Yes, HDMI carries video and DIGITAL audio.
The Onkyo TX-SR576 decode only up to DD-Pro.
Not TrueHD an DTS-HD.
For HD sound I have to use the analog outputs of the X-Fi.
The solution for the AV Receiver Problem:
Apparently I can only use the button "DVD".
Set HDMI2 to "DVD" button, then press...