@Sniki,
Sorry for the delay in DRM testing.
I prepared the following chart for Opencore 0.6.3 and Catalina 10.15.7. For an
AMD DGPU, it seems to make little difference in the shikigva settings, whether
the SMBIOS is iMacPro1,1 or MacPro6,1 for AppleTV decoding. Although I assumed
that the iMacPro1,1 would not need the shikigva flag in bit 4 (i.e 16 in the sum)
both IMP11 and MP61 need it for full AppleTV functionality, and the best setting
is shikigva=144 (128+16) for AppleTV. With Big Sur, both MP61 and IMP11 are
mostly dysfunctional, and mostly regardless of shikigva setting, one can first
download and then play media content in m4v content, but one cannot play HLS
video in any form and one cannot stream HLS or mv4.
With Opencore 0.6.3 and Catalina 10.15.7 with an Nvidia, it works mostly for
AppleTV with shikigva=288 and an appropriate shiki-id setting. 288=256+32.
The 256 tells it to use software decoding and the 32 tells it to substitute a
different board-id for video. I've successfully used Nvidia shiki-id's as indicated
by Dortania's OpenCore SMBIOS page, such as shiki-id=Mac-FC02E91DDD3FA6A4
(emulating iMac13,2) and shiki-id=Mac-2BD1B31983FE1663 (emulating MacBookPro11,3)
with the SMBIOS set to MP6,1. It may only successfully stream AppleTV (HLS and 4v)
and not work with Quicktime or downloaded media.
With Opencore 0.6.3 and Big Sur, MP61 and IMP11 seem to mostly assume that the
IGPU is off. I've had some luck with Big Sur SMBIOS set to iMac18,3 and a fully featured
IGPU enabled with AAPL,ig-platform-id set to <0A006601>. AppleTV still fails,
but Hackintool reports VDA Decoder fully supported, VideoProc reports 4K in H264
and HEVC, and Sony's Swordsmith and Food Fizzle play smoothly.
The last two screen captures are from the iMac18,3 SMBIOS with an RX560 and IGPU
enabled. The first shows an oral Siri inquiry. You can see from Intel Power Gadget
that the IGPU is enabled, and throttles up as Siri processes. Without the IGPU enabled,
Siri takes a little longer to start up. The second shows LuxMark 3.1 running a stress
test with the IGPU enabled. You can see the HD4000 graphics fully throttled up.
I'm using AGPMInjector with some changed values for the IGPU and Nvidia AGPM.
I'm attaching a zip of the experimental info.plist.