+function mux_replace_audio {
+ infile="$1"
+ audiofile="$2"
+ outfile="$3"
+
+ set -x
+ trackid="$(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="$1"
+
+ mpv \
+ --no-terminal \
+ --no-video \
+ --ao pcm:waveheader:file=/dev/stdout \
+ "$infile"
+}
+
+function slow_audio {
+ sox \
+ --temp "$tmpdir" \
+ /dev/stdin \
+ -t wav /dev/stdout \
+ speed "${SLOWDOWN}" \
+ gain -n \
+ channels 2
+}
+
+function encode_audio {
+ outfile="$1"
+ lame \
+ --preset standard \
+ /dev/stdin \
+ "${outfile}"
+}
+
+function convert_file {
+ set -xe
+ 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}" "${outfile}"
+
+ rm -rf "$tmpdir"
+}
+
+