2 for VCD, SVCD, or PAL DVD; ac3 is most commonly used for DVD. PCM audio may also be used for DVD, but this is mostly a big waste of space... r VCD; mpeg2video for SVCD; mpeg2video is usually used for DVD but you may also use mpeg1video for CIF resolutions.
* keyint: Used to set the GOP size. 18 for 30fps material, or 15 for... 9800 for DVD. For SVCD and DVD, you might wish to use lower values depending on your own personal prefe