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?
Still no luck but wanted to add that I tried changing the Post Process Material from Opaque to Transparent. This allows me to, just to confirm, connect the Alpha pin of the last Over node to the Emissive pin to confirm that the alpha pin has the correct alpha signal. But when its connected to the Opacity output pin it does not affect the key output.
Also I was able to test this also with a Decklink 8k Pro and it behaves identically to the Duo 2.
Hi @cevanno!
There was a Media IO regression that went unnoticed that was recently fixed in 5.5 (unfortunately after Preview 1) which could be related with your issue. If you’re able to build from source, you could give it a try on UE5/Main on github, otherwise you would have to wait until 5.5 releases to try it out.
Note: I believe there’s still an issue where you have to disable “Just In Time Rendering” in the advanced category for your use case.
This is great news. On the job in question I had a foreground element that was a fire with smoke and the alpha key quality was not very good when attempting to use the matte comp layer to be the alpha. I hope that integrated key/fill will let me remove the matte layer (saving performance) and produce a higher quality key. We will see when 5.5 is released (or I get a chance to build from source).