That depends on what you are using to burn the DVD. There is a DivX encoder available for Mac, so if you wanted to you could do that. But why would anyone want to use DivX, when there are better (official standard) solutions like MPEG-4 H2.64/AAC available on Mac right out of the box? If you use iDVD to burn a movie DVD, then of course it's a "proper" DVD (MPEG-2).