I have a composure post process material used in a virtual production LED wall scenario. It masks out the LED wall but passes the foreground and set extension. To do this I have a cg scene capture layer as the main source connected to the Emissive Color pin. By enabling Alpha in my PPM the Opacity pin is enabled and on this I input the mask information. The documentation says this will output the key and fill on the blackmagic decklink card if these 3 things are set (which they are for me and it still doesn’t work):
- PPM has Output Alpha checked
- BMD Desktop video app has set the card to use 2 connectors for SDI 1 (or 2)
- The Media Output Blackmagic configuration selects the Key&Fill option
On my Decklink Duo 2 this all can be configured but the Key is black. Unreal appears to be driving the key connector because the black image is at the correct fps (and not the card default).
On my Decklink 4k pro card there is no Desktop video config to use 2 connectors. It appears to only support an “auto” setting but the result is the same and one output shows the fill and one other shows black at the correct fps.
In both cases I can run vMix and get a key and fill output so I think the card is capable but it seems the Epic Media Output Blackmagic does not work.
My project is on 5.4.4 but this issue has been there since 5.2 at least. Have I missed a step or is this a long standing bug?