diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..dee53c5
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+build
+*~
diff --git a/controller.c b/controller.c
new file mode 100644
index 0000000..76e38b7
--- /dev/null
+++ b/controller.c
@@ -0,0 +1,110 @@
+#include "pipewire/keys.h"
+#include "pipewire/port.h"
+#include "spa/pod/iter.h"
+#include "spa/utils/defs.h"
+#include <signal.h>
+#include <stdio.h>
+
+#include <spa/control/control.h>
+#include <spa/param/latency-utils.h>
+#include <spa/pod/builder.h>
+#include <spa/pod/pod.h>
+
+#include <pipewire/filter.h>
+#include <pipewire/pipewire.h>
+
+#include "guitfx.h"
+#include "delay.h"
+#include "sust.h"
+#include "gate.h"
+
+void midi_control(
+ struct FxData * data,
+
+ uint64_t frame,
+ uint64_t offset,
+ unsigned sec,
+ unsigned midi_size,
+ uint8_t * midi_data,
+ struct spa_io_position* position
+) {
+ printf("[%d] MIDI message (%d bytes) : %x, %x, %x\n", sec, midi_size,
+ midi_data[0], midi_data[1], midi_data[2]);
+
+ switch (midi_data[0] & 0xff) {
+ case 0xb0:
+ switch (midi_data[1]) {
+ case 0x0b:
+ // expr pedal
+ float val_f = ((float)midi_data[2]) / 128.0;
+
+ float thres = 0.5;
+
+ if (val_f > thres) {
+ float expr_mix = (val_f - thres) / (1.0 - thres);
+ printf("Expr Pedal %f\n", expr_mix);
+
+ data->delay.mix = expr_mix;
+ } else {
+ data->delay.mix = 0.0;
+ }
+ break;
+
+ case 0x42:
+
+ // noise gate calibration
+ if (data->prog == 2) {
+ if (midi_data[2] >= 64) {
+ data->gate.threshold = data->gate.cur_block_sum * 0.8;
+ 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);
+ data->sust.playing = true;
+
+ data->sust.start_idx = data->sust.idx;
+ data->sust.idx = 0;
+ } else {
+ data->sust.playing = false;
+ }
+ }
+
+ // tap tempo
+ if (data->prog == 0) {
+ uint64_t cur_tap = frame + offset;
+ uint64_t duration = cur_tap - data->last_tap;
+ data->last_tap = cur_tap;
+ if (duration < (4 * position->clock.rate.denom)) {
+ delay_set_time(&data->delay, duration);
+ }
+
+ sust_resize(&data->sust, duration);
+ }
+
+ break;
+ }
+
+ break;
+
+ 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;
+ }
+}
+
diff --git a/delay.c b/delay.c
index c99b818..1723ca9 100644
--- a/delay.c
+++ b/delay.c
@@ -1,12 +1,12 @@
-#include <stdint.h>
-#include <stddef.h>
-#include <stdlib.h>
-#include <stdio.h>
#include "delay.h"
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
void delay_init(
- struct delay * delay
-) {
+ struct delay* delay)
+{
delay->mix = 0.8;
delay->feedback = 0.8;
delay->duration = 0;
@@ -16,39 +16,38 @@ void delay_init(
}
void delay_set_time(
- struct delay * delay,
- uint64_t new_duration
-) {
+ struct delay* delay,
+ uint64_t new_duration)
+{
printf("set delay duration to %lu samples\n", new_duration);
- if( new_duration > delay->buf_capacity ) {
+ if (new_duration > delay->buf_capacity) {
delay->buf_capacity = new_duration;
- delay->buf = realloc( delay->buf, sizeof(float) * new_duration );
+ delay->buf = realloc(delay->buf, sizeof(float) * new_duration);
}
- for( int i = delay->duration; i < new_duration; ++i ) {
+ for (int i = delay->duration; i < new_duration; ++i) {
delay->buf[i] = delay->buf[i - delay->duration];
}
delay->duration = new_duration;
- if( new_duration > 0 ) {
+ if (new_duration > 0) {
delay->buf_idx %= new_duration;
}
}
void delay_process(
- struct delay * delay,
+ struct delay* delay,
size_t frame_size,
- float const * in,
- float * out
-) {
- for( size_t i = 0; i < frame_size; ++i ) {
- if( delay->duration > 0 ) {
- out[i] =
- 0.5 * in[i]
- + 0.5 * delay->mix * delay->buf[ delay->buf_idx ];
+ float const* in,
+ float* out)
+{
+ for (size_t i = 0; i < frame_size; ++i) {
+ if (delay->duration > 0) {
+ out[i] = in[i]
+ + delay->mix * delay->buf[delay->buf_idx];
- delay->buf[ delay->buf_idx ] *= delay->feedback;
- delay->buf[ delay->buf_idx ] += (1.0 - delay->feedback) * in[i];
+ delay->buf[delay->buf_idx] *= delay->feedback;
+ delay->buf[delay->buf_idx] += (1.0 - delay->feedback) * in[i];
delay->buf_idx = (delay->buf_idx + 1) % delay->duration;
} else {
out[i] = 0.5 * in[i];
diff --git a/delay.h b/delay.h
index 4ed2cf5..499b1cc 100644
--- a/delay.h
+++ b/delay.h
@@ -1,7 +1,7 @@
#pragma once
-#include <stdint.h>
#include <stddef.h>
+#include <stdint.h>
struct delay {
uint64_t duration;
@@ -10,21 +10,18 @@ struct delay {
uint64_t buf_idx;
size_t buf_capacity;
- float * buf;
+ float* buf;
};
void delay_init(
- struct delay * delay
-);
+ struct delay* delay);
void delay_set_time(
- struct delay * delay,
- uint64_t new_duration
-);
+ struct delay* delay,
+ uint64_t new_duration);
void delay_process(
- struct delay * delay,
+ struct delay* delay,
size_t frame_size,
- float const * in,
- float * out
-);
+ float const* in,
+ float* out);
diff --git a/gate.c b/gate.c
new file mode 100644
index 0000000..3f13c6a
--- /dev/null
+++ b/gate.c
@@ -0,0 +1,64 @@
+#include "gate.h"
+#include <math.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+void gate_init(
+ struct gate* gate)
+{
+ gate->threshold = 0.0;
+ gate->enable_calibration = false;
+
+ gate->block_size = 1024;
+ gate->cur_block_count = 0;
+ gate->cur_block_sum = 0.0;
+
+ gate->is_active = false;
+ gate->cur_gain = 1.0;
+ gate->attack = 1.0 / 128.0;
+ gate->release = 1.0 / 8192.0;
+}
+
+void gate_process(
+ struct gate* gate,
+ size_t frame_size,
+ float const* in,
+ float* out)
+{
+
+ bool act = false;
+
+ 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 %f, gain = %f\n", gate->cur_block_sum, gate->cur_gain);
+
+ gate->last_block_sum = gate->cur_block_sum;
+ gate->cur_block_sum = 0.0;
+
+ if (gate->last_block_sum > 0.03) {
+ act = true;
+ } else {
+ act = false;
+ }
+ }
+
+ if (act) {
+ gate->cur_gain += gate->attack;
+ if (gate->cur_gain > 1.0) {
+ gate->cur_gain = 1.0;
+ }
+ } else {
+ gate->cur_gain -= gate->release;
+ if (gate->cur_gain < 0.0) {
+ gate->cur_gain = 0.0;
+ }
+ }
+
+ out[i] = in[i] * gate->cur_gain;
+ }
+}
diff --git a/gate.h b/gate.h
new file mode 100644
index 0000000..3773e5c
--- /dev/null
+++ b/gate.h
@@ -0,0 +1,28 @@
+#pragma once
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+struct gate {
+ float threshold;
+ bool enable_calibration;
+
+ unsigned block_size;
+ unsigned cur_block_count;
+ float cur_block_sum;
+ float last_block_sum;
+
+ bool is_active;
+ float cur_gain;
+
+ float attack;
+ float release;
+};
+
+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 02f8a12..82b53ca 100644
--- a/guitfx.c
+++ b/guitfx.c
@@ -2,223 +2,186 @@
#include "pipewire/port.h"
#include "spa/pod/iter.h"
#include "spa/utils/defs.h"
-#include <stdio.h>
#include <signal.h>
+#include <stdio.h>
-#include <spa/pod/pod.h>
-#include <spa/pod/builder.h>
#include <spa/control/control.h>
#include <spa/param/latency-utils.h>
+#include <spa/pod/builder.h>
+#include <spa/pod/pod.h>
-#include <pipewire/pipewire.h>
#include <pipewire/filter.h>
+#include <pipewire/pipewire.h>
#include "delay.h"
+#include "gate.h"
+#include "sust.h"
+#include "guitfx.h"
+
+float envelope(float x);
struct data;
struct port {
- struct data *data;
+ struct data* data;
};
+void midi_control(
+ struct FxData * data,
+
+ uint64_t frame,
+ uint64_t offset,
+ unsigned sec,
+ unsigned midi_size,
+ uint8_t * midi_data,
+ struct spa_io_position* position);
+
+
struct data {
- struct pw_main_loop * loop;
- struct pw_filter * filter;
- struct port * guit_in_port;
- struct port * midi_in_port;
- struct port * out_port;
-
- //! effect data
- uint64_t last_tap;
- struct delay delay;
-
- //! elapsed time in number of samples
- uint64_t time;
+ struct pw_main_loop* loop;
+ struct pw_filter* filter;
+ struct port* guit_in_port;
+ struct port* midi_in_port;
+ struct port* out_port;
+ struct FxData fx_data;
};
-static void on_process(void *userdata, struct spa_io_position *position)
+static void on_process(void* userdata, struct spa_io_position* position)
{
- struct data *data = userdata;
+ struct data* data = userdata;
- uint32_t n_samples = position->clock.duration;
- uint64_t frame = data->time;
- data->time += n_samples;
+ uint32_t n_samples = position->clock.duration;
+ uint64_t frame = data->fx_data.time;
+ data->fx_data.time += n_samples;
- struct pw_buffer * b = pw_filter_dequeue_buffer(data->midi_in_port);
- if( b == NULL ) {
- fprintf(stderr, "on_process(): no buffer for midi_in_port\n");
- return;
- }
+ struct pw_buffer* b = pw_filter_dequeue_buffer(data->midi_in_port);
+ if (b == NULL) {
+ fprintf(stderr, "on_process(): no buffer for midi_in_port\n");
+ return;
+ }
- struct spa_buffer * buf = b->buffer;
- spa_assert(buf->n_datas == 1);
- struct spa_data * d = &buf->datas[0];
+ struct spa_buffer* buf = b->buffer;
+ spa_assert(buf->n_datas == 1);
+ struct spa_data* d = &buf->datas[0];
- if( d->data ) {
- struct spa_pod * pod =
- spa_pod_from_data(
- d->data,
- d->maxsize,
- d->chunk->offset,
- d->chunk->size
- );
+ if (d->data) {
+ struct spa_pod* pod = spa_pod_from_data(d->data, d->maxsize,
+ d->chunk->offset, d->chunk->size);
- if( pod ) {
- if( spa_pod_is_sequence(pod) ) {
- struct spa_pod_sequence * pod_seq = (struct spa_pod_sequence*) pod;
- struct spa_pod_control * c;
- SPA_POD_SEQUENCE_FOREACH(pod_seq, c) {
- if( c->type == SPA_CONTROL_Midi ) {
- unsigned sec =
- (frame + c->offset)
- / (float) position->clock.rate.denom;
- char * midi_data = SPA_POD_BODY(&c->value);
- unsigned size = SPA_POD_BODY_SIZE(&c->value);
+ if (pod) {
+ if (spa_pod_is_sequence(pod)) {
+ struct spa_pod_sequence* pod_seq = (struct spa_pod_sequence*)pod;
+ struct spa_pod_control* c;
+ SPA_POD_SEQUENCE_FOREACH(pod_seq, c)
+ {
+ if (c->type == SPA_CONTROL_Midi) {
+ unsigned sec = (frame + c->offset) / (float)position->clock.rate.denom;
+ char* midi_data = SPA_POD_BODY(&c->value);
+ unsigned midi_size = SPA_POD_BODY_SIZE(&c->value);
- printf("[%d] MIDI message (%d bytes) : %x, %x, %x\n", sec, size, midi_data[0], midi_data[1], midi_data[2]);
+ midi_control( &data->fx_data, frame, c->offset, sec, midi_size, midi_data, position );
+ } else {
- switch( midi_data[0] & 0xff ) {
- case 0xb0:
- switch( midi_data[1] ) {
- case 0x0b:
- // expr pedal
- float val_f = ((float)midi_data[2]) / 128.0;
- printf("Expr Pedal %f\n", val_f);
+ printf("on_process(): non midi-control\n");
+ }
+ }
+ } else {
+ fprintf(stderr, "on_process(): unexpected POD that is not a sequence "
+ "(midi_in_port)\n");
+ }
+ } else {
+ fprintf(stderr, "on_process(): pod is NULL\n");
+ }
+ } else {
+ fprintf(stderr, "on_process(): no data in buffer of midi_in_port\n");
+ }
- data->delay.mix = val_f;
- break;
+ pw_filter_queue_buffer(data->midi_in_port, b);
- case 0x42:
- // sust pedal
-
- uint64_t cur_tap = frame + c->offset;
- uint64_t duration = cur_tap - data->last_tap;
- data->last_tap = cur_tap;
- if( duration < (4*position->clock.rate.denom) ) {
- delay_set_time( &data->delay, duration/4 );
- }
- break;
- }
- break;
-
- case 0xc0:
- // program change
- printf("program change: %u\n", midi_data[1]);
- break;
- }
- } else {
- printf("on_process(): non midi-control\n");
- }
- }
- } else {
- fprintf(stderr, "on_process(): unexpected POD that is not a sequence (midi_in_port)\n");
- }
- } else {
- fprintf(stderr, "on_process(): pod is NULL\n");
- }
- } else {
- fprintf(stderr, "on_process(): no data in buffer of midi_in_port\n");
- }
-
- pw_filter_queue_buffer(data->midi_in_port, b);
-
-
- float * const in = pw_filter_get_dsp_buffer(data->guit_in_port, n_samples);
- float * out = pw_filter_get_dsp_buffer(data->out_port, n_samples);
- if( in && out ) {
- delay_process( &data->delay, n_samples, in, out );
- }
+ float* const in = pw_filter_get_dsp_buffer(data->guit_in_port, 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) {
+ gate_process(&data->fx_data.gate, n_samples, in, tmp1);
+ sust_process(&data->fx_data.sust, n_samples, tmp1, tmp2);
+ delay_process(&data->fx_data.delay, n_samples, tmp2, out);
+ }
}
static const struct pw_filter_events filter_events = {
- PW_VERSION_FILTER_EVENTS,
- .process = on_process,
+ PW_VERSION_FILTER_EVENTS,
+ .process = on_process,
};
-static void do_quit(void *userdata, int signal_number)
+static void do_quit(void* userdata, int signal_number)
{
- struct data *data = userdata;
- pw_main_loop_quit(data->loop);
+ struct data* data = userdata;
+ pw_main_loop_quit(data->loop);
}
-int main(int argc, char *argv[])
+int main(int argc, char* argv[])
{
- struct data data = { 0, };
+ struct data data = {
+ 0,
+ };
- delay_init( &data.delay );
+ gate_init(&data.fx_data.gate);
+ delay_init(&data.fx_data.delay);
+ sust_init(&data.fx_data.sust);
+ data.fx_data.prog = 0;
- const struct spa_pod *params[1];
- uint8_t buffer[1024];
- struct spa_pod_builder b = SPA_POD_BUILDER_INIT(buffer, sizeof(buffer));
+ const struct spa_pod* params[1];
+ uint8_t buffer[1024];
+ struct spa_pod_builder b = SPA_POD_BUILDER_INIT(buffer, sizeof(buffer));
- pw_init(&argc, &argv);
+ pw_init(&argc, &argv);
- data.loop = pw_main_loop_new(NULL);
+ data.loop = pw_main_loop_new(NULL);
- pw_loop_add_signal(pw_main_loop_get_loop(data.loop), SIGINT, do_quit, &data);
- pw_loop_add_signal(pw_main_loop_get_loop(data.loop), SIGTERM, do_quit, &data);
+ pw_loop_add_signal(pw_main_loop_get_loop(data.loop), SIGINT, do_quit, &data);
+ pw_loop_add_signal(pw_main_loop_get_loop(data.loop), SIGTERM, do_quit, &data);
- data.filter = pw_filter_new_simple(
- pw_main_loop_get_loop(data.loop),
- "Guitar FX",
- pw_properties_new(
- PW_KEY_MEDIA_TYPE, "Audio",
- PW_KEY_MEDIA_CATEGORY, "Filter",
- PW_KEY_MEDIA_ROLE, "DSP",
- NULL),
- &filter_events,
- &data);
+ data.filter = pw_filter_new_simple(
+ pw_main_loop_get_loop(data.loop), "Guitar FX",
+ pw_properties_new(PW_KEY_MEDIA_TYPE, "Audio", PW_KEY_MEDIA_CATEGORY,
+ "Filter", PW_KEY_MEDIA_ROLE, "DSP", NULL),
+ &filter_events, &data);
- data.midi_in_port = pw_filter_add_port(data.filter,
- PW_DIRECTION_INPUT,
- PW_FILTER_PORT_FLAG_MAP_BUFFERS,
- sizeof(struct port),
- pw_properties_new(
- PW_KEY_FORMAT_DSP, "8 bit raw midi",
- PW_KEY_PORT_NAME, "midi in",
- NULL
- ),
- NULL, 0
- );
+ data.midi_in_port = pw_filter_add_port(data.filter, PW_DIRECTION_INPUT,
+ PW_FILTER_PORT_FLAG_MAP_BUFFERS, sizeof(struct port),
+ pw_properties_new(PW_KEY_FORMAT_DSP, "8 bit raw midi",
+ PW_KEY_PORT_NAME, "midi in", NULL),
+ NULL, 0);
- data.guit_in_port = pw_filter_add_port(data.filter,
- PW_DIRECTION_INPUT,
- PW_FILTER_PORT_FLAG_MAP_BUFFERS,
- sizeof(struct port),
- pw_properties_new(
- PW_KEY_FORMAT_DSP, "32 bit float mono audio",
- PW_KEY_PORT_NAME, "guitar in",
- NULL),
- NULL, 0);
+ data.guit_in_port = pw_filter_add_port(
+ data.filter, PW_DIRECTION_INPUT, PW_FILTER_PORT_FLAG_MAP_BUFFERS,
+ sizeof(struct port),
+ pw_properties_new(PW_KEY_FORMAT_DSP, "32 bit float mono audio",
+ PW_KEY_PORT_NAME, "guitar in", NULL),
+ NULL, 0);
- data.out_port = pw_filter_add_port(data.filter,
- PW_DIRECTION_OUTPUT,
- PW_FILTER_PORT_FLAG_MAP_BUFFERS,
- sizeof(struct port),
- pw_properties_new(
- PW_KEY_FORMAT_DSP, "32 bit float mono audio",
- PW_KEY_PORT_NAME, "fx out",
- NULL),
- NULL, 0);
+ data.out_port = pw_filter_add_port(
+ data.filter, PW_DIRECTION_OUTPUT, PW_FILTER_PORT_FLAG_MAP_BUFFERS,
+ sizeof(struct port),
+ pw_properties_new(PW_KEY_FORMAT_DSP, "32 bit float mono audio",
+ PW_KEY_PORT_NAME, "fx out", NULL),
+ NULL, 0);
- params[0] = spa_process_latency_build(&b,
- SPA_PARAM_ProcessLatency,
- &SPA_PROCESS_LATENCY_INFO_INIT(
- .ns = 10 * SPA_NSEC_PER_MSEC
- ));
+ params[0] = spa_process_latency_build(
+ &b, SPA_PARAM_ProcessLatency,
+ &SPA_PROCESS_LATENCY_INFO_INIT(.ns = 10 * SPA_NSEC_PER_MSEC));
- if (pw_filter_connect(data.filter,
- PW_FILTER_FLAG_RT_PROCESS,
- params, 1) < 0) {
- fprintf(stderr, "can't connect\n");
- return -1;
- }
+ if (pw_filter_connect(data.filter, PW_FILTER_FLAG_RT_PROCESS, params, 1) < 0) {
+ fprintf(stderr, "can't connect\n");
+ return -1;
+ }
- pw_main_loop_run(data.loop);
+ pw_main_loop_run(data.loop);
- pw_filter_destroy(data.filter);
- pw_main_loop_destroy(data.loop);
- pw_deinit();
+ pw_filter_destroy(data.filter);
+ pw_main_loop_destroy(data.loop);
+ pw_deinit();
- return 0;
+ return 0;
}
diff --git a/guitfx.h b/guitfx.h
new file mode 100644
index 0000000..4dedcdd
--- /dev/null
+++ b/guitfx.h
@@ -0,0 +1,16 @@
+
+#include "delay.h"
+#include "sust.h"
+#include "gate.h"
+
+struct FxData {
+ uint64_t last_tap;
+ struct delay delay;
+ struct sust sust;
+ struct gate gate;
+
+ unsigned prog;
+
+ //! elapsed time in number of samples
+ uint64_t time;
+};
diff --git a/meson.build b/meson.build
index 5f61c36..ab53a04 100644
--- a/meson.build
+++ b/meson.build
@@ -1,8 +1,15 @@
project('guitfx', 'c')
pipewire_dep = dependency('libpipewire-0.3')
+
+cc = meson.get_compiler('c')
+m_dep = cc.find_library('m', required : false)
+
executable(
'guitfx',
'guitfx.c',
'delay.c',
- dependencies : [pipewire_dep],
+ 'sust.c',
+ 'gate.c',
+ 'controller.c',
+ dependencies : [pipewire_dep, m_dep],
)
diff --git a/sust.c b/sust.c
new file mode 100644
index 0000000..f9d31a2
--- /dev/null
+++ b/sust.c
@@ -0,0 +1,91 @@
+#include "sust.h"
+#include <math.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+void sust_init(struct sust* sust)
+{
+ sust->mode = MODE_Sostenuto;
+
+ sust->playing = false;
+
+ sust->start_idx = 0;
+ sust->idx = 0;
+
+ sust->buf_len = 51200;
+ sust->record_buf = malloc(sizeof(float) * sust->buf_len);
+ sust->play_buf = malloc(sizeof(float) * sust->buf_len);
+}
+
+float envelope(float x)
+{
+ if (x < 0.4)
+ return (x / 0.4) * (x / 0.4);
+ if (x < 0.6)
+ return 1.0;
+
+ float v = 1.0 - ((x - 0.6) / 0.4);
+ return v * v;
+}
+
+float softcos(float x)
+{
+ return sin(x * (3.141 / 2.0));
+}
+
+void sust_resize(struct sust* sust, size_t new_len)
+{
+ sust->buf_len = new_len;
+ sust->play_buf = realloc(sust->play_buf, sizeof(float) * new_len);
+ sust->record_buf = realloc(sust->record_buf, sizeof(float) * new_len);
+ sust->idx %= new_len;
+}
+
+void sust_swap(
+ struct sust* sust)
+{
+ float* tmp = sust->play_buf;
+ sust->play_buf = sust->record_buf;
+ sust->record_buf = tmp;
+
+ for (int i = 0; i < sust->buf_len; ++i) {
+ sust->record_buf[i] = sust->play_buf[i];
+ }
+}
+
+void sust_process(
+ struct sust* sust,
+ size_t frame_size,
+ float const* in,
+ float* out)
+{
+ for (size_t i = 0; i < frame_size; ++i) {
+
+ if (sust->mode == MODE_Sustain && sust->idx == 0) {
+ sust_swap(sust);
+ }
+
+ float out_value = in[i];
+
+ if (sust->playing) {
+ int n_voices = 5;
+
+ for (int v = 0; v < n_voices; ++v) {
+ size_t play_idx = (sust->start_idx + sust->idx + ((v * sust->buf_len) / n_voices)) % sust->buf_len;
+ float gain = envelope(((float)play_idx) / ((float)sust->buf_len));
+ // printf("gain = %f\n", gain);
+ out_value += 0.5 * gain * sust->play_buf[play_idx];
+ }
+ }
+
+ if (sust->mode == MODE_Sostenuto) {
+ sust->record_buf[sust->idx] = in[i];
+ }
+ if (sust->mode == MODE_Sustain) {
+ sust->record_buf[sust->idx] = 0.5 * out_value;
+ }
+
+ sust->idx = (sust->idx + 1) % sust->buf_len;
+ out[i] = out_value;
+ }
+}
diff --git a/sust.h b/sust.h
new file mode 100644
index 0000000..a0472b1
--- /dev/null
+++ b/sust.h
@@ -0,0 +1,30 @@
+#pragma once
+
+#include <stdbool.h>
+#include <stddef.h>
+
+enum sust_mode {
+ MODE_Sustain = 0,
+ MODE_Sostenuto = 1
+};
+
+struct sust {
+ enum sust_mode mode;
+ bool playing;
+
+ size_t start_idx;
+ size_t idx;
+ size_t buf_len;
+ float* record_buf;
+ float* play_buf;
+};
+
+void sust_init(struct sust* sust);
+void sust_resize(struct sust* sust, size_t new_len);
+void sust_swap(struct sust* sust);
+
+void sust_process(
+ struct sust* sust,
+ size_t frame_size,
+ float const* in,
+ float* out);