 +++++++++++++++-----------------------------------------
 gate.h   |  6 +----
 guitfx.c |  2 +-
 3 files changed, 21 insertions(+), 57 deletions(-)

diff --git a/gate.c b/gate.c
index a25a39c..bb11f25 100644
--- a/gate.c
+++ b/gate.c
@@ -12,15 +12,12 @@ void gate_init(
     gate->enable_calibration = false;
 
     gate->block_size = 1024;
-    gate->hist_size = 256;
-    gate->hist_idx = 0;
-    gate->hist = malloc( sizeof(float) * gate->hist_size );
     gate->cur_block_count = 0;
     gate->cur_block_sum = 0.0;
 
     gate->is_active = false;
     gate->cur_gain = 1.0;
-    gate->attack = 1.0 / 4096.0;
+    gate->attack = 1.0 / 512.0;
     gate->release = 1.0 / 4096.0;
 }
 
@@ -30,67 +27,38 @@ void gate_process(
     float const * in,
     float * out
 ) {
-    float sum = 0.0;
 
-
-    int last_frame = 0;
+  bool act = false;
 
     for( size_t i = 0; i < frame_size; ++i ) {
         gate->cur_block_sum += fabs( in[i] );
-        gate->cur_block_count += 1;
+	gate->cur_block_count += 1;
 
         if( gate->cur_block_count >= gate->block_size ) {
-	  printf("new block sum [%lu] (frame %lu) : %f\n", gate->hist_idx, i, gate->cur_block_sum);
+	  //printf("new block sum %f, gain = %f\n", gate->cur_block_sum, gate->cur_gain);
 
-	  if( gate->cur_block_sum > 20.0 ) {
-	    gate->is_active = true;
+	  gate->last_block_sum = gate->cur_block_sum;
+	  gate->cur_block_sum = 0.0;
+
+	  if( gate->last_block_sum > 0.03 ) {
+              act = true;
 	  } else {
-	    gate->is_active = false;
+              act = false;
 	  }
-
-            gate->hist[ gate->hist_idx ] = gate->cur_block_sum;
-	    gate->hist_idx = (gate->hist_idx + 1) % gate->hist_size;
-            gate->cur_block_sum = 0.0;
-	    gate->cur_block_count = 0;
-
-
-	    last_frame = i;
 	}
-    }
-    /*
-    unsigned enable_pos = gate->is_active ? 0 : frame_size;
-    unsigned disable_pos = gate->is_active ? frame_size : 0;
 
-    unsigned blocks_per_buffer = frame_size / gate->block_size;
-
-    /* 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 ) {
-            disable_pos = last_frame;
-        }
-
-        last_frame -= gate->block_size;
-        i = (i - 1) % gate->hist_size;
-    }
-*/
-
-    for( size_t i = 0; i < frame_size; ++i ) {
-        if( gate->is_active ) {
-            gate->cur_gain += gate->attack;
-            if( gate->cur_gain > 1.0 ) {
+	if( act ) {
+	    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 ) {
+	} else {
+	    gate->cur_gain -= gate->release;
+	    if( gate->cur_gain < 0.0 ) {
                 gate->cur_gain = 0.0;
             }
-        }
+	}
 
-	out[i] = in[i] * gate->cur_gain;
-    }  
+        out[i] = in[i] * gate->cur_gain;
+    }
 }
diff --git a/gate.h b/gate.h
index c921d1b..7f96d6a 100644
--- a/gate.h
+++ b/gate.h
@@ -9,13 +9,9 @@ struct gate {
   bool enable_calibration;
 
   unsigned block_size;
-
-  unsigned hist_idx;
-  unsigned hist_size;
-  float * hist;
-
   unsigned cur_block_count;
   float cur_block_sum;
+  float last_block_sum;
 
   bool is_active;
   float cur_gain;
diff --git a/guitfx.c b/guitfx.c
index 824310a..11ffe2c 100644
--- a/guitfx.c
+++ b/guitfx.c
@@ -107,7 +107,7 @@ static void on_process(void *userdata, struct spa_io_position *position)
 								      // noise gate calibration
 								      if( data->prog == 2 ) {
 									if( midi_data[2] >= 64) {
-									  data->gate.threshold = 0.0;//data->gate.cur_avg;
+									  data->gate.threshold = data->gate.cur_block_sum * 0.8;
 									  printf("calibrate noise gate: threshold = %f\n", data->gate.threshold); 
 									}
 								      }