+SLOWFILTER="-filter asetrate=46080,aresample=osr=48000:resampler=soxr"
+
+function mux_replace_audio {
+ local infile="$1"
+ local audiofile="$2"
+ local outfile="$3"
+
+ local trackid="$(mkvmerge -i "$infile" | grep 'Track ID.*video' | sed 's/^Track ID \(.\):.*$/\1/')"
+ mkvmerge -o "${outfile}" --default-duration "${trackid}:${FORCEFPS}fps" --no-audio "$infile" "$audiofile"
+}
+
+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}"
+}
+