Simple tool to strip all languages except the desired one from a mkv file

convert-lang-mkv.sh

#!/bin/sh

# Copyright (C) 2022  Dinko Korunic

# Simple tool to strip all languages except the desired one from a bunch of mkv files in a current folder
# Depends: mkvtoolnix

LANG_CODE="hr"

LANG_TRACK_COUNT=$(mkvinfo -s "$1" | head -50 | grep -c '^Track .*: audio')

if [ "${LANG_TRACK_COUNT}" -eq 0 ]; then
    echo "Unable to find any language track"
    exit 1
fi

if [ "${LANG_TRACK_COUNT}" -eq 1 ]; then
    echo "There is only a single language, no need to convert"
    exit 1
fi

LANG_TRACK=$(mkvinfo -s "$1" | head -10 | grep "^Track .*: audio.*language: ${LANG_CODE}" | grep -oP '(?<=track ID: )\d+')

if [ -z "${LANG_TRACK}" ]; then
    echo "Unable to find ${LANG_CODE} language"
    exit 1
fi

mkvmerge -o tmp.mkv --audio-tracks "${LANG_TRACK}" "$1" && mv tmp.mkv "$1"
rm -f tmp.mkv