Setting up 2010 Macbook Pro Core i7 with Multichannel Audio via MDP-->HDMI

i have 17" 2010 macbook pro mini displayport allows both audio , video, , i've set connect via hdmi dynex hdtv, has optical audio connection panasonic 7.1 surround sound system. tv works fine 7.1 audio on else, , i've gotten video , 2-channel audio work on surround sound, can't set more stereo. seems software roadblock in audio midi setup (screenshot below). suggestions?

2010 mbp-->mdp-->hdmi-->hdtv-->optical audio-->7.1 surround receiver

 

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