Is VDR currently set up to pass through surround sound (SPDIF)?
I never get anything other than stereo - although I know some of the transmissions (esp the HD AC3 ones) must have multichannel. I get full 5.1 from DVDs and some BT downloads, just not from VDR watching TV. I have played with the sound options in xineliboutput and cranked it up from the default Stereo 2.0 to 5.1, choosen upmix, disabled downmix and it doesn't seem to do anything.
Interestingly, on the few occasions I have used VDR to record TV, I seem to have hit some transmissions that have more than 2 channels and it seems to play them fine, just not for live TV....