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="$3"
  21
  22     local trackid="$(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 encode_audio {
  27     ffmpeg \
  28         -i "$1" \
  29         -vn \
  30         $SLOWFILTER \
  31         -c:a libfdk_aac -vbr 3 \
  32         "$2"
  33 }
  34
  35 function convert_file {
  36     local infile="$1"
  37     local outfile="$2"
  38     local audiofile="${tmpdir}/audiofile.m4a"
  39
  40     encode_audio "${infile}" "${audiofile}"
  41     mux_replace_audio "${infile}" "${audiofile}" "${outfile}"
  42 }
  43
  44
  45 infile="$1"
  46 outfile="$2"
  47 tmpdir="$(mktemp -d "${TMPDIR:-/var/tmp}/pal-XXXXXXXX")"
  48 convert_file "$infile" "$outfile"
  49 rm -rf "$tmpdir"