I assure you these are all (relatively) new releases which clearly state 5.1 capable. I also check the audio options and set for 5.1 My DVD player has 3 audio options: "Bitsteam" or "PCM" (manual says to use bitstream if using digital out) (I am) A DTS setting (my receiver has none) lastly...
I have a couple concert DVDs which I cannot get the 5.1 surround audio to work. For example: If I insert my Blackmore's Night DVD, my receiver automatically goes into Digital Dolby mode and I hear all 5 speakers playing. But if I try my Roger Waters (in the flesh) DVD, all I can get is 2-speaker...