Cannot export a video with a transparent background

Hi, I've searched for days for a video or post to answer this and found nothing. I have removed the green from a green screen effect video using the delta keyer in fusion. While in the fusion page I get the checkerboard background which seems to suggest I have transparency but in the color/edit/deliver pages I have a black background. I've added an alpha output to the color page nodes window and connected the blue square to the blue circle. I've also set the deliver page to quicktime, DNxHR DNxHR 444 12bit and checked enable alpha. I've also tried CinePro 16bit. I'm still getting a black screen. I've put the exported video onto a Davinci Resolve time line to test and imported into Blender so I'm certain there's no transparency.

In another post it was suggested that there should be a background layer with opacity set to zero. Tried this, no luck.

What am I missing?

I find it peculiar that the Delta Keyer should be so simple to use (the easiest chroma key system I've seen) but exporting transparency should be such a mystery.

I want to drop the video into a Blender scene so it needs to show only the subject.

Looking forward to the answer

Dave

Can you use Save node and export from Fusion?

I'll give it a shot when I get a chance.

I had the same problem like you, but was using the 3D keyer in the edit page timeline.

Do the following:

Export format must be Quicktime MOV
Codec: GoPro Cineform RGB 16bit

[X] Export Alpha
Alpha Mode: Premultiplied

Quality: High

Data Levels: Auto

Alternative option:

Export format must be Quicktime MOV
Codec: Grass Valley HQX

[X] Export Alpha
Alpha Mode: Premultiplied

Quality: High

Data Levels: Auto
[X] Retain sub-black and super-white


To get Resolve output your alpha channel in the color page:

Right click and select "Add Alpha Output"
Connect the blue alpha out from your node to the blue Alpha Output

It might be that you have to send your alpha out from the Fusion page, too - but that I don't know how to do, yet.

You don't appear to need to add an alpha channel on the Color page, nor do you need to add an alpha output on the Fusion page. I place a green screen clip on the timeline, entered Fusion, added a delta keyed, keyed the green then went to the Delivery page and exported as DNxHR 444 with the 'include alpha' checked. Exported and then brought it back into Resolve and dropped it over a background media - the alpha channel was present.

Did this on my MacBook (see signature).

Add - Tried with Grass Valley and Cineform as you suggested and got good results as well.

Cheers

Hi, thanks for all the suggestions. They were variations of what I'd already tried but I tried them again, still no alpha channel.

As far as I can tell I have done everything correctly. I wonder if it's a codec issue or a windows issue.

I've attached screenshots.

Cheers
Dave

Fusion Page.png (402.77 KiB) Viewed 14593 times

Fusion Page.png (402.77 KiB) Viewed 14593 times

Fusion Page.png (402.77 KiB) Viewed 14593 times

Steve, I did not suggest DNxHR because it seems to be very depended on the application if the alpha channel is working.

See here
viewtopic.php?f=32&t=76702

That's interesting - particularly that Resolve has no problem with it but Adobe does. I suppose the point of my post was not about the codec but about the workflow. Cineform and Grass Valley also worked for me. I'm not presently sharing these files with other apps - just using them within Resolve but glad to know that we have options. If I get a chance, I'll try the same test on my PC to see if there is any difference (again, just within Resolve). Thanks.

Thanks for all your help. I've tried all the suggestions and still only get a black screen on export.

I'm wondering if this is a feature only available in Studio?

I've solved it, and of course it was simple!

I needed to change from premultiplied to straight. That was it.

One thing to add. This was all so that I could import a transparent video into a Blender 3D environment however, even though reimporting the video into Davinci Resolve showed a transparent background, it still had a black background in Blender. I had to export as a Tiff then import an image sequence into Blender.

Hey presto, transparent background.

I hope this helps someone else down the line. I still think it's an area for Black Magic to work on.

Cheers

@Karmalution, you saved me on this. I've been tearing my hair out over this as well, but when you said, 'Straight' instead of 'Premultiplied,' it led me to go check something. I had neglected to set that properly. Well, it was correct, then I crashed. When I came back, I never looked at it again since I knew I had set it.
It came back from the crash set improperly. Once I set it correctly, all was fine.

That's why is so helpful when people come back and mention how they solved something. It kicked me in the butt to go check and sure enough, my user error was what was causing the problem.

Thank you....