Connecting my MacBook Pro (early 2011) to my Sony LCD TV (KDL-46XBR6) and listening to Multichannel surround sound.

Dear all,

I am attempting to connect my MacBook Pro (early 2011) to my Sony LCD TV (KDL-46XBR6) via the Mini DisplayPort to HDMI. I have successfully connected the two devices and can select "SONY TV XV" in the sound preference pane. I can see and hear what I'd like, however, I can only monitor the sound in 2 channel stereo. I have my TV connected to a Sony 7.1 audio receiver via an optical cable and can monitor 7.1 sound via other sources (Blu-ray, broadcast, etc). When I go into the Audio Midi Setup utility, I am unable to configure my speakers to be anything but 2 channel stereo. I am given the options for "2ch-16bit", "2ch-20bit", "2ch-24bit" and "Encoded Digital Audio". When I select "Encoded Digital Audio", my output automatically changes to Built-in Output. Has anyone been able to successfully resolve this issue? Thanks for all your help!

Gregg