TOOLS/calcbpp.pl

   1 #!/usr/bin/perl -w
   2
   3 use POSIX;
   4
   5 sub round {
   6   my $v = shift;
   7
   8   return floor($v + 0.5);
   9 }
  10
  11 $raw_aspect = 720/576;
  12
  13 if (scalar(@ARGV) < 4) {
  14   print("Please provide a) the cropped but unscaled resolution (e.g. " .
  15         "716x524), b) the aspect ratio (either 4/3 or 16/9 for most DVDs), " .
  16         "c) the video bitrate in kbps (e.g. 800) and d) the movie's fps.\n");
  17   print("If your DVD is not encoded at 720x576 then change the \$raw_aspect" .
  18         "variable at the beginning of this script.\n");
  19   exit(1);
  20 }
  21
  22 ($unscaled_width, $unscaled_height) = split('x', $ARGV[0]);
  23 $encoded_at = $ARGV[1];
  24 if ($encoded_at =~ /\//) {
  25   my @a = split(/\//, $encoded_at);
  26   $encoded_at = $a[0] / $a[1];
  27 }
  28 $scaled_width = $unscaled_width * ($encoded_at / ($raw_aspect));
  29 $scaled_height = $unscaled_height;
  30 $picture_ar = $scaled_width / $scaled_height;
  31 ($bps, $fps) = @ARGV[2, 3];
  32
  33 printf("Prescaled picture: %dx%d, AR %.2f\n", $scaled_width, $scaled_height,
  34        $picture_ar);
  35 for ($width = 720; $width >= 320; $width -= 16) {
  36   $height = 16 * round($width / $picture_ar / 16);
  37   $diff = round($width / $picture_ar - $height);
  38   $new_ar = $width / $height;
  39   $picture_ar_error = abs(100 - $picture_ar / $new_ar * 100);
  40   printf("${width}x${height}, diff % 3d, new AR %.2f, AR error %.2f%% " .
  41          "scale=%d:%d bpp: %.3f\n", $diff, $new_ar, $picture_ar_error, $width,
  42          $height, ($bps * 1000) / ($width * $height * $fps));
  43 }