From 7e5a01f9592be7bfe21b0cb8e534f4c983914ae6 Mon Sep 17 00:00:00 2001
From: Michael Sippel <micha@fragmental.art>
Date: Sun, 12 Jan 2025 05:08:18 +0100
Subject: [PATCH] wip noise gate
---
gate.c | 85 +++++++++++++++++++++++++++++++++++++++++++++++++++++
gate.h | 29 ++++++++++++++++++
guitfx.c | 32 +++++++++++++++++---
meson.build | 1 +
4 files changed, 143 insertions(+), 4 deletions(-)
create mode 100644 gate.c
create mode 100644 gate.h
diff --git a/gate.c b/gate.c
new file mode 100644
index 0000000..9eb0949
--- /dev/null
+++ b/gate.c
@@ -0,0 +1,85 @@
+#include <stdint.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include "gate.h"
+#include <math.h>
+
+void gate_init(
+ struct gate * gate
+) {
+
+ gate->threshold = 0.0;
+ 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;
+}
+
+void gate_process(
+ struct gate * gate,
+ size_t frame_size,
+ float const * in,
+ float * out
+) {
+ float sum = 0.0;
+
+
+ int last_frame = 0;
+
+ for( size_t i = 0; i < frame_size; ++i ) {
+ gate->cur_block_sum += fabs( in[i] );
+ 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);
+
+ if( gate->cur_block_sum > 20.0 ) {
+ gate->is_active = true;
+ } else {
+ gate->is_active = 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 -= 1;
+ }
+ */
+
+
+ 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;
+ }
+}
diff --git a/gate.h b/gate.h
new file mode 100644
index 0000000..9456ccd
--- /dev/null
+++ b/gate.h
@@ -0,0 +1,29 @@
+#pragma once
+
+#include <stdint.h>
+#include <stddef.h>
+#include <stdbool.h>
+
+struct gate {
+ float threshold;
+ bool enable_calibration;
+
+ unsigned block_size;
+
+ unsigned hist_idx;
+ unsigned hist_size;
+ float * hist;
+
+ unsigned cur_block_count;
+ float cur_block_sum;
+
+ bool is_active;
+};
+
+void gate_init();
+void gate_process(
+ struct gate * gate,
+ size_t frame_size,
+ float const * in,
+ float * out
+);
diff --git a/guitfx.c b/guitfx.c
index a512079..824310a 100644
--- a/guitfx.c
+++ b/guitfx.c
@@ -15,8 +15,10 @@
#include "delay.h"
#include "sust.h"
+#include "gate.h"
float envelope( float x );
+
struct data;
struct port {
@@ -34,6 +36,7 @@ struct data {
uint64_t last_tap;
struct delay delay;
struct sust sust;
+ struct gate gate;
unsigned prog;
@@ -100,7 +103,16 @@ static void on_process(void *userdata, struct spa_io_position *position)
break;
case 0x42:
- // sust pedal
+
+ // noise gate calibration
+ if( data->prog == 2 ) {
+ if( midi_data[2] >= 64) {
+ data->gate.threshold = 0.0;//data->gate.cur_avg;
+ printf("calibrate noise gate: threshold = %f\n", data->gate.threshold);
+ }
+ }
+
+ // sust pedal
if( data->prog == 1 ) {
if( midi_data[2] >= 64) {
sust_swap( &data->sust );
@@ -133,6 +145,15 @@ static void on_process(void *userdata, struct spa_io_position *position)
case 0xc0:
// program change
+ if( midi_data[2] >= 64) {
+ sust_swap( &data->sust );
+ data->sust.playing = true;
+
+ data->sust.start_idx = data->sust.idx;
+ data->sust.idx = 0;
+ } else {
+ data->sust.playing = false;
+ }
printf("program change: %u\n", midi_data[1]);
data->prog = midi_data[1];
break;
@@ -155,11 +176,13 @@ static void on_process(void *userdata, struct spa_io_position *position)
float * const in = pw_filter_get_dsp_buffer(data->guit_in_port, n_samples);
- float tmp[n_samples];
+ float tmp1[n_samples];
+ float tmp2[n_samples];
float * out = pw_filter_get_dsp_buffer(data->out_port, n_samples);
if( in && out ) {
- sust_process( &data->sust, n_samples, in, tmp );
- delay_process( &data->delay, n_samples, tmp, out );
+ gate_process( &data->gate, n_samples, in, tmp1 );
+ sust_process( &data->sust, n_samples, tmp1, tmp2 );
+ delay_process( &data->delay, n_samples, tmp2, out );
}
}
@@ -178,6 +201,7 @@ int main(int argc, char *argv[])
{
struct data data = { 0, };
+ gate_init( &data.gate );
delay_init( &data.delay );
sust_init( &data.sust );
data.prog = 0;
diff --git a/meson.build b/meson.build
index 9fc0dd8..d59ef2b 100644
--- a/meson.build
+++ b/meson.build
@@ -9,5 +9,6 @@ executable(
'guitfx.c',
'delay.c',
'sust.c',
+ 'gate.c',
dependencies : [pipewire_dep, m_dep],
)