Suffice it to write that it's well discussed and some folk do not want to read about HDCP rules about pass through of HD audio and how what can work is thwarted by the rules. I will not offer much about this because of the tar pit and HDCP.
But it's not expected to work (5.1 pass through) with the fine exception of OTA.
I plug in a usb flash drive which has mkv video files with 5.1 audio but unfortunately the home cinema plays just 2.1 audio. I've already ran the mkv files with MediaInfo to be sure they are encoded with 5.1 audio. The MediaInfo report shows 6 channel sound.
What is the problem?