audio-dsp-sink.c

Audio sink using pw_filter

Audio sink using pw_filter

/* PipeWire */
/* SPDX-FileCopyrightText: Copyright © 2025 Wim Taymans */
/* SPDX-License-Identifier: MIT */
 
/*
 [title]
 Audio sink using \ref pw_filter "pw_filter"
 [title]
 */
 
#include "config.h"
 
#include <stdio.h>
#include <errno.h>
#include <math.h>
#include <signal.h>
#include <fcntl.h>
#include <sys/mman.h>
 
#include <pipewire/pipewire.h>
#include <pipewire/filter.h>
 
/* define to make this filter allocate buffer memory */
#define ALLOC_BUFFERS
 
struct data;
 
struct port {
        struct data *data;
};
 
struct data {
        struct pw_main_loop *loop;
        struct pw_filter *filter;
        struct port *in_port;
        bool move;
        uint32_t quantum_limit;
};
 
/* our data processing function is in general:
 *
 *  struct pw_buffer *b;
 *  out = pw_filter_dequeue_buffer(filter, in_port);
 *
 *  .. consume data in the buffer ...
 *
 *  pw_filter_queue_buffer(filter, in_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 *in, max;
        struct port *in_port = data->in_port;
        uint32_t i, n_samples = position->clock.duration, peak;
 
        pw_log_trace("do process %d", n_samples);
 
        in = pw_filter_get_dsp_buffer(in_port, n_samples);
        if (in == NULL)
                return;
 
        /* move cursor up */
        if (data->move)
                fprintf(stdout, "%c[%dA", 0x1b, 2);
        fprintf(stdout, "captured %d samples\n", n_samples);
        max = 0.0f;
        for (i = 0; i < n_samples; i++)
                max = fmaxf(max, fabsf(in[i]));
 
        peak = (uint32_t)SPA_CLAMPF(max * 30, 0.f, 39.f);
 
        fprintf(stdout, "input: |%*s%*s| peak:%f\n", peak+1, "*", 40 - peak, "", max);
        data->move = true;
        fflush(stdout);
}
 
#ifdef ALLOC_BUFFERS
/* close the memfd we set on the buffers here */
static void on_remove_buffer(void *_data, void *_port_data, struct pw_buffer *buffer)
{
        struct spa_buffer *buf = buffer->buffer;
        struct spa_data *d;
 
        d = buf->datas;
        pw_log_info("remove buffer %p", buffer);
 
        close(d[0].fd);
}
 
/* we set the PW_STREAM_FLAG_ALLOC_BUFFERS flag when connecting so we need
 * to provide buffer memory.  */
static void on_add_buffer(void *_data, void *_port_data, struct pw_buffer *buffer)
{
        struct data *data = _data;
        struct spa_buffer *buf = buffer->buffer;
        struct spa_data *d;
 
        pw_log_info("add buffer %p", buffer);
        d = buf->datas;
 
        if ((d[0].type & (1<<SPA_DATA_MemFd)) == 0) {
                pw_log_error("unsupported data type %08x", d[0].type);
                return;
        }
 
        /* create the memfd on the buffer, set the type and flags */
        d[0].type = SPA_DATA_MemFd;
        d[0].flags = SPA_DATA_FLAG_READWRITE | SPA_DATA_FLAG_MAPPABLE;
#ifdef HAVE_MEMFD_CREATE
        d[0].fd = memfd_create("audio-dsp-sink-memfd", MFD_CLOEXEC);
#else
        d[0].fd = -1;
#endif
        if (d[0].fd == -1) {
                pw_log_error("can't create memfd: %m");
                return;
        }
        d[0].mapoffset = 0;
        d[0].maxsize = data->quantum_limit * sizeof(float);
 
        /* truncate to the right size */
        if (ftruncate(d[0].fd, d[0].maxsize) < 0) {
                pw_log_error("can't truncate to %d: %m", d[0].maxsize);
                return;
        }
}
#endif
 
static const struct pw_filter_events filter_events = {
        PW_VERSION_FILTER_EVENTS,
        .process = on_process,
#ifdef ALLOC_BUFFERS
        .add_buffer = on_add_buffer,
        .remove_buffer = on_remove_buffer,
#endif
};
 
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, };
        uint32_t flags;
 
        pw_init(&argc, &argv);
 
        data.quantum_limit= 8192;
 
        /* 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-sink",
                        pw_properties_new(
                                PW_KEY_MEDIA_TYPE, "Audio",
                                PW_KEY_MEDIA_CATEGORY, "Sink",
                                PW_KEY_MEDIA_ROLE, "DSP",
                                PW_KEY_MEDIA_CLASS, "Stream/Input/Audio",
                                PW_KEY_NODE_AUTOCONNECT, "true",
                                NULL),
                        &filter_events,
                        &data);
 
        flags = PW_FILTER_PORT_FLAG_MAP_BUFFERS;
#ifdef ALLOC_BUFFERS
        flags |= PW_FILTER_PORT_FLAG_ALLOC_BUFFERS;
#endif
 
        /* make an audio DSP output port */
        data.in_port = pw_filter_add_port(data.filter,
                        PW_DIRECTION_INPUT,
                        flags,
                        sizeof(struct port),
                        pw_properties_new(
                                PW_KEY_FORMAT_DSP, "32 bit float mono audio",
                                PW_KEY_PORT_NAME, "input",
                                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;
}