audio-src.c

Audio source using pw_stream.

/* PipeWire */
/* SPDX-FileCopyrightText: Copyright © 2018 Wim Taymans */
/* SPDX-License-Identifier: MIT */
 
/*
 [title]
 Audio source using \ref pw_stream "pw_stream".
 [title]
 */
 
#include <stdio.h>
#include <errno.h>
#include <math.h>
#include <signal.h>
 
#include <spa/param/audio/format-utils.h>
 
#include <pipewire/pipewire.h>
 
#define M_PI_M2 ( M_PI + M_PI )
 
#define DEFAULT_RATE            44100
#define DEFAULT_CHANNELS        2
#define DEFAULT_VOLUME          0.7
 
struct data {
        struct pw_main_loop *loop;
        struct pw_stream *stream;
 
        double accumulator;
};
 
static void fill_f32(struct data *d, void *dest, int n_frames)
{
        float *dst = dest, val;
        int i, c;
 
        for (i = 0; i < n_frames; i++) {
                d->accumulator += M_PI_M2 * 440 / DEFAULT_RATE;
                if (d->accumulator >= M_PI_M2)
                        d->accumulator -= M_PI_M2;
 
                val = sin(d->accumulator) * DEFAULT_VOLUME;
                for (c = 0; c < DEFAULT_CHANNELS; c++)
                        *dst++ = val;
        }
}
 
/* our data processing function is in general:
 *
 *  struct pw_buffer *b;
 *  b = pw_stream_dequeue_buffer(stream);
 *
 *  .. generate stuff in the buffer ...
 *
 *  pw_stream_queue_buffer(stream, b);
 */
static void on_process(void *userdata)
{
        struct data *data = userdata;
        struct pw_buffer *b;
        struct spa_buffer *buf;
        int n_frames, stride;
        uint8_t *p;
 
        if ((b = pw_stream_dequeue_buffer(data->stream)) == NULL) {
                pw_log_warn("out of buffers: %m");
                return;
        }
 
        buf = b->buffer;
        if ((p = buf->datas[0].data) == NULL)
                return;
 
        stride = sizeof(float) * DEFAULT_CHANNELS;
        n_frames = SPA_MIN(b->requested, buf->datas[0].maxsize / stride);
 
        fill_f32(data, p, n_frames);
 
        buf->datas[0].chunk->offset = 0;
        buf->datas[0].chunk->stride = stride;
        buf->datas[0].chunk->size = n_frames * stride;
 
        pw_stream_queue_buffer(data->stream, b);
}
 
static const struct pw_stream_events stream_events = {
        PW_VERSION_STREAM_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, };
        const struct spa_pod *params[1];
        uint8_t buffer[1024];
        struct pw_properties *props;
        struct spa_pod_builder b = SPA_POD_BUILDER_INIT(buffer, sizeof(buffer));
 
        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 stream, the simple stream manages the core and remote
         * objects for you if you don't need to deal with them.
         *
         * If you plan to autoconnect your stream, you need to provide at least
         * media, category and role properties.
         *
         * Pass your events and a user_data pointer as the last arguments. This
         * will inform you about the stream state. The most important event
         * you need to listen to is the process event where you need to produce
         * the data.
         */
        props = pw_properties_new(PW_KEY_MEDIA_TYPE, "Audio",
                        PW_KEY_MEDIA_CATEGORY, "Playback",
                        PW_KEY_MEDIA_ROLE, "Music",
                        NULL);
        if (argc > 1)
                /* Set stream target if given on command line */
                pw_properties_set(props, PW_KEY_TARGET_OBJECT, argv[1]);
        data.stream = pw_stream_new_simple(
                        pw_main_loop_get_loop(data.loop),
                        "audio-src",
                        props,
                        &stream_events,
                        &data);
 
        /* Make one parameter with the supported formats. The SPA_PARAM_EnumFormat
         * id means that this is a format enumeration (of 1 value). */
        params[0] = spa_format_audio_raw_build(&b, SPA_PARAM_EnumFormat,
                        &SPA_AUDIO_INFO_RAW_INIT(
                                .format = SPA_AUDIO_FORMAT_F32,
                                .channels = DEFAULT_CHANNELS,
                                .rate = DEFAULT_RATE ));
 
        /* Now connect this stream. We ask that our process function is
         * called in a realtime thread. */
        pw_stream_connect(data.stream,
                          PW_DIRECTION_OUTPUT,
                          PW_ID_ANY,
                          PW_STREAM_FLAG_AUTOCONNECT |
                          PW_STREAM_FLAG_MAP_BUFFERS |
                          PW_STREAM_FLAG_RT_PROCESS,
                          params, 1);
 
        /* and wait while we let things run */
        pw_main_loop_run(data.loop);
 
        pw_stream_destroy(data.stream);
        pw_main_loop_destroy(data.loop);
        pw_deinit();
 
        return 0;
}