I have several DVDs which claim to be encoded as Dolby Digital which, when played on a SONY 550 through the AVR-3300 display as Dolby Pro Logic. Others which claim to be encoded in Dolby digital correctly display as Dolby Digital on the AVR-3300 display. In all cases the Dolby Digital LED comes on but for some DVDs the display says Dolby Pro Logic. Does anyone know what is going on?