-#!/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, and encoded as AAC, preserving surround sound.
+# - 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
+if [ -z "$1" ] || [ -z "$2" ]; then
echo "Usage: $0 infile outfile"
exit 1
fi
-set -xe
-FORCEFPS="24"
-SLOWFILTER="-filter asetrate=46080,aresample=osr=48000:resampler=soxr"
+set -o pipefail -eux
+OLDFPS="25"
+NEWFPS="24"
+SLOWFILTER=("-filter" "asetrate=46080,aresample=osr=48000:resampler=soxr")
-function mux_replace_audio {
+function main {
local infile="$1"
- local audiofile="$2"
- local outfile="$3"
-
- local audiodelay="$(get_audio_delay "$infile")"
- local videotrackid="$(get_video_trackid "$infile")"
+ local outfile="$2"
- mkvmerge \
- -o "${outfile}" \
- --default-duration "${videotrackid}:${FORCEFPS}fps" \
- --no-audio "$infile" \
- --sync "0:$((audiodelay / 1000000))" \
- "$audiofile"
-}
+ local tmpdir=""
+ tmpdir="$(mktemp -d "${TMPDIR:-/var/tmp}/pal-XXXXXXXX")"
+ local audiofile="${tmpdir}/audiofile.m4a"
-function get_video_trackid {
- mkvmerge -i "$1" | sed -n 's/Track ID \([0-9]*\): .*video.*/\1/p'
-}
+ encode_audio "$infile" "$audiofile"
+ remux_file "$infile" "$audiofile" "$outfile"
-function get_audio_delay {
- mkvmerge -F json -i "$1" | \
- jq -r '.tracks[] | select(.type == "audio") | .properties.minimum_timestamp'
+ rm -rf "$tmpdir"
}
function encode_audio {
ffmpeg \
-i "$1" \
-vn \
- $SLOWFILTER \
+ "${SLOWFILTER[@]}" \
-c:a libfdk_aac -vbr 3 \
"$2"
}
-function convert_file {
+function remux_file {
local infile="$1"
- local outfile="$2"
- local audiofile="${tmpdir}/audiofile.m4a"
+ local audiofile="$2"
+ local outfile="$3"
- encode_audio "$infile" "$audiofile"
- mux_replace_audio "$infile" "$audiofile" "$outfile"
+ 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"
+}
+
+function get_minimum_timestamp {
+ mkvmerge -i -F json "$1" | jq -r ".tracks[] | select(.type == \"$2\") | .properties.minimum_timestamp"
}
+function get_chapter_count {
+ mkvmerge -i -F json "$1" | jq -r ".chapters | length"
+}
-infile="$1"
-outfile="$2"
-tmpdir="$(mktemp -d "${TMPDIR:-/var/tmp}/pal-XXXXXXXX")"
-convert_file "$infile" "$outfile"
-rm -rf "$tmpdir"
+main "$@"