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Copyright (C) 4Front Technologies, 2002-2004. Released under GPLv2/CDDL.
This program opens an audio device and then just copies input to output. Select is used for flow control.
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/time.h>
#include <sys/types.h>
#include <fcntl.h>
#include <soundcard.h>
#ifdef _AIX
#include <sys/select.h>
#endif
int
main (int agrc, char *argv[])
{
int fd;
int tmp;
char buf[128 * 1024];
int have_data = 0;
int n, l;
int frag = 0x00200008; /* 32 fragments of 2^8=256 bytes */
fd_set reads, writes;
close (0);
if ((fd = open ("/dev/dsp", O_RDWR, 0)) == -1)
{
perror ("/dev/dsp open");
exit (-1);
}
ioctl (fd, SNDCTL_DSP_SETFRAGMENT, &frag);
Set just the sampling tahe. Use the default format. We do not do any error checking (maybe not so good idea) because we don't care what the sampling rate really is.
tmp = 48000;
ioctl (fd, SNDCTL_DSP_SPEED, &tmp);
while (1)
{
struct timeval time;
FD_ZERO (&reads);
FD_ZERO (&writes);
if (have_data)
FD_SET (fd, &writes);
else
FD_SET (fd, &reads);
time.tv_sec = 1;
time.tv_usec = 0;
if (select (fd + 1, &reads, &writes, NULL, &time) == -1)
{
perror ("select");
exit (-1);
}
if (FD_ISSET (fd, &reads))
{
struct audio_buf_info info;
if (ioctl (fd, SNDCTL_DSP_GETISPACE, &info) == -1)
{
perror ("select");
exit (-1);
}
n = info.bytes;
l = read (fd, buf, n);
if (l > 0)
have_data = 1;
}
if (FD_ISSET (fd, &writes))
{
int i;
struct audio_buf_info info;
if (ioctl (fd, SNDCTL_DSP_GETOSPACE, &info) == -1)
{
perror ("select");
exit (-1);
}
n = info.bytes;
printf ("Write %d\n", l);
write (fd, buf, l);
printf ("OK");
have_data = 0;
}
}
exit (0);
}