I'm wondering if there's any possibility to upmix stereo sound to 5.1 when using HDMI. I have my AVR connected to my 7970 and Windows is set up to use 5 speakers plus LFE. So my AVR is receiving a six channel sound stream. Unfortunately, if an application only uses stereo sound, the AVR only receives data on two channels ... but the link is still established for six channels.
I know that dedicated sound cards or onboard ALC-codecs are able to upmix this kind of sound in order to have fake surround sound.
Switching Windows to stereo output isn't an option for me because I also watch DTS encoded movies (which works really fine).