Allow me to give you a better idea. Connect the laptop to your TV using a D-Sub connector (if it's an digital LCD TV) or by using a VGA2Video converter (you can buy one for like 50$). That way you can keep using the high quality .mkv and still be able to use your TV.
What you are trying to do right now is kind of counter productive. You don't want to watch a 720p, for example, on your laptop, so you are looking for a 480p to watch on your TV. Now, your TV is larger then your laptop monitor, so you are looking for something of a smaller resolution to watch on a larger screen. That is not good.
Considering you have a PS3, your TV most likely has a D-SUB connector as well, so just buy a D-SUB cable, and connect your laptop to your TV. Don't forget to thank me later.