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/*
* Purpose: Measuring the hardware level latencies.
* Copyright (C) 4Front Technologies, 2002-2004. Released under GPLv2/CDDL.
*
* Description:
* This simple program was once used to measure internal latencies of some
* sound cards. It was written in great hurry so don't use it as a program
* template. Error checking is completely inadequate.
*
* This program requires that the output of the sound card is connected
* to the line in of the same card.
*
* The program will play a short spike and then measure how many "silent "
* samples there are in the input before the spike is seen. You can
* get the delay in seconds by dividing this sample count by the
* sample rate.
*
* This is the total delay value that includes both the output and input
* delays. There is no way to estimate how large part of it is caused by
* input or output.
*/
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <sys/time.h>
#include <sys/types.h>
#include <fcntl.h>
#include <soundcard.h>
#ifdef _AIX
#include <sys/select.h>
#endif
int frag_size = 0;
static int pos = 0;
static int
open_device (char *name, int mode)
{
int tmp, fd;
int frag = 0x0020000b; /* 32 fragments of 2^11=2048 bytes */
if ((fd = open (name, mode, 0)) == -1)
{
perror (name);
exit (-1);
}
/*
* WARNING!!!!!!!!!!!
*
* The following code makes ioctl calls without verifying that the
* result was OK. Don't do this at home.
*/
if (ioctl (fd, SNDCTL_DSP_SETFRAGMENT, &frag) == -1)
perror ("SNDCTL_DSP_SETFRAGMENT");
tmp = 1;
if (ioctl (fd, SNDCTL_DSP_CHANNELS, &tmp) == -1)
perror ("SNDCTL_DSP_CHANNELS");
tmp = AFMT_S16_NE;
if (ioctl (fd, SNDCTL_DSP_SETFMT, &tmp) == -1)
perror ("SNDCTL_DSP_SETFMT");
tmp = 48000;
if (ioctl (fd, SNDCTL_DSP_SPEED, &tmp) == -1) /* And #channels & #bits if required */
perror ("SNDCTL_DSP_SPEED");
if (ioctl (fd, SNDCTL_DSP_GETBLKSIZE, &frag_size) == -1)
perror ("SNDCTL_DSP_GETBLKSIZE");
tmp = 0;
if (ioctl (fd, SNDCTL_DSP_SETTRIGGER, &tmp) == -1)
perror ("SNDCTL_DSP_SETTRIGGER");
/*
* WARNING!!!!!!!!!!!
*
* The above code makes ioctl calls without verifying that the
* result was OK. Don't do this at home.
*/
return fd;
}
static void
gen_spike (short *buf)
{
int i, p;
for (i = 0; i < 30; i++)
{
p = (i / 4) % 3;
buf[i] = (p - 1) * 8 * 1024;
}
}
static void
check_buf (short *buf, int l)
{
int i;
for (i = 0; i < l; i++)
{
int v;
v = buf[i];
if (v < 0)
v = -v;
if (v > 4096)
printf ("%d = %d\n", pos, v);
pos++;
}
}
int
main (int argc, char *argv[])
{
int fd_in, fd_out;
char *name_in = "/dev/dsp", *name_out = NULL;
int tmp;
int have_data = 0;
char buf[128 * 1024];
int n, l;
fd_set reads, writes;
if (argc > 1)
name_in = argv[1];
if (argc > 2)
name_out = argv[2];
if (name_out != NULL)
{
fd_in = open_device (name_in, O_RDONLY);
fd_out = open_device (name_out, O_WRONLY);
}
else
{
fd_in = fd_out == open_device (name_in, O_RDWR);
}
memset (buf, 0, frag_size);
gen_spike ((short *) buf);
write (fd_out, buf, frag_size);
if (fd_out != fd_in)
{
tmp = PCM_ENABLE_INPUT;
ioctl (fd_in, SNDCTL_DSP_SETTRIGGER, &tmp);
tmp = PCM_ENABLE_OUTPUT;
ioctl (fd_out, SNDCTL_DSP_SETTRIGGER, &tmp);
}
else
{
tmp = PCM_ENABLE_INPUT | PCM_ENABLE_OUTPUT;
ioctl (fd_in, SNDCTL_DSP_SETTRIGGER, &tmp);
}
while (1)
{
struct timeval time;
FD_ZERO (&reads);
FD_ZERO (&writes);
FD_SET (fd_out, &writes);
FD_SET (fd_in, &reads);
time.tv_sec = 0;
time.tv_usec = 100000;
if ((l = select (fd_out + 1, &reads, &writes, NULL, &time)) == -1)
{
perror ("select");
exit (-1);
}
if (l == 0)
printf ("Timeout ");
if (FD_ISSET (fd_in, &reads))
{
struct audio_buf_info info;
if (ioctl (fd_in, SNDCTL_DSP_GETISPACE, &info) == -1)
{
perror ("select");
exit (-1);
}
n = info.bytes;
if (n <= 0)
{
printf ("Error: NREAD=%d\n", n);
exit (-1);
}
l = read (fd_in, buf, n);
if (l > 0)
have_data = 1;
else
perror ("read");
check_buf ((short *) buf, l / 2);
}
if (FD_ISSET (fd_out, &writes))
{
int i;
struct audio_buf_info info;
if (ioctl (fd_out, SNDCTL_DSP_GETOSPACE, &info) == -1)
{
perror ("select");
exit (-1);
}
n = info.bytes;
/* printf("Write %d", l); */
l = n;
memset (buf, 0, l);
if (write (fd_out, buf, l) == l);
have_data = 0;
}
}
exit (0);
}
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