Fill & key with BMD output

Hi guys, any idea how to implement fill and key (luma keying) of a composition trough a blackmagic device?
I have this funtionality in many softwares (Caspar CG, Boinx etc.) so it appears to be something not impossible.
At the moment if i send a video signal from VUO to a Ultrastudio with alpha channel I’m not receiving the 2 signals (fill AND key) out of the device but twice the same.
Of course with Pro versin of Vuo

Any idea?
Thank you very much

Which Ultrastudio are you using?

As far as I’m aware, BM devices doesn’t support alpha in on one channel, but I’ve mostly used the Atem line, so this might not be applicable to the Ultrastudio line. If it works like the Atem’s, you will need a separate input to use as a keyer signal for the matte. This function isn’t available out of the box with Vuo, but it’s doable with a custom shader/node that you can find here: https://community.vuo.org/t/-/7129.

I’m not sure how Vuo handles framesync between outputs, but I haven’t had issues when using this approach before (your mileage may vary though).