linux commandline vol control

[plasmator]

/*
* mixer.c
* Example of a simple mixer program
*/

#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <linux/soundcard.h>

/* names of available mixer devices */
const char *sound_device_names[] = SOUND_DEVICE_NAMES;

int fd; /* file descriptor for mixer device */
int devmask, stereodevs; /* bit masks of mixer information */
char *name; /* program name */

/* display command usage and exit with error status */
void usage()
{
int i;

fprintf(stderr, "usage: %s <device> <left-gain%%> <right-gain%%>n"
" %s <device> <gain%%>nn"
"Where <device> is one of:n", name, name);
for (i = 0 ; i < SOUND_MIXER_NRDEVICES ; i++)
if ((1 << i) & devmask) /* only display valid devices */
fprintf(stderr, "%s ", sound_device_names[i]);
fprintf(stderr, "n");
exit(1);
}

int main(int argc, char *argv[])
{
int left, right, level; /* gain settings */
int status; /* return value from system calls */
int device; /* which mixer device to set */
int i; /* general purpose loop counter */
char *dev; /* mixer device name */

/* save program name */
name = argv[0];

/* open mixer, read only */
fd = open("/dev/mixer", O_RDONLY);
if (fd == -1) {
perror("unable to open /dev/mixer");
exit(1);
}

/* get needed information about the mixer */
status = ioctl(fd, SOUND_MIXER_READ_DEVMASK, &devmask);
if (status == -1)
perror("SOUND_MIXER_READ_DEVMASK ioctl failed");
status = ioctl(fd, SOUND_MIXER_READ_STEREODEVS, &stereodevs);
if (status == -1)
perror("SOUND_MIXER_READ_STEREODEVS ioctl failed");

/* check that user passed two or three arguments on command line */
if (argc != 3 && argc != 4)
usage();

/* save mixer device name */
dev = argv[1];

/* figure out which device to use */
for (i = 0 ; i < SOUND_MIXER_NRDEVICES ; i++)
if (((1 << i) & devmask) && !strcmp(dev, sound_device_names[i]))
break;
if (i == SOUND_MIXER_NRDEVICES) { /* didn't find a match */
fprintf(stderr, "%s is not a valid mixer devicen", dev);
usage();
}

/* we have a valid mixer device */
device = i;

/* get gain values */
if (argc == 4) {
/* both left and right values given */
left = atoi(argv[2]);
right = atoi(argv[3]);
} else {
/* left and right are the same */
left = atoi(argv[2]);
right = atoi(argv[2]);
}

/* display warning if left and right gains given for non-stereo device */
if ((left != right) && !((1 << i) & stereodevs)) {
fprintf(stderr, "warning: %s is not a stereo devicen", dev);
}

/* encode both channels into one value */
level = (right << 8 ) + left;

/* set gain */
status = ioctl(fd, MIXER_WRITE(device), &level);
if (status == -1) {
perror("MIXER_WRITE ioctl failed");
exit(1);
}

/* unpack left and right levels returned by sound driver */
left = level & 0xff;
right = (level & 0xff00) >> 8;

/* display actual gain setting */
fprintf(stderr, "%s gain set to %d%% / %d%%n", dev, left, right);

/* close mixer device and exit */
close(fd);
return 0;
}



[ This Message was edited by: plasmator on 2003-12-22 20:43 ]

[plasmator]

mmmh it made a out of some source code...(i corrected it ) 8 ) not

just save this as mixer.c

then

gcc mixer.c
cp a.out mixer



[ This Message was edited by: plasmator on 2003-12-22 20:45 ]

[JaM]

There is something like