-#!/bin/bash -e
+#!/bin/bash
-# Many DVDs released in Australia are sped up from 23.976fps to 25fps.
+# Many DVDs released in Australia are sped up from 24fps to 25fps.
# This script reverses the procedure, correcting the audio pitch.
-# Input files are assumed to be mkv files with track 2 audio.
-# The video framerate is adjusted without re-encoding. The audio is slowed and
-# 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.
+# - Chapters and subtitles are also adjusted to match the new timing.
-if [ -z "$1" -o -z "$2" ]; then
- echo "Usage: $0 destdir infile"
- exit 1
+if [ -z "$1" ] || [ -z "$2" ]; then
+ echo "Usage: $0 infile outfile"
+ exit 1
fi
-# FORCEFPS = 24000 / 1001
-# SLOWDOWN = FORCEFPS / 25
-FORCEFPS="23.976023976023978"
-SLOWDOWN="0.9590409590409591"
+set -o pipefail -eux
+OLDFPS="25"
+NEWFPS="24"
+SLOWFILTER=("-filter" "asetrate=46080,aresample=osr=48000:resampler=soxr")
-destdir="$1"
-infile="$2"
-outfile="$destdir/$(basename "$infile")"
-tmpdir="$(tempfile -p 'pal-')"
-rm "$tmpdir"
+function main {
+ local infile="$1"
+ local outfile="$2"
-if [ -f "$outfile" ]; then
- echo "Not overwriting $outfile"
- exit 0
-fi
+ local tmpdir=""
+ tmpdir="$(mktemp -d "${TMPDIR:-/var/tmp}/pal-XXXXXXXX")"
+ local audiofile="${tmpdir}/audiofile.m4a"
+
+ encode_audio "$infile" "$audiofile"
+ remux_file "$infile" "$audiofile" "$outfile"
+
+ rm -rf "$tmpdir"
+}
+
+function encode_audio {
+ ffmpeg \
+ -i "$1" \
+ -vn \
+ "${SLOWFILTER[@]}" \
+ -c:a libfdk_aac -vbr 3 \
+ "$2"
+}
+
+function remux_file {
+ local infile="$1"
+ local audiofile="$2"
+ local outfile="$3"
+
+ local audiodelay=""
+ audiodelay="$(get_minimum_timestamp "$infile" "audio")"
+
+ local videodelay=""
+ videodelay="$(get_minimum_timestamp "$infile" "video")"
+
+ local videotrackid=""
+ videotrackid="$(get_track_id "$infile" "video")"
+
+ local suboptions=()
+ local subtitletrackid=""
+ while read -r subtitletrackid; do
+ suboptions+=("--sync" "${subtitletrackid}:0,${OLDFPS}/${NEWFPS}")
+ done < <(get_track_id "$infile" "subtitles")
+
+ local chapteroptions=()
+ if [ "$(get_chapter_count "$infile")" -gt 0 ]; then
+ chapteroptions=("--chapter-sync" "0,${OLDFPS}/${NEWFPS}")
+ fi
+
+ mkvmerge \
+ -o "${outfile}" \
+ --default-duration "${videotrackid}:${NEWFPS}fps" \
+ --sync "${videotrackid}:$((videodelay / 1000000))" \
+ "${chapteroptions[@]}" \
+ "${suboptions[@]}" \
+ --no-audio "$infile" \
+ --sync "0:$((audiodelay / 1000000))" \
+ "$audiofile"
+}
+
+function get_track_id {
+ mkvmerge -i -F json "$1" | jq -r ".tracks[] | select(.type == \"$2\") | .id"
+}
-set -x
-mkdir "$tmpdir"
-mkvextract tracks "$infile" 2:"${tmpdir}/audio"
-mplayer -ao pcm:file="${tmpdir}/audio.wav" -vo null "${tmpdir}/audio"
-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"
+function get_minimum_timestamp {
+ mkvmerge -i -F json "$1" | jq -r ".tracks[] | select(.type == \"$2\") | .properties.minimum_timestamp"
+}
-rm -rf "$tmpdir"
+function get_chapter_count {
+ mkvmerge -i -F json "$1" | jq -r ".chapters | length"
+}
+main "$@"