16:9 (compressed) mode is very useful for anyone who has a "progressive scan TV or projector" that CANNOT detect and switches between the 4:3 and 16:9 scenes automatically within a DVD.

DVD player with progressive scan plays at 16:9 (compressed) mode can detect and play 16:9 scenes in full theatre format and switches to TV format when 4:3 scenes are detected AUTOMATICALLY without any need to switch between the 2 formats manually.

Usaully, the TV/projector is set to the widescreen format.