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

   1 #!/bin/bash
   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 -o pipefail -eux
  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_minimum_timestamp "$infile" "audio")"
  23     local videodelay="$(get_minimum_timestamp "$infile" "video")"
  24     local videotrackid="$(get_track_id "$infile" "video")"
  25
  26     mkvmerge \
  27         -o "${outfile}" \
  28         --default-duration "${videotrackid}:${FORCEFPS}fps" \
  29         --sync "${videotrackid}:$((videodelay / 1000000))" \
  30         --no-audio "$infile" \
  31         --sync "0:$((audiodelay / 1000000))" \
  32         "$audiofile"
  33 }
  34
  35 function get_track_id {
  36     mkvmerge -i -F json "$1" | jq -r ".tracks[] | select(.type == \"$2\") | .id"
  37 }
  38
  39 function get_minimum_timestamp {
  40     mkvmerge -F json -i "$1" | jq -r ".tracks[] | select(.type == \"$2\") | .properties.minimum_timestamp"
  41 }
  42
  43 function encode_audio {
  44     ffmpeg \
  45         -i "$1" \
  46         -vn \
  47         $SLOWFILTER \
  48         -c:a libfdk_aac -vbr 3 \
  49         "$2"
  50 }
  51
  52 function convert_file {
  53     local infile="$1"
  54     local outfile="$2"
  55     local audiofile="${tmpdir}/audiofile.m4a"
  56
  57     encode_audio "$infile" "$audiofile"
  58     mux_replace_audio "$infile" "$audiofile" "$outfile"
  59 }
  60
  61
  62 infile="$1"
  63 outfile="$2"
  64 tmpdir="$(mktemp -d "${TMPDIR:-/var/tmp}/pal-XXXXXXXX")"
  65 convert_file "$infile" "$outfile"
  66 rm -rf "$tmpdir"