Reformat a bunch of mkv files to 4:3 without transcoding.

reformat.sh

#!/bin/bash

# Directory containing the media files
media_dir="/path/to/media/files"
output_dir="/path/to/output/dir"

cd "$media_dir" || exit


for i in *.mkv
do
    if test -f "$i"
    then
        cleaned_name=$(echo "$i" | sed -e 's/[^A-Za-z0-9]/./g' | sed 's/\.\{2,\}/./g')
       ffmpeg -i "$i" -aspect 720:540 -c copy "$output_dir$cleaned_name"
    fi
done