I was trying to play some demo 5.1 Surround Dolby on Youtube from my PC to my Yamaha RX-A770 via HDMI from a Sapphire Radeon NITRO R9 380 4GB GPU. The audio is coming in via the AMD True Audio from the GPU. Even though the source is Is Dolby DTS and my Yamaha can decode it all I get is 3.1 R/L, center, and Subwoofer. No surround R/L. Nothing 5.1 from Youtube via my Apple TV either. Is there a setting I am unaware of? Purchased movies on Apple TV, and Amazon no problem.