Vista - Surround Sound option Grayed out with HD4870 and HDMI connection

I just built an HTPC wiith Vista64 SP1 and am having a problem. I have a DFI LanParty X58-T3H6 motherboard and a VisionTek Radeon HD 4870 Video card with HD audio. I have an HDMI cable going to my Sony AV receiver and all I get is Stereo Audio. The subwoofer never comes out of standby nor does the AV receiver indicate anything but a stereo input.

I have the RealTek HDMI audio device installed and it says it is working properly under Device Manager. Under properties all that is offered is Stereo speakers. Surround Sound is shown as an option but it is grayed out and not selectable. All drivers are up to date as of two days ago, and I have the on-board sound of the motherboard disabled in its BIOS.

Other HDMI devices, such as my XBOX 360, do surround sound through the Sony AV receiver.

VisionTek support told me to install the HDMI RealTek driver, but that's all the help they've been able to give me.

If anyone has some additional insight on this, it would be most appreciated!

Thank you!

Honestly I think that HDMI can sometimes be flaky. I know you said the 360 works fine, but a PC is another animal entirely. I've Never used a HDMI connection to carry BOTH vid/sound FOR THE PC (will run HDMI for vid, but always run separate sound).

If your PC is close to the AV receiver.....A suggestion just to test is -- enable the MB sound and run a cable from the MB to your receiver (digital Optical [toslink] OR coax digital) if you have it, or you can do 3.5mm analog with a Y cable that is 3.5mm to RCA.

How To Connect Your PC to Your Home Stereo or Home Theater | Hardware Secrets

See if that works & then you know the bottleneck is the HDMI somehow & maybe drivers will fix it later, but for now you have (separate) sound that works.

Thanks for the suggestion, though I bought the 4870 specifically for it's ability ti use HDMI for audio/video. Previously I used a Radeon HD 2600 XT with HDMI and that worked fine.

I know I could use optical to carry the audio, but I recently bought the new recevier because it had enough ports for all my HDMI devices and let me get rid of a lot of cabling.

As a last resort I could certainly do this but I went with this particular card since ti was supposed to support audio/video over HDMI. The fact that Stereo works with it tells me something weird is going on as obviously some sound is being carried out the HDMI port.

Almost all the research I did online before posting here were cases where there was no sound at all from the HDMI output, just video.

Thanks again for taking the time to reply!

Have you actually installed the driver? You can find it here Realtek (you will have to accept the disclaimer before proceeding). The item you want is ATI HDMI Audio Device.

Yes, sorry if I was unclear about that. VisionTek tech support directed me there there, and I installed it, and it shows up as working properly.

Can you post some screenshots of the properties to illustrate what you mean? Please show all property pages of the device.

Sure, once I get home I will do that, and thanks much.

Pictures for the RealTek HDMI device and properties are attached

I fixed this last night.

My RealTek properties were only showing left and right speakers as was Vista's control panel. While I had previously uninstalled the VisionTek and RealTek drivers and then reinstalled them, which did not work, I did something different last night. I uninstalled both drivers, went to AMD's website and downloaded their version for the HD 4870. Not only did it fix my audio problem, but my 3DMark score went from 15,200 to 16,000! Thanks to those who offered suggestions, I appreciate it!