# Many DVDs released in Australia are sped up from 24fps to 25fps.
# This script reverses the procedure, correcting the audio pitch.
-# The video framerate is adjusted without re-encoding. The audio is slowed and
-# volume normalised then re-encoded as mp3.
+# The video framerate is adjusted without re-encoding. The audio is
+# slowed, volume normalised, down-mixed to stereo and encoded as mp3.
if [ -z "$1" -o -z "$2" ]; then
- echo "Usage: $0 destdir infile [infile ...]"
- exit 1
+ echo "Usage: $0 destdir infile [infile ...]"
+ exit 1
fi
FORCEFPS="24"
SLOWDOWN="0.96"
+function mux_replace_audio {
+ infile="$1"
+ audiofile="$2"
+ outfile="$3"
+
+ set -x
+ trackid="$(mkvmerge -i "$infile" | grep video | sed 's/^Track ID \(.\):.*$/\1/')"
+ mkvmerge -o "${outfile}" --default-duration "${trackid}:${FORCEFPS}fps" --no-audio "$infile" "$audiofile"
+}
+
+function extract_audio {
+ infile="$1"
+
+ mpv \
+ --no-terminal \
+ --no-video \
+ --ao pcm:waveheader:file=/dev/stdout \
+ "$infile"
+}
+
+function slow_audio {
+ sox \
+ --temp "$tmpdir" \
+ /dev/stdin \
+ -t wav /dev/stdout \
+ speed "${SLOWDOWN}" \
+ gain -n \
+ channels 2
+}
+
+function encode_audio {
+ outfile="$1"
+ lame \
+ --preset standard \
+ /dev/stdin \
+ "${outfile}"
+}
+
+function convert_file {
+ set -xe
+ infile="$1"
+ outfile="$2"
+ tmpdir="$(mktemp -d "${TMPDIR:-/var/tmp}/pal-XXXXXXXX")"
+ audiofile="${tmpdir}/audio.mp3"
+
+ extract_audio "${infile}" | slow_audio | encode_audio "${audiofile}"
+ mux_replace_audio "${infile}" "${audiofile}" "${outfile}"
+
+ rm -rf "$tmpdir"
+}
+
+
destdir="$1"
shift
for infile in "$@"; do
- outfile="$destdir/$(basename "$infile")"
-
- if [ -f "$outfile" ]; then
- echo "Not overwriting $outfile"
- continue
- fi
+ outfile="$destdir/$(basename "$infile")"
- set -x
- tmpdir="$(mktemp -d "${TMPDIR:-/var/tmp}/pal-XXXXXXXX")"
- mplayer -novideo -ao pcm:file="${tmpdir}/audio.wav" -vo null "$infile"
- sox "${tmpdir}/audio.wav" "${tmpdir}/audio-fixed.wav" speed "${SLOWDOWN}" gain -n
- lame --preset standard "${tmpdir}/audio-fixed.wav" "${tmpdir}/audio.mp3"
- mkvmerge -o "${outfile}" --default-duration "1:${FORCEFPS}fps" --no-audio "$infile" "${tmpdir}/audio.mp3"
+ if [ -f "$outfile" ]; then
+ echo "Not overwriting $outfile"
+ continue
+ fi
- rm -rf "$tmpdir"
+ convert_file "$infile" "$outfile"
done