Lg soundbar to asus z170 pro gaming mobo

[brandy12345]

hi I have been trying to connect my lg sound bar to my z170 motherboard via optical cable but upon playing games all I'm getting is pcm,
My sound bar supports Dolby/dts and I've tried reinstalling Realtek drivers etc but still outputting pcm via in game (yes I've looked at in game settings)
So basically I've connected my hdmi lead from my 1080ti to to and z170 optical output to lg sound bar optical,
If it helps I'm on windows 10

 

[EsaT]

Getting 5.1 out through optical needs DD/DTS encoding from sound card.
(not because of lack of optical fiber's bandwidth but because of old standard)
Something not included with Realtek normally.

Anyway stereo doesn't need any compression and works with standard PCM.

 

[brandy12345]

So how can I get Dolby/dts through my sound bar from the motherboard via optical ?
Or is it impossible and need a dedicated sound card