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111 lines
2.2 KiB
C
111 lines
2.2 KiB
C
/*
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* midigen.c - MIDI traffic generator
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*
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* Written 2011 by Werner Almesberger
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* Copyright 2011 Werner Almesberger
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*/
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#include <stdlib.h>
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#include <stdio.h>
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#include <unistd.h>
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#include <sys/time.h>
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#include <alsa/asoundlib.h>
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#define NAME "midigen"
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static void send_cc(snd_seq_t *midi, snd_seq_event_t *ev, int chan)
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{
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static unsigned v = 0;
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snd_seq_ev_set_controller(ev, chan, (v >> 7) & 127, v & 127);
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v++;
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snd_seq_event_output(midi, ev);
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snd_seq_drain_output(midi);
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}
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static void generate(snd_seq_t *midi, int port, int chan, int t_s, int t_us)
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{
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snd_seq_event_t ev;
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struct timeval next, now;
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int dt_us;
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snd_seq_ev_clear(&ev);
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snd_seq_ev_set_source(&ev, port);
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snd_seq_ev_set_subs(&ev);
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snd_seq_ev_set_direct(&ev);
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gettimeofday(&next, NULL);
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while (1) {
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next.tv_sec += t_s;
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next.tv_usec += t_us;
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if (next.tv_usec > 999999) {
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next.tv_sec++;
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next.tv_usec -= 1000000;
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}
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gettimeofday(&now, NULL);
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dt_us = (next.tv_sec-now.tv_sec)*1000000+
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next.tv_usec-now.tv_usec;
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if (dt_us > 0)
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usleep(dt_us);
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send_cc(midi, &ev, chan);
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}
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}
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static void usage(const char *name)
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{
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fprintf(stderr, "usage: %s [-c channel] rate_hz\n", name);
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exit(1);
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}
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int main(int argc, char **argv)
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{
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snd_seq_t *midi;
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int c;
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int chan = 0, t_us;
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int port;
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while ((c = getopt(argc, argv, "c:")) != EOF)
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switch (c) {
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case 'c':
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chan = atoi(optarg);
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break;
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default:
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usage(*argv);
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}
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switch (argc-optind) {
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case 1:
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t_us = 1000000/atof(argv[optind]);
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break;
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default:
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usage(*argv);
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}
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if (snd_seq_open(&midi, "hw", SND_SEQ_OPEN_OUTPUT,0) < 0) {
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fprintf(stderr, "can't open ALSA sequencer\n");
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exit(1);
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}
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snd_seq_set_client_name(midi, NAME);
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port = snd_seq_create_simple_port(midi, NAME,
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SND_SEQ_PORT_CAP_READ | SND_SEQ_PORT_CAP_SUBS_READ,
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SND_SEQ_PORT_TYPE_APPLICATION);
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if (port < 0) {
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fprintf(stderr, "can't create sequencer port\n");
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exit(1);
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}
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generate(midi, port, chan, t_us/1000000, t_us % 1000000);
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return 0;
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}
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