I am running the same OS/Driver version as timdim (Realtek HD Audio Driver 18.104.22.16818 [R2.79], Windows 10 build 14393), where can I find the modified 2.75 version of RltkAPO64.dll?
You might be able to use Pihto's patch on the R2.79. He linked to it in the following post (I noticed that Google Chrome detects it as malicious, but it could just be a false positive):
Try to apply this patch to newest drivers. I made patch a long time ago, but it must to work properly till now.
I'm currently running unpatched Realtek HD Audio (ALC887) R2.79 drivers on Windows 10 64-bit, using optical out, and while regular Dolby Digital works, regular DTS does not. (I get no sound when testing DTS Audio in the Realtek Digital Output properties -> Supported Formats tab.) Is this still a bug as of Windows 10 Anniversary Update?