DRM problems Big Sur opencore 0.6.7 boot

Hi all. I need some help. I have a working Big Sur install but I can’t play any DRM protected video using the Apple TV app or Netflix. My rig is an old ASUS P7P55 LX with an i7 860 16 gig DDR3 and a Nvidia GT640.

I have tried adding Shikigva=256 to the boot args but this has no effect. I have run VDADecoderChecker and it is showing an error 12473

Any help would be welcome.

Author: @Consistent-Cut-6290