Embedded audio through display port Redhat 6.3

I have a HP Z820 workstation with an Nvidia Quadro 500 card running Redhat 6.3 as a desktop workstation. We are trying to get embedded audio out of the displayport to go into our AV system in a conference room. In the system prefs in Gnome gui we select HDMI as audio output but we get no sound to the AV/speakers.

We are trying to avoid using analog audio because the computer is connected to a KVM with a Windows and Mac system and everything else is digital embedded audio in the chain so it would take some reconfiguration of the entire room to switch to analog.

Is there anything in the config file that needs to be changed or any other tricks to make it work?