Hi Donald!
I have tested your new dgmvcsource.dll b26
But sorry, same behavior: First about 10 sec until it starts encoding, and then encodes black frames.
SW mode works.
I'm working with Dell 9560, W10 Pro and Avisynth 2.6.0 / Avisynth+
EDIT:
If I right remember I had the same problem with The Marsian 3D.