#!/bin/bash
mkdir -p output
for a in *.mkv; do
    mkvmerge -o "output/${a%.mkv}.mkv" \
    --audio-tracks 2 \
    --subtitle-tracks 4 \
    --default-track 2 \
    --default-track 4 \
    --forced-track 1:0 \
    --forced-track 2:0 \
    --forced-track 3:0 \
    --forced-track 4:0 \
    "$a"
done