git.sesse.net Git - audiosync/blob - do-skew.c

   1 #include <stdio.h>
   2 #include <string.h>
   3 #include <math.h>
   4 #include <stdlib.h>
   5
   6 double frac(double x)
   7 {
   8         return x - (int)x;
   9 }
  10
  11 int main(int argc, char **argv)
  12 {
  13         FILE *in, *skew, *out;
  14
  15         // open input
  16         if (strcmp(argv[1], "-") == 0) {
  17                 in = stdin;
  18         } else {
  19                 in = fopen(argv[1], "rb");
  20                 if (in == NULL) {
  21                         perror(argv[1]);
  22                         exit(1);
  23                 }
  24         }
  25
  26         // open skew
  27         if (strcmp(argv[2], "-") == 0) {
  28                 skew = stdin;
  29         } else {
  30                 skew = fopen(argv[2], "rb");
  31                 if (skew == NULL) {
  32                         perror(argv[2]);
  33                         exit(1);
  34                 }
  35         }
  36
  37         // open output
  38         if (strcmp(argv[3], "-") == 0) {
  39                 out = stderr;
  40         } else {
  41                 out = fopen(argv[3], "wb");
  42                 if (in == NULL) {
  43                         perror(argv[3]);
  44                         exit(1);
  45                 }
  46         }
  47
  48         short prev_sample, sample = 0;
  49         int in_pos = -1;
  50         double p = -1.0;
  51
  52         while (!feof(in) && !feof(skew)) {
  53                 double delta_p;
  54                 if (fread(&delta_p, sizeof(double), 1, skew) != 1) {
  55                         exit(0);
  56                 }
  57
  58                 p += delta_p;
  59
  60                 // read samples until we're at the right position
  61                 while ((int)(ceil(p)) > in_pos) {
  62                         prev_sample = sample;
  63                         if (fread(&sample, sizeof(short), 1, in) != 1) {
  64                                 exit(0);
  65                         }
  66                         ++in_pos;
  67                 }
  68
  69                 // linear interpolation (works well since delta_p varies so slowly)
  70                 double t = frac(p);
  71                 short intp_sample = prev_sample * (1.0 - t) + sample * t;
  72
  73                 fwrite(&intp_sample, sizeof(short), 1, out);
  74         }
  75 }