Realtek has a cool driver that is simply named "ATI HDMI Audio Device". The driver is version R1.62 and dated 16th of March 2007. It is 15023k in size.

We opened the driver and found out that "HDMI Device WHQL Support: ATI HDMI Devices"

There is even more:

[AzaliaManufacturerID]

"ATI HDMI Audio" = RtAzAudModel, HDAUDIO\FUNC_01&VEN_1002&DEV_791A

"ATI HDMI Audio" = RtAzAudModel, HDAUDIO\FUNC_01&VEN_1002&DEV_793C

"ATI HDMI Audio" = RtAzAudModel, HDAUDIO\FUNC_01&VEN_1002&DEV_AA01

"ATI HDMI Audio" = RtAzAudModel, HDAUDIO\FUNC_01&VEN_1002&DEV_AA09

"ATI HDMI Audio" = RtAzAudModel, HDAUDIO\FUNC_01&VEN_1002&DEV_AA11

"ATI HDMI Audio" = RtAzAudModel, HDAUDIO\FUNC_01&VEN_1002&DEV_AA19

We only wonder is this graphics or motherboard stuff. Until it's taken down the driver is available here or here.