Hello all, Short answer to your question, Yes!
As long as you use a Decklink Card, although not every single model is known to work…USB3 and thunderbolt cards are not your best choice… PCIe cards are more reliable, although you may have to fidle with the settings, as the internal framebuffers for each card are different… there is a setting for that in the API.
Also you have to know your way around glsl as these cards usually work in modes other than RGB, so you must convert YUV422 (10 or 8 bit) to RGB and flip the image upsidedown before using it…
You must also consider how to take the composed image back to video (also supported by UpBGE), as you will then require at least a Decklink Duo to have input and output.
If you use Windows, then you will benefit from using a Quadro Card for compositing, as the Decklink module takes advantage of GPU Direct (from Nvidia Quadro Drivers Only) to have direct access to the aquired image on the GPU. Be sure to have dvp.dll along side with UpBGE…
Hope that helps!
Happy new year!