-#!/bin/bash -e
+#!/bin/bash
# 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 ...]"
+ echo "Usage: $0 infile outfile"
exit 1
fi
-set -xe
+set -o pipefail -eux
FORCEFPS="24"
-SLOWDOWN="0.96"
+SLOWFILTER="-filter asetrate=46080,aresample=osr=48000:resampler=soxr"
function mux_replace_audio {
- infile="$1"
- audiofile="$2"
- outfile="$3"
-
- trackid="$(mkvmerge -i "$infile" | grep video | sed 's/^Track ID \(.\):.*$/\1/')"
- exec mkvmerge -o "${outfile}" --default-duration "${trackid}:${FORCEFPS}fps" --no-audio "$infile" "$audiofile"
+ local infile="$1"
+ local audiofile="$2"
+ local outfile="$3"
+
+ local audiodelay="$(get_minimum_timestamp "$infile" "audio")"
+ local videodelay="$(get_minimum_timestamp "$infile" "video")"
+ local videotrackid="$(get_track_id "$infile" "video")"
+
+ mkvmerge \
+ -o "${outfile}" \
+ --default-duration "${videotrackid}:${FORCEFPS}fps" \
+ --sync "${videotrackid}:$((videodelay / 1000000))" \
+ --no-audio "$infile" \
+ --sync "0:$((audiodelay / 1000000))" \
+ "$audiofile"
}
-function extract_audio {
- infile="$1"
-
- exec mpv \
- --no-terminal \
- --no-video \
- --ao pcm:waveheader:file=/dev/stdout \
- "$infile"
+function get_track_id {
+ mkvmerge -i -F json "$1" | jq -r ".tracks[] | select(.type == \"$2\") | .id"
}
-function slow_audio {
- exec sox \
- --temp "$tmpdir" \
- - \
- -t wav - \
- speed "${SLOWDOWN}" \
- gain -n \
- channels 2
+function get_minimum_timestamp {
+ mkvmerge -F json -i "$1" | jq -r ".tracks[] | select(.type == \"$2\") | .properties.minimum_timestamp"
}
function encode_audio {
- outfile="$1"
- exec lame \
- --preset standard \
- - \
- "${outfile}"
+ ffmpeg \
+ -i "$1" \
+ -vn \
+ $SLOWFILTER \
+ -c:a libfdk_aac -vbr 3 \
+ "$2"
}
function convert_file {
- infile="$1"
- outfile="$2"
- tmpdir="$(mktemp -d "${TMPDIR:-/var/tmp}/pal-XXXXXXXX")"
- audiofile="${tmpdir}/audio.mp3"
+ local infile="$1"
+ local outfile="$2"
+ local audiofile="${tmpdir}/audiofile.m4a"
- extract_audio "${infile}" | slow_audio | encode_audio "${audiofile}"
- mux_replace_audio "${infile}" "${audiofile}" "${outfile}"
-
- rm -rf "$tmpdir"
+ 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 $outfile"
- continue
- fi
-
- convert_file "$infile" "$outfile"
-done
-
+infile="$1"
+outfile="$2"
+tmpdir="$(mktemp -d "${TMPDIR:-/var/tmp}/pal-XXXXXXXX")"
+convert_file "$infile" "$outfile"
+rm -rf "$tmpdir"