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#include <alsa/asoundlib.h>
#include <alsa/seq.h>
#include <sys/time.h>
#include <sched.h>
void
callback(snd_seq_t *handle)
{
snd_seq_event_t *ev = 0;
do {
if (snd_seq_event_input(handle, &ev) > 0) {
if (ev->type == SND_SEQ_EVENT_NOTEON) {
struct timeval tv;
static long last_usec = 0;
int pitch = ev->data.note.note;
snd_seq_timestamp_t evt = ev->time;
gettimeofday(&tv, 0);
printf("pitch %d at %ld sec %ld usec, off by %ld usec\n",
pitch, tv.tv_sec, tv.tv_usec, tv.tv_usec - ((last_usec + 500000) % 1000000));
last_usec = tv.tv_usec;
}
}
} while (snd_seq_event_input_pending(handle, 0) > 0);
}
int
main(int argc, char **argv)
{
snd_seq_t *handle;
int portid;
int npfd;
struct pollfd *pfd;
struct sched_param param;
if (snd_seq_open(&handle, "hw", SND_SEQ_OPEN_DUPLEX, 0) < 0) {
fprintf(stderr, "failed to open ALSA sequencer interface\n");
return 1;
}
snd_seq_set_client_name(handle, "complainer");
if ((portid = snd_seq_create_simple_port
(handle, "complainer",
SND_SEQ_PORT_CAP_WRITE | SND_SEQ_PORT_CAP_SUBS_WRITE, 0)) < 0) {
fprintf(stderr, "failed to create ALSA sequencer port\n");
return 1;
}
npfd = snd_seq_poll_descriptors_count(handle, POLLIN);
pfd = (struct pollfd *)alloca(npfd * sizeof(struct pollfd));
snd_seq_poll_descriptors(handle, pfd, npfd, POLLIN);
param.sched_priority = 99;
if (sched_setscheduler(0, SCHED_FIFO, ¶m)) {
perror("failed to set high-priority scheduler");
}
printf("ready\n", npfd);
while (1) {
if (poll(pfd, npfd, 100000) > 0) {
callback(handle);
}
}
}
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