I'm new to encoding Divx files and need some help. I need to encode several different file sizes so that they fill an entire 4:3 television screen.

384x284 and
576x432

When I tried to play the 384x284 sized file, it showed up on the tv screen as a small square in the center of the screen. What size, or other things, do I have to make the file to make it fill the entire tv screen ? 16:9 (640x368....or about that) files seem to play just fine and take up the full width of the television screen. If it helps, I use ffmpegX 0.0.9u. Thanks.