depends on what youre using the vids for, but if youre just putting them to youtube or something they say to use "MPEG4 (Divx, Xvid) format at 320x240 resolution with MP3 audio". i usually just use mpeg2 to make them smaller when theyre just for myself but i think thats mainly because its like the first selection on my video software. ive not used virtual dub though so i cant assist with that aspect.