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Copyright (C) 4Front Technologies, 2002-2004. Released under GPLv2/CDDL.
This program plays a frequency seep up starting from 10 Hz and goes up to sample_rate/2.
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <soundcard.h>
char *dspname = "/dev/dsp";
int fd;
int
main (int argc, char *argv[])
{
int bits, channels, speed, tmp;
int i, l, n;
#define BUFFSIZE (64*1024)
short buf[BUFFSIZE];
int p, t;
double freq = 10.0 /* Hz */ , phase = 0.0;
int delay = 0;
if (argc > 1)
dspname = argv[1];
if (argc > 2)
delay = atoi (argv[2]);
if ((fd = open (dspname, O_WRONLY, 0)) == -1)
{
perror (dspname);
exit (-1);
}
speed = 48000;
channels = 2;
bits = AFMT_S16_NE;
if (ioctl (fd, SNDCTL_DSP_CHANNELS, &channels) == -1)
{
perror ("SNDCTL_DSP_CHANNELS");
exit (-1);
}
if (ioctl (fd, SNDCTL_DSP_SETFMT, &bits) == -1)
{
perror ("SNDCTL_DSP_SETFMT");
exit (-1);
}
if (bits != AFMT_S16_NE)
{
fprintf (stderr,
"Device %s doesn't support 16 bit (native endian) format\n",
dspname);
exit (-1);
}
if (ioctl (fd, SNDCTL_DSP_SPEED, &speed) == -1)
{
perror ("SNDCTL_DSP_SPEED");
exit (-1);
}
fprintf (stderr, "Outputting sweep at %d Hz, %d channels, 16 bits\n", speed,
channels);
n = 0;
p = 0;
while (1) /* Infinite loop */
{
int v;
double step;
v = sin (phase) * 16483.0;
for (i = 0; i < channels; i++)
{
buf[p++] = v;
if (p >= BUFFSIZE)
{
// write (1, buf, p * 2);
if (write (fd, buf, p * 2) != p * 2)
{
perror ("write");
exit (-1);
}
if (delay > 0)
usleep (delay * 1000);
fprintf (stderr, "\r%d ", (int) (freq));
fflush (stderr);
p = 0;
}
}
step = 2.0 * M_PI * freq / (double) speed;
phase += step;
if (freq < (double) speed / 2.1)
freq *= 1.000002;
else
break;
}
fprintf (stderr, "\n");
if (p > 0)
write (fd, buf, p * 2);
exit (0);
}