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

   1 #!/bin/bash -e
   2
   3 # Many DVDs released in Australia are sped up from 24fps to 25fps.
   4 # This script reverses the procedure, correcting the audio pitch.
   5 # The video framerate is adjusted without re-encoding. The audio is
   6 # slowed, and encoded as AAC, preserving surround sound.
   7
   8 if [ -z "$1" -o -z "$2" ]; then
   9     echo "Usage: $0 destdir infile [infile ...]"
  10     exit 1
  11 fi
  12
  13 set -xe
  14 FORCEFPS="24"
  15 SLOWFILTER="-filter asetrate=46080,aresample=48000"
  16
  17 function mux_replace_audio {
  18     local infile="$1"
  19     local audiofile="$2"
  20     local outfile="$3"
  21
  22     local trackid="$(mkvmerge -i "$infile" | grep 'Track ID.*video' | sed 's/^Track ID \(.\):.*$/\1/')"
  23     mkvmerge -o "${outfile}" --default-duration "${trackid}:${FORCEFPS}fps" --no-audio "$infile" "$audiofile"
  24 }
  25
  26 function extract_audio {
  27     local infile="$1"
  28     local outfile="$2"
  29
  30     mplayer \
  31         -noconfig all \
  32         -novideo \
  33         -channels 8 \
  34         -dumpaudio \
  35         -dumpfile "$outfile" \
  36         "$infile"
  37 }
  38
  39 function encode_audio {
  40     ffmpeg \
  41         -i "$1" \
  42         $SLOWFILTER \
  43         -strict experimental \
  44         "$2"
  45 }
  46
  47 function convert_file {
  48     local infile="$1"
  49     local outfile="$2"
  50     local audio1="${tmpdir}/audio1.ac3"
  51     local audio2="${tmpdir}/audio2.m4a"
  52
  53     extract_audio "${infile}" "${audio1}"
  54     encode_audio "${audio1}" "${audio2}"
  55     mux_replace_audio "${infile}" "${audio2}" "${outfile}"
  56 }
  57
  58
  59 destdir="$1"
  60 shift
  61
  62 for infile in "$@"; do
  63     outfile="$destdir/$(basename "$infile")"
  64
  65     if [ -f "$outfile" ]; then
  66         echo "Not overwriting $outfile"
  67         continue
  68     fi
  69
  70     tmpdir="$(mktemp -d "${TMPDIR:-/var/tmp}/pal-XXXXXXXX")"
  71     convert_file "$infile" "$outfile"
  72     rm -rf "$tmpdir"
  73 done
  74