This script removes all subtitles from a mkv file.

mkvsrtdel.sh

#!/bin/bash
################################################################
# This script removes all subtitles from a mkv file.           #
################################################################
usage="[i] Usage: `basename $0` video.mkv"

# Checking parameter
if [ -z "$1" ]; then
	echo ""; echo $usage; echo ""; exit
fi

# Setting up vars
mkvfile=$1

# Adding suffix in new filename
newmkvfolder=$(dirname "${mkvfile}")
filename="${mkvfile##*/}"
filename="${filename%.*}"
if [ ${filename: -3} == ".br" ]; then
	filename=${filename:0:${#filename}-3} # remove '.br' suffix
	echo "INFO: '.br' suffix removed."
fi
suffix="nosub" # to distinguish the old mkv from the new
newmkvfilename="${filename}.${suffix}.mkv" # gets the filename without the path
newmkv=$newmkvfilename # do the work on current directory

# Checking if mkv file has at least one subtitle
mkvmerge -i "$mkvfile" | grep 'subtitle'
if [ $? != 0 ]; then
	echo "INFO: There are no subtitles in this file already."
	mv "$mkvfile" "$newmkv"
	exit 0
else
	echo "INFO: Subtitles detected."
fi

# Building a new mkv container without subtitles and no video reencode (fast)
mkvmerge -S -o "$newmkv" "$mkvfile"  # -S => --no-subtitles # remove all subtitles
success=$?

# Cleaning original files
if [ $success == 0 ]; then
	echo "SUCCESS: Subtitle removed."
	rm "$mkvfile"
	echo "INFO: The original file was removed."
else
	echo "ERROR: A error ocurred. Be aware."
fi
exit 0