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 infile outfile"
  10     exit 1
  11 fi
  12
  13 set -xe
  14 FORCEFPS="24"
  15 SLOWFILTER="-filter asetrate=46080,aresample=osr=48000:resampler=soxr"
  16
  17 function mux_replace_audio {
  18     local infile="$1"
  19     local audiofile="$2"
  20     local outfile="$3"
  21
  22     local audiodelay="$(get_audio_delay "$infile")"
  23     local videotrackid="$(get_video_trackid "$infile")"
  24
  25     mkvmerge \
  26         -o "${outfile}" \
  27         --default-duration "${videotrackid}:${FORCEFPS}fps" \
  28         --no-audio "$infile" \
  29         --sync "0:$((audiodelay / 1000000))" \
  30         "$audiofile"
  31 }
  32
  33 function get_video_trackid {
  34     mkvmerge -i "$1" | sed -n 's/Track ID \([0-9]*\): .*video.*/\1/p'
  35 }
  36
  37 function get_audio_delay {
  38     mkvmerge -F verbose-text -i "$1" | \
  39         sed -n 's/Track ID [0-9]*: .*audio.*minimum_timestamp:\([0-9]*\).*/\1/p'
  40 }
  41
  42 function encode_audio {
  43     ffmpeg \
  44         -i "$1" \
  45         -vn \
  46         $SLOWFILTER \
  47         -c:a libfdk_aac -vbr 3 \
  48         "$2"
  49 }
  50
  51 function convert_file {
  52     local infile="$1"
  53     local outfile="$2"
  54     local audiofile="${tmpdir}/audiofile.m4a"
  55
  56     encode_audio "$infile" "$audiofile"
  57     mux_replace_audio "$infile" "$audiofile" "$outfile"
  58 }
  59
  60
  61 infile="$1"
  62 outfile="$2"
  63 tmpdir="$(mktemp -d "${TMPDIR:-/var/tmp}/pal-XXXXXXXX")"
  64 convert_file "$infile" "$outfile"
  65 rm -rf "$tmpdir"