[Livin]

I hope this helps some people. I'm pretty sure my setup and what I'm trying to achieve must be pretty common. I hope its not specific to my hardware.

I have 2 independent zones on my AV receiver. Zone 1 audio is 5.1 from my video card's HDMI port. Zone 2 can only receive analogue and is hooked up to a pair of outdoor stereo speakers. Zone 2 is only used for stereo music, not 5.1 video. The way I use it is if zone 2 is playing then, zone 1 is either muted or is playing the same thing as zone 2. I haven't tried playing something different on zones 1 and 2 using two instances of XBMC or another media program. I can't see why what I describe below wouldn't work for that, but then again I can't really work out why it does work in the first place. This would also work for anyone that wants simultaneous stereo headphones and 5.1 output.
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I've found I can get dual audio in Eden (I haven't tested Frodo yet, but it should work) without using the dual audio options if I plug my front (headphone) audio port into zone 2 using a 3.5mm to stereo RCA adapter cable and set headphones as the default output device in windows (it only shows up if something is plugged in), then go into to XBMC audio settings and set my video card's HDMI and 5.1 as the output device. I'm using WASPI (following the XBMC WASPI audio engine guide) and everything seems to work fine outputting simultaneous stereo to zone 1 and 2. Zone 1 outputs 5.1 surround for movies. For some reason if I unplug the headphone port, the sound on zone 1 becomes garbled, no idea why but I just leave it plugged in and everything is fine.

I'm not sure why this works (all my research tells me it shouldn't). It may be do with the fact that I'm using onboard sound and a separate video card, but I would have thought that was pretty common. My guess is its something to do with the way windows mutes speakers when you plug in headphones and XBMC is overriding it. Not sure if it would work with onboard HDMI video or in linux.

I use an Onkyo NR818 and would like to have 2 channel audio into Zone 2, while still having complete pass-through (for DTS, etc) on the HDMI output. I tried Virtual Audio Cable and it did not work... it would not pass both analog to the headphone jack while passing HDMI audio. I would get one or the other, not both at the same time.

my htpc is a laptop so not sure how the audio circuitry works... I'll try and post back.