There's another problem with 640x480 on SD TVs. If it has hard subtitles, and they are placed low enough in the frame, they'll be cut off on a regular TV set (because of so-called "
overscan"). Shrinking the video doesn't solve this problem (at least it didn't for me). You have to add the black bars that NSW describes in the linked post. I believe GHDpro's scripts handle that problem for Windows users. With mencoder on Linux I've used
this technique.