Hiya!

Not an answer to your question but it's an easy way of playing MKV files on your PS3, assuming you have it connected to the same network as your computer.

PS3 Media server
After installing the program you should be able to find your pc's media server on your PS3 and browse through all the shared files, it handles MKV and pretty much every format your PC plays. Works very good, even for 1080p files