Rob <[email protected]> wrote:
> Here is the sourcecode:
Thanks for that. I've tweaked it a little to actually generate the six
pips at the top of the minute. My ear can't detect a difference
between the BBC pips and these.
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <math.h>
#include <sys/time.h>
#include <sys/soundcard.h>
char *SoundDev = "/dev/dsp"; /* device name for soundcard */
#define FSAMP 8000 /* sample rate */
#define AMPLI 30000 /* output amplitude */
#define TONE 1000 /* tone freq */
#define DURA1 ((int)(0.1*FSAMP)) /* duration = 100 ms */
#define DURA2 ((int)(0.5*FSAMP)) /* duration = 500 ms */
#define RAMP ((int)(0.01*FSAMP)) /* ramp-down = 10 ms */
int
main (int argc, char **argv)
{
int soundfd,blksize,ampli;
int n,i;
double rate;
int nshort=5,sleep;
struct timeval time;
struct timezone tz;
short int sample[FSAMP*7];
/* Sleep until near the top of minute */
gettimeofday(&time,&tz);
sleep = 52-time.tv_sec %60;
if (sleep<0) sleep += 60;
usleep(sleep*1000000);
if ((soundfd = open(SoundDev,O_WRONLY)) < 0) {
perror(SoundDev);
exit(1);
}
n = APF_NETWORK; /* underruns occur */
ioctl(soundfd,SNDCTL_DSP_PROFILE,&n);
if (ioctl(soundfd,SNDCTL_DSP_GETBLKSIZE,&blksize) < 0 ||
blksize < 1 || blksize > 65536) {
perror(SoundDev);
exit(1);
}
/* Parameter +/-1 to add/subtract leap second e.g. pips 1 */
if (argc > 1) nshort += atoi(argv[1]);
n = 0; /* select MONO */
if (ioctl(soundfd,SNDCTL_DSP_STEREO,&n) < 0) {
perror(SoundDev);
exit(1);
}
n = AFMT_S16_LE; /* Little-endian signed 16bit */
if (ioctl(soundfd,SNDCTL_DSP_SETFMT,&n) < 0) {
perror(SoundDev);
exit(1);
}
n = FSAMP; /* sample rate */
if (ioctl(soundfd,SNDCTL_DSP_SPEED,&n) < 0) {
perror(SoundDev);
exit(1);
}
/* silence! */
memset(sample,0,sizeof(sample));
/* tone */
rate = ((double)TONE * 2 * M_PI) / (double)FSAMP;
/* Short pips */
for (i=0;i<nshort;i++) {
for (n = 0; n < DURA1; n++) {
if (n < RAMP)
/* ampli = n * AMPLI / RAMP;*/
ampli = AMPLI;
else
if (n > (DURA1 - RAMP))
ampli = (DURA1 - n) * AMPLI / RAMP;
else
ampli = AMPLI;
sample[i*FSAMP+n] = ampli * sin((double)n * rate);
}
}
/* Long pip on the minute */
for (n = 0; n < DURA2; n++) {
if (n < RAMP)
/* ampli = n * AMPLI / RAMP;*/
ampli = AMPLI;
else
if (n > (DURA2 - RAMP))
ampli = (DURA2 - n) * AMPLI / RAMP;
else
ampli = AMPLI;
sample[nshort*FSAMP+n] = ampli * sin((double)n * rate);
}
/* Busy wait for 55 second mark */
do
gettimeofday(&time,&tz);
while (time.tv_sec %60 != 55);
if (write(soundfd,sample,sizeof(sample)) != sizeof(sample)) {
perror(SoundDev);
exit(1);
}
if (close(soundfd) < 0) {
perror(SoundDev);
exit(1);
}
exit(0);
}
--
Dave Godfrey
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