Black-bar detection automatically excludes the letterboxsing (i.e. black bars) along the edges of the vdeio from syncing. This means, when you're watching a widescreen video and the top side of the screen is black, the sync box will detect further inner part of the screen and make lights sync to the that area.
Black-bar detection Off:
This feature is by default turned on. If you do not want the letterboxing, or the black bars excluded from syncing, you can scroll down in the video sync page and turn off the Black-bar detection.