Buttons in menu (with a photo or a film) are not sharp

I've made buttons in the menu of a dvd. With preview, all the buttons (with a photo or a video) looks good and are sharp.
But after burning a dvd, the buttons on the dvd aren't sharp. ( the main films are sharp).
The film from the buttons are selected pieces from the main films, or photo's.

IT looks like a rendering issue, but in dvd sp, you can't set the rendering quality for the buttons I mean.

The films are ProRes 422 converted in Compressor to dvd SD. Source and destination both in 16:9.

So what to do for looking good buttons?