High-def cable signal no longer Dolby Digital, now PCM

My Onkyo 5.1 reciever has always automatically interpreted and displayed Dolby Digital or DTS signals when sent from both my high-def cable box and Blue-Ray player. I leave the receiver set on Direct and it displays whatever is being sent. The Blue Ray player still works fine. But now the Time Warner Dolby Digital 5.1 programs via my high-Def DVR box being watched no longer display Dolby Digital on the receiver, the receiver display now shows in small letters PCM and it sounds poor. I've played with all settings with no luck. No video is passed thru the reciever, only audio via an Optical cable.

May have solved the problem myself last night. Cable box audio output was set to HDMI instead of Dolby Digital.