How to add permanent subtitle to mkv

[ybe]

hello,

I look for a program that add permanent subtitle to mkv(also unicode).
i will explain;

i want to convert mkv file+subtitle in hebrew to avchd, in order to see the movie in my blue-ray player.
i use avchdcoder but the subtitle outcome is gibrish.
i want hardcore subtitle in the mkv file , and then the convert will be only on the video file( the subtitle will be part of the file/picture).
to do this i need program the also can handle in unicoe(hebrew).


Thank you