Video discs can have various signals on them. A feature may have a 1.0 mono track with messages or previews with 2.0 or 5.1 tracks.
Concert discs may contain a 2.0 track as well as multichannel Dolby, DTS or PCM tracks. If playing a 2.0 track in Pure Direct mode using a Yamaha receiver, there will be no signal output to the subwoofer. Switch to Straight mode and the 2.0 signal will be bass managed and the subwoofer will be active.