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/* Generate a header file for a particular
single or double frequency */
#include <stdio.h>
#include <math.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#define CLIP 32635
#define BIAS 0x84
static float loudness=16384.0;
static int calc_samples(int freq)
{
int x, samples;
/* Calculate the number of samples at 8000hz sampling
we need to have this wave form */
samples = 8000;
/* Take out common 2's up to six times */
for (x=0;x<6;x++)
if (!(freq % 2)) {
freq /= 2;
samples /= 2;
}
/* Take out common 5's (up to three times */
for (x=0;x<3;x++)
if (!(freq % 5)) {
freq /= 5;
samples /=5;
}
/* No more common factors. */
return samples;
}
/*
** This routine converts from linear to ulaw
**
** Craig Reese: IDA/Supercomputing Research Center
** Joe Campbell: Department of Defense
** 29 September 1989
**
** References:
** 1) CCITT Recommendation G.711 (very difficult to follow)
** 2) "A New Digital Technique for Implementation of Any
** Continuous PCM Companding Law," Villeret, Michel,
** et al. 1973 IEEE Int. Conf. on Communications, Vol 1,
** 1973, pg. 11.12-11.17
** 3) MIL-STD-188-113,"Interoperability and Performance Standards
** for Analog-to_Digital Conversion Techniques,"
** 17 February 1987
**
** Input: Signed 16 bit linear sample
** Output: 8 bit ulaw sample
*/
#define ZEROTRAP /* turn on the trap as per the MIL-STD */
#define BIAS 0x84 /* define the add-in bias for 16 bit samples */
#define CLIP 32635
static unsigned char linear2ulaw(short sample) {
static int exp_lut[256] = {0,0,1,1,2,2,2,2,3,3,3,3,3,3,3,3,
4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7};
int sign, exponent, mantissa;
unsigned char ulawbyte;
/* Get the sample into sign-magnitude. */
sign = (sample >> 8) & 0x80; /* set aside the sign */
if (sign != 0) sample = -sample; /* get magnitude */
if (sample > CLIP) sample = CLIP; /* clip the magnitude */
/* Convert from 16 bit linear to ulaw. */
sample = sample + BIAS;
exponent = exp_lut[(sample >> 7) & 0xFF];
mantissa = (sample >> (exponent + 3)) & 0x0F;
ulawbyte = ~(sign | (exponent << 4) | mantissa);
#ifdef ZEROTRAP
if (ulawbyte == 0) ulawbyte = 0x02; /* optional CCITT trap */
#endif
return(ulawbyte);
}
int main(int argc, char *argv[])
{
FILE *f;
int freq1, freq2;
float wlen1, wlen2;
float val;
int x, samples1, samples2, samples=0;
char fn[256];
if (argc < 3) {
fprintf(stderr, "Usage: gensound <name> <freq1> [freq2]\n");
exit(1);
}
freq1 = atoi(argv[2]);
if (argc > 3)
freq2 = atoi(argv[3]);
else
freq2 = 0;
wlen1 = 8000.0/(float)freq1;
samples1 = calc_samples(freq1);
printf("Wavelength 1 (in samples): %10.5f\n", wlen1);
printf("Minimum samples (1): %d (%f.3 wavelengths)\n", samples1, samples1 / wlen1);
if (freq2) {
wlen2 = 8000.0/(float)freq2;
samples2 = calc_samples(freq2);
printf("Wavelength 1 (in samples): %10.5f\n", wlen2);
printf("Minimum samples (1): %d (%f.3 wavelengths)\n", samples2, samples2 / wlen2);
}
samples = samples1;
if (freq2) {
while(samples % samples2)
samples += samples1;
}
printf("Need %d samples\n", samples);
snprintf(fn, sizeof(fn), "%s.h", argv[1]);
if ((f = fopen(fn, "w"))) {
if (freq2)
fprintf(f, "/* %s: Generated from frequencies %d and %d \n"
" by gentone. %d samples */\n", fn, freq1, freq2, samples);
else
fprintf(f, "/* %s: Generated from frequency %d\n"
" by gentone. %d samples */\n", fn, freq1, samples);
fprintf(f, "static unsigned char %s[%d] = {\n\t", argv[1], samples);
for (x=0;x<samples;x++) {
val = loudness * sin((freq1 * 2.0 * M_PI * x)/8000.0);
if (freq2)
val += loudness * sin((freq2 * 2.0 * M_PI * x)/8000.0);
fprintf(f, "%3d, ", (int) linear2ulaw(val));
if (!((x+1) % 8))
fprintf(f, "\n\t");
}
if (x % 15)
fprintf(f, "\n");
fprintf(f, "};\n");
fclose(f);
printf("Wrote %s\n", fn);
} else {
fprintf(stderr, "Unable to open %s for writing\n", fn);
return 1;
}
return 0;
}