videoDECKLINK plugin is not able to detect pixel format
it seems that Gem is not able to properly detect RGB format of HDMI input. if i set my HDMI input signal to YCbCr444 it works, but if i use RGB format it doesnt.
seems like i'm too dumb to set my video-output to anything but RGB.

on my GTX 660ti the option was not greyed out and had multiple options, so its not about you being dumb. but i tested with raspberry pi, which is also capable of various formats. i will test again.
well...
one funny thing is, that for me, the format is obviously RGB, so that is the only format that I can test and which does work as expected.
unless the nvidia-settings are lying.
the videoDECKLINK plugin still defaults to "8Bit YUV" internally (which aligns better with your YCbCr444), so there appears that some format conversion is happening somewhere.
now here comes the fun part:
if i use the new (as of 774b8d6) pixformat property, it works with both yuv8 (8bit YUV, the default; since ever)) and yuv10.
But if I choose argb8 or bgra8, the grabbing simply "freezes" (frames are not updated), until I switch back to one of the YUV formats.
@kubriel : is this similar to what you are seeing?
@umlaeute i dont remeber. will try to test it soon.