At the moment, the Vero 4k can only open 2 or 8 audio sinks to output PCM audio via HDMI. So, stereo will be ouput as 2 channel PCM, but every PCM audio file with more than 2 channels will be ouput as 8 channel PCM via HDMI. The remaining channels that are not filled by information from the played audio file (e.g. with a 5.1 PCM audio file - ergo 6 PCM channels - there are 2 channels left to be filled for 8 channels to be output) will be filled with blank channels containing no audio information.
See the attached image as well:
This is, of course, not awesome for dedicated 7.1 setups where the AVR can’t upmix 5.1 to 7.1 because it thinks there’s already a 7.1 signal coming in - which obviously contains 2 blanks channels. But the AVR can’t and won’t know that. So, especially setups which do upmixing of some sorts (to 7.1 dedicated speaker channels or 3D audio setups using 3D upmixers like DTS Neural:X e.g.) are affected negatively by this…
The whole issue - including all the implications for whatever scenarios are out there - has been discussed in the context of some PCM channel mapping not working before (which is fixed now), but Sam couldn’t raise much hope of this being changed any time soon.
But @ac16161, others - including me - have been asking for this, too. It’s something that has been asked for before and Sam is aware of it, I think. Maybe we’ll see some changes some day.