# 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, and encoded as AAC, preserving surround sound.
if [ -z "$1" -o -z "$2" ]; then
- echo "Usage: $0 destdir infile [infile ...]"
- exit 1
+ echo "Usage: $0 destdir infile [infile ...]"
+ exit 1
fi
+set -xe
FORCEFPS="24"
-SLOWDOWN="0.96"
+SLOWFILTER="-filter asetrate=46080,aresample=osr=48000:resampler=soxr"
+
+function mux_replace_audio {
+ local infile="$1"
+ local audiofile="$2"
+ local outfile="$3"
+
+ local trackid="$(mkvmerge -i "$infile" | grep 'Track ID.*video' | sed 's/^Track ID \(.\):.*$/\1/')"
+ mkvmerge -o "${outfile}" --default-duration "${trackid}:${FORCEFPS}fps" --no-audio "$infile" "$audiofile"
+}
+
+function encode_audio {
+ ffmpeg \
+ -i "$1" \
+ -vn \
+ $SLOWFILTER \
+ -c:a libfdk_aac -vbr 3 \
+ "$2"
+}
+
+function convert_file {
+ local infile="$1"
+ local outfile="$2"
+ local audiofile="${tmpdir}/audiofile.m4a"
+
+ encode_audio "${infile}" "${audiofile}"
+ mux_replace_audio "${infile}" "${audiofile}" "${outfile}"
+}
+
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"
+ tmpdir="$(mktemp -d "${TMPDIR:-/var/tmp}/pal-XXXXXXXX")"
+ convert_file "$infile" "$outfile"
+ rm -rf "$tmpdir"
done