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Copyright (C) 4Front Technologies, 2007. All rights reserved.
This program is seriously broken. It's only purpose is to fail so that the !nlink SNDCTL_DSP_GETERROR
ioctl call can be tested. Otherwise this program is based on the singen.c program. }However this program demonstrates how SNDCTL_DSP_GETERROR can be used in applications.
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <fcntl.h>
#include <soundcard.h>
int fd_out;
static int
open_audio_device (char *name, int mode)
{
int tmp, fd;
int sample_rate;
if ((fd = open (name, mode, 0)) == -1)
{
perror (name);
exit (-1);
}
Setup the device. Note that it's important to set the sample format, number of channels and sample rate exactly in this order. Some devices depend on the order.
Set the sample format
tmp = AFMT_S16_NE; /* Native 16 bits */
if (ioctl (fd, SNDCTL_DSP_SETFMT, &tmp) == -1)
{
perror ("SNDCTL_DSP_SETFMT");
exit (-1);
}
if (tmp != AFMT_S16_NE)
{
fprintf (stderr,
"The device doesn't support the 16 bit sample format.\n");
exit (-1);
}
Set the number of channels
tmp = 1;
if (ioctl (fd, SNDCTL_DSP_CHANNELS, &tmp) == -1)
{
perror ("SNDCTL_DSP_CHANNELS");
exit (-1);
}
if (tmp != 1)
{
fprintf (stderr, "The device doesn't support mono mode.\n");
exit (-1);
}
Set the sample rate
sample_rate = 48000;
if (ioctl (fd, SNDCTL_DSP_SPEED, &sample_rate) == -1)
{
perror ("SNDCTL_DSP_SPEED");
exit (-1);
}
No need for error checking because we will automatically adjust the signal based on the actual sample rate. However most application must check the value of sample_rate and compare it to the requested rate.
Small differences between the rates (10% or less) are normal and the applications should usually tolerate them. However larger differences may cause annoying pitch problems (Mickey Mouse).
return fd;
}
int
main (int argc, char *argv[])
{
char *name_out = "/dev/dsp";
int tmp;
audio_errinfo ei;
audio_buf_info bi;
if (argc > 1)
name_out = argv[1];
fd_out = open_audio_device (name_out, O_WRONLY);
Cause an intentional error by using wrong parameter to SNDCTL_DSP_STEREO which expects 0 or 1. Don't do error checking in this case because we would like to see two errors reported.
tmp = 2; ioctl (fd_out, SNDCTL_DSP_STEREO, &tmp);
Cause an intentional failure by calling SNDCTL_DSP_GETISPACE which is not permitted on write-only devices.
if (ioctl (fd_out, SNDCTL_DSP_GETISPACE, &bi) == -1)
{
perror ("SNDCTL_DSP_GETISPACE"); /* Report the "primary" error first */
Next show the explanation to the user.
fprintf (stderr,
"Audio error: Cannot obtain recorded byte count from the device.\n");
fprintf (stderr, "\n");
Next call SNDCTL_DSP_GETERROR to see if there is any additional info available.
if (ioctl (fd_out, SNDCTL_DSP_GETERROR, &ei) != -1)
{
if (ei.play_errorcount > 0 && ei.play_lasterror != 0)
fprintf (stderr, "%d OSS play event(s), last=%05d:%d\n",
ei.play_errorcount, ei.play_lasterror,
ei.play_errorparm);
if (ei.rec_errorcount > 0 && ei.rec_lasterror != 0)
fprintf (stderr, "%d OSS rec event(s), last=%05d:%d\n",
ei.rec_errorcount, ei.rec_lasterror, ei.rec_errorparm);
}
}
else
fprintf (stderr, "SNDCTL_DSP_GETISPACE didn't fail as expected.\n");
exit (0);
}