audio-dsp-src.c

Audio source using pw_filter

Audio source using pw_filter

/* 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_M2f (float)(M_PI+M_PI)
 
#define DEFAULT_RATE            44100
#define DEFAULT_FREQ            440
#define DEFAULT_VOLUME          0.7f
 
struct data;
 
struct port {
        struct data *data;
        float 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_M2f * DEFAULT_FREQ / DEFAULT_RATE;
                if (out_port->accumulator >= M_PI_M2f)
                        out_port->accumulator -= M_PI_M2f;
 
                *out++ = sinf(out_port->accumulator) * DEFAULT_VOLUME;
        }
}
 
static const struct pw_filter_events filter_events = {
        PW_VERSION_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(
                        pw_main_loop_get_loop(data.loop),
                        "audio-dsp-src",
                        pw_properties_new(
                                PW_KEY_MEDIA_TYPE, "Audio",
                                PW_KEY_MEDIA_CATEGORY, "Source",
                                PW_KEY_MEDIA_ROLE, "DSP",
                                PW_KEY_MEDIA_CLASS, "Stream/Output/Audio",
                                PW_KEY_NODE_AUTOCONNECT, "true",
                                NULL),
                        &filter_events,
                        &data);
 
        /* make an audio DSP output port */
        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, "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,
                                PW_FILTER_FLAG_RT_PROCESS,
                                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);
        pw_main_loop_destroy(data.loop);
        pw_deinit();
 
        return 0;
}