What you need to realize is that a button is simply an area that can be activated to do a specific action. It doesn't matter what is on the video.
The button can be invisible. The colors used for the various states that a button can have do not need to be seen. Using the method that Jon Geddes talked about above is probably the easiest way to put a button on a video.
I recommend you watch Andrew Kramer's tutorial about DVD authoring at
Video Copilot. He takes you through using After Effects to create the motion background (including the intro) and the buttons using the method Jon described.
Ken Knowles
Knowles-McNiff
