-#!/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
-# volume 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.
if [ -z "$1" -o -z "$2" ]; then
- echo "Usage: $0 destdir infile [infile ...]"
+ echo "Usage: $0 infile outfile"
exit 1
fi
+set -o pipefail -eux
FORCEFPS="24"
-SLOWDOWN="0.96"
+SLOWFILTER="-filter asetrate=46080,aresample=osr=48000:resampler=soxr"
-destdir="$1"
-shift
+function mux_replace_audio {
+ local infile="$1"
+ local audiofile="$2"
+ local outfile="$3"
-for infile in "$@"; do
- outfile="$destdir/$(basename "$infile")"
+ local audiodelay="$(get_minimum_timestamp "$infile" "audio")"
+ local videodelay="$(get_minimum_timestamp "$infile" "video")"
+ local videotrackid="$(get_track_id "$infile" "video")"
- if [ -f "$outfile" ]; then
- echo "Not overwriting $outfile"
- continue
- fi
+ mkvmerge \
+ -o "${outfile}" \
+ --default-duration "${videotrackid}:${FORCEFPS}fps" \
+ --sync "${videotrackid}:$((videodelay / 1000000))" \
+ --no-audio "$infile" \
+ --sync "0:$((audiodelay / 1000000))" \
+ "$audiofile"
+}
- set -x
- tmpdir="$(mktemp -d "${TMPDIR:-/var/tmp}/pal-XXXXXXXX")"
- mplayer -novideo -ao pcm:file="${tmpdir}/audio.wav" -vo null "$infile"
- sox "${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_track_id {
+ mkvmerge -i -F json "$1" | jq -r ".tracks[] | select(.type == \"$2\") | .id"
+}
- rm -rf "$tmpdir"
-done
+function get_minimum_timestamp {
+ mkvmerge -F json -i "$1" | jq -r ".tracks[] | select(.type == \"$2\") | .properties.minimum_timestamp"
+}
+function encode_audio {
+ ffmpeg \
+ -i "$1" \
+ -vn \
+ $SLOWFILTER \
+ -c:a libfdk_aac -vbr 3 \
+ "$2"
+}
+
+function convert_file {
+ local infile="$1"
+ local outfile="$2"
+ local audiofile="${tmpdir}/audiofile.m4a"
+
+ encode_audio "$infile" "$audiofile"
+ mux_replace_audio "$infile" "$audiofile" "$outfile"
+}
+
+
+infile="$1"
+outfile="$2"
+tmpdir="$(mktemp -d "${TMPDIR:-/var/tmp}/pal-XXXXXXXX")"
+convert_file "$infile" "$outfile"
+rm -rf "$tmpdir"