channels/gentone-ulaw.c

   1 /* Generate a header file for a particular
   2    single or double frequency */
   3
   4 #include <stdio.h>
   5 #include <math.h>
   6 #include <string.h>
   7 #include <unistd.h>
   8 #include <stdlib.h>
   9 #define CLIP 32635
  10 #define BIAS 0x84
  11 static float loudness=16384.0;
  12
  13 static int calc_samples(int freq)
  14 {
  15         int x, samples;
  16         /* Calculate the number of samples at 8000hz sampling
  17            we need to have this wave form */
  18         samples = 8000;
  19         /* Take out common 2's up to six times */
  20         for (x=0;x<6;x++)
  21                 if (!(freq % 2)) {
  22                         freq /= 2;
  23                         samples /= 2;
  24                 }
  25         /* Take out common 5's (up to three times */
  26         for (x=0;x<3;x++)
  27                 if (!(freq % 5)) {
  28                         freq /= 5;
  29                         samples /=5;
  30                 }
  31         /* No more common factors. */
  32         return samples;
  33 }
  34
  35 /*
  36 ** This routine converts from linear to ulaw
  37 **
  38 ** Craig Reese: IDA/Supercomputing Research Center
  39 ** Joe Campbell: Department of Defense
  40 ** 29 September 1989
  41 **
  42 ** References:
  43 ** 1) CCITT Recommendation G.711  (very difficult to follow)
  44 ** 2) "A New Digital Technique for Implementation of Any
  45 **     Continuous PCM Companding Law," Villeret, Michel,
  46 **     et al. 1973 IEEE Int. Conf. on Communications, Vol 1,
  47 **     1973, pg. 11.12-11.17
  48 ** 3) MIL-STD-188-113,"Interoperability and Performance Standards
  49 **     for Analog-to_Digital Conversion Techniques,"
  50 **     17 February 1987
  51 **
  52 ** Input: Signed 16 bit linear sample
  53 ** Output: 8 bit ulaw sample
  54 */
  55
  56 #define ZEROTRAP    /* turn on the trap as per the MIL-STD */
  57 #define BIAS 0x84   /* define the add-in bias for 16 bit samples */
  58 #define CLIP 32635
  59
  60 static unsigned char linear2ulaw(short sample) {
  61 static int exp_lut[256] = {0,0,1,1,2,2,2,2,3,3,3,3,3,3,3,3,
  62                              4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
  63                              5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
  64                              5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
  65                              6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
  66                              6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
  67                              6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
  68                              6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
  69                              7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
  70                              7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
  71                              7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
  72                              7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
  73                              7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
  74                              7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
  75                              7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
  76                              7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7};
  77   int sign, exponent, mantissa;
  78   unsigned char ulawbyte;
  79
  80   /* Get the sample into sign-magnitude. */
  81   sign = (sample >> 8) & 0x80;          /* set aside the sign */
  82   if (sign != 0) sample = -sample;              /* get magnitude */
  83   if (sample > CLIP) sample = CLIP;             /* clip the magnitude */
  84
  85   /* Convert from 16 bit linear to ulaw. */
  86   sample = sample + BIAS;
  87   exponent = exp_lut[(sample >> 7) & 0xFF];
  88   mantissa = (sample >> (exponent + 3)) & 0x0F;
  89   ulawbyte = ~(sign | (exponent << 4) | mantissa);
  90 #ifdef ZEROTRAP
  91   if (ulawbyte == 0) ulawbyte = 0x02;   /* optional CCITT trap */
  92 #endif
  93
  94   return(ulawbyte);
  95 }
  96
  97 int main(int argc, char *argv[])
  98 {
  99         FILE *f;
 100         int freq1, freq2;
 101         float wlen1, wlen2;
 102         float val;
 103         int x, samples1, samples2, samples=0;
 104         char fn[256];
 105         if (argc < 3) {
 106                 fprintf(stderr, "Usage: gensound <name> <freq1> [freq2]\n");
 107                 exit(1);
 108         }
 109         freq1 = atoi(argv[2]);
 110         if (argc > 3)
 111                 freq2 = atoi(argv[3]);
 112         else
 113                 freq2 = 0;
 114         wlen1 = 8000.0/(float)freq1;
 115         samples1 = calc_samples(freq1);
 116         printf("Wavelength 1 (in samples): %10.5f\n", wlen1);
 117         printf("Minimum samples (1): %d (%f.3 wavelengths)\n", samples1, samples1 / wlen1);
 118         if (freq2) {
 119                 wlen2 = 8000.0/(float)freq2;
 120                 samples2 = calc_samples(freq2);
 121                 printf("Wavelength 1 (in samples): %10.5f\n", wlen2);
 122                 printf("Minimum samples (1): %d (%f.3 wavelengths)\n", samples2, samples2 / wlen2);
 123         }
 124         samples = samples1;
 125         if (freq2) {
 126                 while(samples % samples2)
 127                         samples += samples1;
 128         }
 129         printf("Need %d samples\n", samples);
 130         snprintf(fn, sizeof(fn), "%s.h", argv[1]);
 131         if ((f = fopen(fn, "w"))) {
 132                 if (freq2)
 133                         fprintf(f, "/* %s: Generated from frequencies %d and %d \n"
 134                                    "   by gentone.  %d samples  */\n", fn, freq1, freq2, samples);
 135                 else
 136                         fprintf(f, "/* %s: Generated from frequency %d\n"
 137                                    "   by gentone.  %d samples  */\n", fn, freq1, samples);
 138                 fprintf(f, "static unsigned char %s[%d] = {\n\t", argv[1], samples);
 139                 for (x=0;x<samples;x++) {
 140                         val = loudness * sin((freq1 * 2.0 * M_PI * x)/8000.0);
 141                         if (freq2)
 142                                 val += loudness * sin((freq2 * 2.0 * M_PI * x)/8000.0);
 143                         fprintf(f, "%3d, ", (int) linear2ulaw(val));
 144                         if (!((x+1) % 8))
 145                                 fprintf(f, "\n\t");
 146                 }
 147                 if (x % 15)
 148                         fprintf(f, "\n");
 149                 fprintf(f, "};\n");
 150                 fclose(f);
 151                 printf("Wrote %s\n", fn);
 152         } else {
 153                 fprintf(stderr, "Unable to open %s for writing\n", fn);
 154                 return 1;
 155         }
 156         return 0;
 157 }