yamaha rx-v665

I own the v661 and for me to do what you are asking is push the Surround Decode button. See if that works.

If you have your DVD player's digital output set to "bitstream" and you are running coaxial or optical from DVD player to receiver, your receiver display should show Dolby Digital. If you are using the analog outputs to connect to a multi-channel analog input on the receiver, then you won't see anything on the receiver display, except maybe it will say "analog".