func: static void opt_frame_size(const char *arg)
  
  {
  
      if (av_parse_video_frame_size(&frame_width, &frame_height, arg) < 0) {
  
          fprintf(stderr, "Incorrect frame size\n");
  
          av_exit(1);
  
      }
  
      if ((frame_width % 2) != 0 || (frame_height % 2) != 0) {
  
          fprintf(stderr, "Frame size must be a multiple of 2\n");
  
          av_exit(1);
  
      }
  
  }
  