I know, old thread. I'm just adding an out of the box thinking option for extenders, in case someone has a newer TV, doesn't want or cant find software changes/additions to add subtitles, or just needs them once.
Newer TV's allow auto captions when sound is muted.
I am running echo's with optical sound into soundbar/surround.
If I MUTE my tv speaker, I get captions on screen. I still have sound from my soundbar.
It actually works if I mute the echo or the sounbar as well..... but then you'd not have any sound to go with your subtitles.
Not as good looking as built in subtitles, but for a minimalist, one time, or once in a great while approach, it will work for tv. IF, you have a newer tv with the option. I haven't tried it with ripped movies, but from my understanding of the function, it should work.