do you use 2 computer to do this ?
the graphiccard should be connected with "thunderbold" to the macpro you
want to output the signal.
now if you do so you need to select the output in modul8 "cmd" U (deselect cmd T)
this is the fullscreen mode .
now it should send the video to the blackmagic.
you also can select the kind of videosignal (720 p , 50 fps).
to do this you need a thunderboldt to "HDMI" .
I use the BM shuttle Extrem to do this.
Act without doing; work without effort. Think of the small as large and the few as many. Confront the difficult while it is still easy;
accomplish the great task by a series of small acts.