Hi,
It’s actually possible right now via DirectShow with our Windows driver. This means that developers writing custom applications can access more than one DeckLink card in a single system. Unfortunately, this is not supported in the NLEs out there in the market place so it still seems like only one card is supported.
It sounds like you’re rolling your own application. If you’re running into difficulties accessing more than one card, please write to me (support[at]blackmagic-design.com) and I’ll direct you to the relevant resources.
regards
Kristian Lam
Blackmagic Design