I no longer have issues with HD Audio Bitstreams. Its been a while but it was resolved by either a BIOS update or an Intel Display Audio Driver--I believe it was the Display Audio driver. I am using BIOS 0026 and Gfx drivers:
10.18.10.3643
(Latest)
http://downloadmirror.intel.com/23926/eng/WY_0026_ReleaseNotes.pdf