Ultimatte + Unreal Engine results in a desynchronized composition masking

Development Cinematics & Media Virtual Production
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Hi! _//

We are facing a strange behaviour with our composing shot,
and hope that any of you can bring some light trough this issue.

Our setup is composed with a BM Ultimatte, a BM Studio Camera, 2 HyperDecks, UE 5.0.3

1 - Blackmagic Ultimatte performs the matte stuff, comming trough only one BM Studio Camera;
2 - Then, the 2 HyperDecks receives a media source and the matte mask;
3 - Get a result texture based upon a clip between the media source and the matte, using a post processing shader in the composing hierarchy, the Opacity output channel of the material.

image

But the issue came with that.
When the UE editor frame rate runs low or above of the recording specs, occurs a desynchronization of the textures, and then this occurs:
image

What are the appropriate steps to identify and solve this problem?

1 Like
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Is UE genlocked to the video sources? I wonder if lack of genlock could be the source of the problem.

3

Hello~ I also want to use Ultimatte12HD for external keying, but I don’t know how to transfer the keyed image to UE~~ How did you do it? Is there a demand for the capture card~ Then do you need to set anything in the UE?

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Did you ever figure this out?
I would have started with genlock, then checked the media sources to ‘synchronize with engine’… Plus used Timed Data Monitor to try to help assess where the timing is off.

I’m not clear on the Hyperdecks, though - were you recording the outputs from the Ultimatte before going into UE?