It looks like I solved it.
The situation was like this: I am using an Intel NUC with a fresh Win10x64 installation and latest Xibo CMS with a latest Xibo player. K-Lite codecs and VLC were installed, WMP was able to play everything.
Usually when setting up brand new computers, Win10 has most drivers out-of-the box or they later come with an update. In this case the device manager shown that the gfx driver was in fact an Intel HD graphics one, but supplied by Windows.
Problem was that when a video is to be shown, only an audio wave would appear and you could hear the audio, but there's no video.
I tried all of the solutions, none worked, but then the last thing I tried was to update video drivers to latest from the Intel website. And that worked ok.
TL;DR don't trust MS's drivers, use official drivers.