Intel HDMI audio, only stereo

Hi.

I’m having troubles with getting more than stereo sound through my HDMI on my Intel NUC5i3RYH.
OS is Windows 10 x64, with all the latest updates, and drivers from Intel.

I’m using a HDMI splitter to get the audio from the HDMI, to my Logitech Z-5500.

In control panel>sound i can see it it recognizes my TV, but i can’t get more than stereo sound.

(My Windows is Danish, can change it to english if that helps)

I also tried ignoring this, and just setting the correct audio in Kodi, but everything comes out in Stereo, and DTS will not be played.

I was running Kodi in ubuntu on this system before, but during a update it went to shit, and i went ahead and installed Windows instead.
This was working as intended with Linux, with correct audio, so it must be a software issue.

I hope someone can help, I can’t think of anything i haven’t tried.

Best regards!