PipeWire  1.0.7
audio-dsp-src.c

doc} audio-dsp-src.c title
doc} audio-dsp-src.c doc

/* PipeWire */
/* SPDX-FileCopyrightText: Copyright © 2020 Wim Taymans */
/* SPDX-License-Identifier: MIT */
/*
[title]
Audio source using \ref pw_filter "pw_filter"
[title]
*/
#include <stdio.h>
#include <errno.h>
#include <math.h>
#include <signal.h>
#include <pipewire/pipewire.h>
#include <pipewire/filter.h>
#define M_PI_M2 ( M_PI + M_PI )
#define DEFAULT_RATE 44100
#define DEFAULT_FREQ 440
#define DEFAULT_VOLUME 0.7
struct data;
struct port {
struct data *data;
double accumulator;
};
struct data {
struct pw_main_loop *loop;
struct pw_filter *filter;
struct port *out_port;
};
/* our data processing function is in general:
*
* struct pw_buffer *b;
* out = pw_filter_dequeue_buffer(filter, out_port);
*
* .. generate data in the buffer ...
*
* pw_filter_queue_buffer(filter, out_port, out);
*
* For DSP ports, there is a shortcut to directly dequeue, get
* the data and requeue the buffer with pw_filter_get_dsp_buffer().
*/
static void on_process(void *userdata, struct spa_io_position *position)
{
struct data *data = userdata;
float *out;
struct port *out_port = data->out_port;
uint32_t i, n_samples = position->clock.duration;
pw_log_trace("do process %d", n_samples);
out = pw_filter_get_dsp_buffer(out_port, n_samples);
if (out == NULL)
return;
for (i = 0; i < n_samples; i++) {
out_port->accumulator += M_PI_M2 * DEFAULT_FREQ / DEFAULT_RATE;
if (out_port->accumulator >= M_PI_M2)
out_port->accumulator -= M_PI_M2;
*out++ = sin(out_port->accumulator) * DEFAULT_VOLUME;
}
}
static const struct pw_filter_events filter_events = {
.process = on_process,
};
static void do_quit(void *userdata, int signal_number)
{
struct data *data = userdata;
pw_main_loop_quit(data->loop);
}
int main(int argc, char *argv[])
{
struct data data = { 0, };
pw_init(&argc, &argv);
/* make a main loop. If you already have another main loop, you can add
* the fd of this pipewire mainloop to it. */
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);
/* Create a simple filter, the simple filter manages the core and remote
* objects for you if you don't need to deal with them.
*
* Pass your events and a user_data pointer as the last arguments. This
* will inform you about the filter state. The most important event
* you need to listen to is the process event where you need to process
* the data.
*/
data.filter = pw_filter_new_simple(
"audio-dsp-src",
PW_KEY_MEDIA_CLASS, "Stream/Output/Audio",
NULL),
&filter_events,
&data);
/* make an audio DSP output port */
data.out_port = pw_filter_add_port(data.filter,
sizeof(struct port),
PW_KEY_FORMAT_DSP, "32 bit float mono audio",
PW_KEY_PORT_NAME, "output",
NULL),
NULL, 0);
/* Now connect this filter. We ask that our process function is
* called in a realtime thread. */
if (pw_filter_connect(data.filter,
NULL, 0) < 0) {
fprintf(stderr, "can't connect\n");
return -1;
}
/* and wait while we let things run */
pw_main_loop_run(data.loop);
pw_filter_destroy(data.filter);
return 0;
}