DVD Player & AV Receiver Help

Hello! this is my first post here, seems like a nice community. Hopefully someone here can help me with my question, it's been bothering me.

I just bought a new AV receiver (a Onkyo 7.1 surround sound) and am confused on how CD works through the system. I want to play my CD's through the DVD player. If I do this, can I get 7.1 sound through the CD? Because I have a Digital Coaxial Cable running through the DVD player to the AV receiver.

But the outcome sounded quite weird when I did that. The sound coming out of the speakers didn't sound right, maybe I was doing something wrong?

Then after that, I hooked an analog cable (white, red) from the DVD player to the AV receiver and again it sounded weird.

Supposedly this AV receiver is supposed to be really good with CD's.... can anyone help. Oh and if it helps the model of the AV receiver is "HT-S790".

Thanks for reading!