Here are ways to improve iDVD performance:
Consider resizing large, high-resolution slideshow images to 720 x 480 pixels for standard projects and 854 x 480 pixels for widescreen before you add them to your project.
Large images can slow iDVD performance. (The performance of your burned DVD is unaffected by image size.)
Make sure motion is turned off while you’re working on your project if your project has complex dynamic drop zones or motion menus. To turn motion on or off, click the Motion button (shown below).
Turn off background encoding if you are using the Best Performance encoding setting. To turn it off, choose Advanced > “Encode in Background.”
The checkmark is removed to show it’s no longer selected.