Blackmagic Forum

I've upgraded to Resolve 15, but I'm now having what I believe is a bug upon exporting keyed clips with an alpha background. In the edit, color, and even delivery timelines, the background is black. When I click to export it out of resolve on the delivery tab, but background turns green(I used a green screen). I click stop, the background remains green. I go to the edit tab, the background goes back to black. I click the delivery tab, the background remains black. I click export, the background turns green again.

I'm exporting the clips as prores 4444. Source footage is cinemaDNG.

Is this a bug, or am I missing something?

Thanks,
Feral

Did you wire the node for alpha? Are you exporting as individual clips and did you set the alpha export?

If not, the system may just be warning you that you don't get alpha.

The node used for the keyer is wired to the alpha output. Export alpha is checked on the delivery page. I am exporting individual clips.

Everything looks good until I click "Start Render". Then my background reappears.

Update!

Thanks to Uli Plank's question, I tried exporting as a single clip as opposed to individual clips. This solved the issue. My timeline now exports correctly with the alpha channel. I'd prefer individual clips, but I will make this work. Is Resolve supposed to work this way, or is this a bug?

Thanks,
Feral

Hmm, that sounds weird. Export alpha is not even offered if deliver is set to single clip.

That's accurate. When I selected export as single clip the export alpha option disappeared, but it seems to be exporting the alpha channel. I'll know in 1.5 hours when the export is complete. If it doesn't work out I'll just have to re-key in another NLE. I will update this thread when the export is complete. I'm still interested in knowing if this is a bug or not.

I can export alpha without any problems in ProRes 4444, DNxHR 444, DNxHR HQX or CineformRGB 16 bit.
Always in individual clips mode only.

But I can confirm there's a cosmetic bug: the key disappears in the viewer while exporting.

Don't worry, the alpha will be there!

When I export individual clips the alpha channel is not there on the final exported videos. It was not just cosmetic, unfortunately. Exporting as a single clip seems to be working. I will report back. Thank you.

Update:

Exporting my timeline as a single clip I was not able to export my clip with the alpha channel.

If you are working under Windows, we must state an inconsistency here.
Actually, I wouldn't mind to have the option of exporting alpha in single clip mode too. But our observations seem to differ massively. I hope other will chime in on the subject.

BTW, maybe you could change the headline to "Alpha Error on Export?"

I was mistaken. When exported as a single clip the background rendered out as black, but not transparent. No alpha channel. Currently I have no way of exporting clips with an alpha channel out of Resolve. Frustrating. My client has a deadline, so I will be switching to another NLE for this project.

I will update the thread title.

Did you:

– Generate any kind of key in a node?
– Add an alpha output in the Color tab?
– Connect the alpha output of your key or last node to that alpha output?
– Go for individual clips in Deliver?
– Define alpha and use one of the codecs mentioned?

Uli Plank wrote:Did you:

– Generate any kind of key in a node?
– Add an alpha output in the Color tab?
– Connect the alpha output of your key or last node to that alpha output?
– Go for individual clips in Deliver?
– Define alpha and use one of the codecs mentioned?

Yes. I generated a key in a node. Added an alpha out in the color tab. Yes the alpha output is connected to the key node. Yes I used individual clips as my export option and had the export alpha box selected. I exported proress 4444.

Everything looks and is correct until I click the render button. Even when I add the render job to the queue, it looks fine. Once I click the render button, the background reappears as if there is no key at all.

That is a cosmetic bug, as I already wrote. The alpha channel should be in the rendered file nevertheless.

Uli Plank wrote:That is a cosmetic bug, as I already wrote. The alpha channel should be in the rendered file nevertheless.

Perhaps I am misunderstanding what you mean by "cosmetic bug". What do you mean by cosmetic bug?

When I import the exported video files from Resolve 15 to another NLE, the green screen background is there- and it's green.

Below is a link of what I'm seeing:
you tube .com / watch?v=ffyzlAUkCHE&feature=youtu.be

By 'cosmetic' bug I mean I see what you are seeing, but the alpha is there if I import the rendered file into another NLE or Resolve itself. So, I can't really offer a solution.
But one thought: what resolution are you exporting?

I think I've worked this out. The timeline resolution and the export resolution need to be the same. Otherwise alpha doesn't work