#define W 400
#define H 200

void waveform_viewer(Audio *a, unsigned long samples)
{
   unsigned long samples_per_pixel;
   unsigned long x;
   unsigned long offset;
   double min;
   double max;
   double v;
   
   samples_per_pixel = samples / W;
   
   for(x = 0; x < W; ++x) {
      min = 1;
      max = 0;
      for(offset = 0; offset < samples_per_pixels; ++offset) {
         v = a[x * samples_per_pixel + offset];
         if(v > max) max = v;
         if(v < min) min = v;
      }
      draw_line(x, min * H, x, max * H);
   }
}