# 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, volume normalised, down-mixed to stereo and encoded as mp3.
+# slowed, and encoded as AAC, preserving surround sound.
if [ -z "$1" -o -z "$2" ]; then
echo "Usage: $0 destdir infile [infile ...]"
exit 1
fi
+set -xe
FORCEFPS="24"
-SLOWDOWN="0.96"
+SLOWFILTER="-filter asetrate=46080,aresample=48000"
function mux_replace_audio {
- infile="$1"
- audiofile="$2"
- outfile="$3"
+ local infile="$1"
+ local audiofile="$2"
+ local outfile="$3"
- set -x
- trackid="$(mkvmerge -i "$infile" | grep video | sed 's/^Track ID \(.\):.*$/\1/')"
+ local trackid="$(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 extract_audio {
- infile="$1"
-
- mpv \
- --no-terminal \
- --no-video \
- --ao pcm:waveheader:file=/dev/stdout \
+ local infile="$1"
+ local outfile="$2"
+
+ mplayer \
+ -noconfig all \
+ -novideo \
+ -channels 8 \
+ -dumpaudio \
+ -dumpfile "$outfile" \
"$infile"
}
-function slow_audio {
- sox \
- --temp "$tmpdir" \
- /dev/stdin \
- -t wav /dev/stdout \
- speed "${SLOWDOWN}" \
- gain -n \
- channels 2
-}
-
function encode_audio {
- outfile="$1"
- lame \
- --preset standard \
- /dev/stdin \
- "${outfile}"
+ ffmpeg \
+ -i "$1" \
+ $SLOWFILTER \
+ -strict experimental \
+ "$2"
}
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"
+ local infile="$1"
+ local outfile="$2"
+ local audio1="${tmpdir}/audio1.ac3"
+ local audio2="${tmpdir}/audio2.m4a"
+
+ extract_audio "${infile}" "${audio1}"
+ encode_audio "${audio1}" "${audio2}"
+ mux_replace_audio "${infile}" "${audio2}" "${outfile}"
}
continue
fi
+ tmpdir="$(mktemp -d "${TMPDIR:-/var/tmp}/pal-XXXXXXXX")"
convert_file "$infile" "$outfile"
+ rm -rf "$tmpdir"
done