code.delx.au - transcoding/blob - fix-pal-speedup

   1 #!/bin/bash -e
   2
   3 # Many DVDs released in Australia are sped up from 23.976fps to 25fps.
   4 # This script reverses the procedure, correcting the audio pitch.
   5 # Input files are assumed to be mkv files with track 2 audio.
   6 # The video framerate is adjusted without re-encoding. The audio is slowed and
   7 # normalised then re-encoded as mp3.
   8
   9 if [ -z "$1" -o -z "$2" ]; then
  10         echo "Usage: $0 destdir infile"
  11         exit 1
  12 fi
  13
  14 # FORCEFPS = 24000 / 1001
  15 # SLOWDOWN = FORCEFPS / 25
  16 FORCEFPS="23.976023976023978"
  17 SLOWDOWN="0.9590409590409591"
  18
  19 destdir="$1"
  20 infile="$2"
  21 outfile="$destdir/$(basename "$infile")"
  22 tmpdir="$(tempfile -p 'pal-')"
  23 rm "$tmpdir"
  24
  25 if [ -f "$outfile" ]; then
  26         echo "Not overwriting $outfile"
  27         exit 0
  28 fi
  29
  30 set -x
  31 mkdir "$tmpdir"
  32 mkvextract tracks "$infile" 2:"${tmpdir}/audio"
  33 mplayer -ao pcm:file="${tmpdir}/audio.wav" -vo null "${tmpdir}/audio"
  34 sox "${tmpdir}/audio.wav" "${tmpdir}/audio-fixed.wav" speed "${SLOWDOWN}" gain -n
  35 lame --preset standard "${tmpdir}/audio-fixed.wav" "${tmpdir}/audio.mp3"
  36 mkvmerge -o "${outfile}" --default-duration "1:${FORCEFPS}fps" --no-audio "$infile" "${tmpdir}/audio.mp3"
  37
  38 rm -rf "$tmpdir"
  39