When using the latest Intel drivers for Intel HD Graphics and Intel Display Audio for the Celeron 2955U on Windows 8.1 64-bit causes HDMI audio output to be broken.
Using default class drivers, HDMI audio output constantly displays that no output is connected in "Playback Devices". After installing the Intel specific drivers, no output devices are shown at all in the "Playback Devices" dialog box.
There are no errors when installing the drivers, and the Display Audio Out is reported as functioning normally within device manager. Further, HDMI output functions correctly under a Linux install with Intel drivers. This leads me to believe this is a device- and OS-specific driver issue that can be resolved by a driver update from Intel.
I am not the only one experiencing this issue. For more information, please review the posts here and here
Please let me know if you need any information from me (such as system logs, etc.) to help with debugging and resolving this issue on Windows.