mixer_info.c

在linux下多媒体开发实例linux下多媒体开发

/*
 * mixer_info.c
 * Example program to display mixer settings.
 */

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

/* utility function for printing status */
void yes_no(int condition)
{
  condition ? printf("  yes      ") : printf("  no       ");
}

int main(int argc, char *argv[])
{
  int fd;       /* file descriptor for mixer device */
  int i;        /* loop counter */
  int level;    /* volume setting */
  char *device; /* name of device to report on */
  int status;   /* status of system calls */
  /* various device settings */
  int recsrc, devmask, recmask, stereodevs, caps;
  /* names of available mixer channels */
  const char *sound_device_names[] = SOUND_DEVICE_LABELS;

  /* get device name from command line or use default */  
  if (argc == 2)
    device = argv[1];
  else
    device = "/dev/mixer";

  /* open mixer, read only */
  fd = open(device, O_RDONLY);
  if (fd == -1) {
    fprintf(stderr, "%s: unable to open `%s', ", argv[0], device);
    perror("");
    return 1;
  }

  /* get all of the information about the mixer */
  status = ioctl(fd, SOUND_MIXER_READ_RECSRC, &recsrc);
  if (status == -1)
    perror("SOUND_MIXER_READ_RECSRC ioctl failed");
  status = ioctl(fd, SOUND_MIXER_READ_DEVMASK, &devmask);
  if (status == -1)
    perror("SOUND_MIXER_READ_DEVMASK ioctl failed");
  status = ioctl(fd, SOUND_MIXER_READ_RECMASK, &recmask);
  if (status == -1)
    perror("SOUND_MIXER_READ_RECMASK ioctl failed");
  status = ioctl(fd, SOUND_MIXER_READ_STEREODEVS, &stereodevs);
  if (status == -1)
    perror("SOUND_MIXER_READ_STEREODEVS ioctl failed");
  status = ioctl(fd, SOUND_MIXER_READ_CAPS, &caps);
  if (status == -1)
    perror("SOUND_MIXER_READ_CAPS ioctl failed");

  /* print results in a table */
  printf(
	 "Status of %s:\n\n"
	 "Mixer      Device     Recording  Active     Stereo     Current\n"
	 "Channel    Available  Source     Source     Device     Level\n"
	 "---------  ---------  ---------  --------   ---------  ---------\n",
	 device
	 );

  /* loop over all devices */
  for (i = 0 ; i < SOUND_MIXER_NRDEVICES ; i++) {
    /* print number and name */
    printf("%2d %-7s", i, sound_device_names[i]);
    /* print if available */
    yes_no((1 << i) & devmask);
    /* can it be used as a recording source? */
    yes_no((1 << i) & recmask);
    /* it it an active recording source? */
    yes_no((1 << i) & recsrc);
    /* does it have stereo capability? */
    yes_no((1 << i) & stereodevs);
    /* if available, display current level */
    if ((1 << i) & devmask) { 
      /* if stereo, show both levels */
      if ((1 << i) & stereodevs) {
	status = ioctl(fd, MIXER_READ(i), &level);
	if (status == -1)
	  perror("SOUND_MIXER_READ ioctl failed");
	printf("  %d%% %d%%", level & 0xff, (level & 0xff00) >> 8);
      } else { /* only one channel */
	status = ioctl(fd, MIXER_READ(i), &level);
	if (status == -1)
	  perror("SOUND_MIXER_READ ioctl failed");
	printf("  %d%%", level & 0xff);
      }
  } 
    printf("\n");
  }
  printf("\n");
  /* are recording sources exclusive? */
  printf("Note: Choices for recording source are ");
  if (!(caps & SOUND_CAP_EXCL_INPUT))
    printf("not ");
  printf("exclusive.\n");
  /* close mixer device */
  close(fd);
  return 0;
}