Batch edit the properties of Matroska files.

mkv_fixer.sh

#!/bin/bash
#
# Iterate through every .MKV file in the current directory and use the 
# filename base as the title while assigning the second subtitle track 
# as the default and the second audio track as the default. 
# 
# Requires mkvpropedit from MKVToolNix: 
# https://github.com/mbunkus/mkvtoolnix
#
for file in *.mkv; do base=${file%.*}; mkvpropedit "${file}" --edit info --set "title=${base}" --edit track:s1 --set flag-default=0 --edit track:s2 --set flag-default=1 --edit track:a1 --set flag-default=0 --edit track:a2 --set flag-default=1; done