-#!/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.
+# - 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 [infile ...]"
+if [ -z "$1" ] || [ -z "$2" ]; then
+ echo "Usage: $0 infile outfile"
exit 1
fi
-set -xe
-FORCEFPS="24"
-SLOWDOWN="0.96"
+set -o pipefail -eux
+OLDFPS="25"
+NEWFPS="24"
+SLOWFILTER=("-filter" "asetrate=46080,aresample=osr=48000:resampler=soxr")
-function mux_replace_audio {
- infile="$1"
- audiofile="$2"
- outfile="$3"
+function main {
+ local infile="$1"
+ local outfile="$2"
- trackid="$(mkvmerge -i "$infile" | grep video | sed 's/^Track ID \(.\):.*$/\1/')"
- mkvmerge -o "${outfile}" --default-duration "${trackid}:${FORCEFPS}fps" --no-audio "$infile" "$audiofile"
-}
-
-function extract_audio {
- infile="$1"
+ local tmpdir=""
+ tmpdir="$(mktemp -d "${TMPDIR:-/var/tmp}/pal-XXXXXXXX")"
+ local audiofile="${tmpdir}/audiofile.m4a"
- exec mpv \
- --no-terminal \
- --no-video \
- --ao pcm:waveheader:file=/dev/stdout \
- "$infile"
-}
+ encode_audio "$infile" "$audiofile"
+ remux_file "$infile" "$audiofile" "$outfile"
-function slow_audio {
- exec sox \
- --temp "$tmpdir" \
- - \
- -t wav - \
- speed "${SLOWDOWN}" \
- gain -n \
- channels 2
+ rm -rf "$tmpdir"
}
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"
-
- extract_audio "${infile}" | slow_audio | encode_audio "${audiofile}"
- mux_replace_audio "${infile}" "${audiofile}" "${outfile}"
+function remux_file {
+ local infile="$1"
+ local audiofile="$2"
+ local outfile="$3"
- rm -rf "$tmpdir"
-}
+ local audiodelay=""
+ audiodelay="$(get_minimum_timestamp "$infile" "audio")"
+ local videodelay=""
+ videodelay="$(get_minimum_timestamp "$infile" "video")"
-destdir="$1"
-shift
+ local videotrackid=""
+ videotrackid="$(get_track_id "$infile" "video")"
-for infile in "$@"; do
- outfile="$destdir/$(basename "$infile")"
+ local suboptions=()
+ local subtitletrackid=""
+ while read -r subtitletrackid; do
+ suboptions+=("--sync" "${subtitletrackid}:0,${OLDFPS}/${NEWFPS}")
+ done < <(get_track_id "$infile" "subtitles")
- if [ -f "$outfile" ]; then
- echo "Not overwriting $outfile"
- continue
+ local chapteroptions=()
+ if [ "$(get_chapter_count "$infile")" -gt 0 ]; then
+ chapteroptions=("--chapter-sync" "0,${OLDFPS}/${NEWFPS}")
fi
- convert_file "$infile" "$outfile"
-done
+ mkvmerge \
+ -o "${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 "$1" | jq -r ".chapters | length"
+}
+main "$@"