Hyperdeck Mini alpha output

I've been struggling trying to load a simple transition effect to the Hyperdeck Mini that uses the both the fill and key outputs.

The Hyperdeck mini sees the file (a Quicktime format DNxHR SQ codec 720p 59.94) but both the A and B outputs only send the fill, neither send the alpha.

I've loaded the file into Adobe Premiere CC to ensure that the alpha channel exported onto the file correctly and it does indeed have the alpha channel... so why does the Hyperdeck not send it on the B output?

Any help is much appreciated!!

Hi !
Because you HAVE to use ProRes4444 for fill and key output.

It works very well.

Regards,
William

Ugh, I should have figured that would be the answer.

Is there a particular reason to not work with more formats?

Many thanks!