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     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="$2"
  29
  30     mpv \
  31         --no-terminal \
  32         --no-video \
  33         --ao "pcm:waveheader:file=${outfile}" \
  34         "$infile"
  35 }
  36
  37 function slow_audio {
  38     local infile="$1"
  39     local outfile="$2"
  40
  41     sox \
  42         --temp "$tmpdir" \
  43         "$infile" \
  44         -t wav \
  45         "$outfile" \
  46         speed "${SLOWDOWN}" \
  47         gain -n \
  48         channels 2
  49 }
  50
  51 function encode_audio {
  52     local infile="$1"
  53     local outfile="$2"
  54
  55     lame \
  56         --preset standard \
  57         "${infile}" "${outfile}"
  58 }
  59
  60 function convert_file {
  61     local infile="$1"
  62     local outfile="$2"
  63     local audio1="${tmpdir}/audio1.wav"
  64     local audio2="${tmpdir}/audio2.wav"
  65     local audio3="${tmpdir}/audio3.mp3"
  66
  67     extract_audio "${infile}" "${audio1}"
  68     slow_audio "${audio1}" "${audio2}"
  69     encode_audio "${audio2}" "${audio3}"
  70     mux_replace_audio "${infile}" "${audio3}" "${outfile}"
  71 }
  72
  73
  74 destdir="$1"
  75 shift
  76
  77 for infile in "$@"; do
  78     outfile="$destdir/$(basename "$infile")"
  79
  80     if [ -f "$outfile" ]; then
  81         echo "Not overwriting $outfile"
  82         continue
  83     fi
  84
  85     tmpdir="$(mktemp -d "${TMPDIR:-/var/tmp}/pal-XXXXXXXX")"
  86     convert_file "$infile" "$outfile"
  87     rm -rf "$tmpdir"
  88 done
  89