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, volume normalised, down-mixed to stereo and encoded as mp3.
   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 SLOWDOWN="0.96"
  16
  17 function mux_replace_audio {
  18     infile="$1"
  19     audiofile="$2"
  20     outfile="$3"
  21
  22     trackid="$(mkvmerge -i "$infile" | grep video | sed 's/^Track ID \(.\):.*$/\1/')"
  23     exec mkvmerge -o "${outfile}" --default-duration "${trackid}:${FORCEFPS}fps" --no-audio "$infile" "$audiofile"
  24 }
  25
  26 function extract_audio {
  27     infile="$1"
  28
  29     exec mpv \
  30         --no-terminal \
  31         --no-video \
  32         --ao pcm:waveheader:file=/dev/stdout \
  33         "$infile"
  34 }
  35
  36 function slow_audio {
  37     exec sox \
  38         --temp "$tmpdir" \
  39         - \
  40         -t wav - \
  41         speed "${SLOWDOWN}" \
  42         gain -n \
  43         channels 2
  44 }
  45
  46 function encode_audio {
  47     outfile="$1"
  48     exec lame \
  49         --preset standard \
  50         - \
  51         "${outfile}"
  52 }
  53
  54 function convert_file {
  55     infile="$1"
  56     outfile="$2"
  57     tmpdir="$(mktemp -d "${TMPDIR:-/var/tmp}/pal-XXXXXXXX")"
  58     audiofile="${tmpdir}/audio.mp3"
  59
  60     extract_audio "${infile}" | slow_audio | encode_audio "${audiofile}"
  61     mux_replace_audio "${infile}" "${audiofile}" "${outfile}"
  62
  63     rm -rf "$tmpdir"
  64 }
  65
  66
  67 destdir="$1"
  68 shift
  69
  70 for infile in "$@"; do
  71     outfile="$destdir/$(basename "$infile")"
  72
  73     if [ -f "$outfile" ]; then
  74         echo "Not overwriting $outfile"
  75         continue
  76     fi
  77
  78     convert_file "$infile" "$outfile"
  79 done
  80