Blackmagic Forum

I need to render out the right half of a video either on black or alpha. So I added a power window, added an alpha output. Everything appears fine in the edit and color pages. I can place video under my track and it shows just as it should. The alpha power window is working (note, I remove the video below my video when I export. I just put it there to make sure alpha is working).

When I go to the deliver page I see the right half of the video, and the left half is gray, just as it should be.

But, no matter the codec or settings I choose, it always exports the entire video frame. Exporting is ignoring the alpha power window. I don't actually need alpha, black would be fine, but I can't get that to work either. I'm trying to render "individual clips."

You should see an 'export alpha' checkbox in the Video tab when rendering as individual clips

Thanks for the reply. Yes of course I see that. I've tried it on and off with various codecs.

You have to be sure that the codec you've chosen supports alpha channels. Prores 4444 will work, for example, but Prores 422 HQ won't. Apologies if this is obvious, but we should narrow down the possible causes in order to pinpoint your problem. Are you on a PC or Mac?

Thanks for the reply. I'm on Mac, latest version of Resolve. Yes I tried ProRes 4444, and I tried it with and without alpha. Like I said, I actually don't need alpha. On black would be fine.

I was able to do it if I export the clip on black if I exported it as a "single clip."

But I don't understand why alpha isn't working on Individual clips export.

LukeCypert wrote:But I don't understand why alpha isn't working on Individual clips export.

I bet it *is* actually working.

Try re-importing one of the single clips you exported.

While DaVinci is exporting, it just shows the RGB channels in the render view, even if there's an alpha channel in the file. Same goes for the viewer in the media browser. So, unless you're checking the files in another app (Finder quicklook seems to work for pr4x4) or fully re-importing them into DaVinci, you won't see the alpha channel.

Elsewise, I'd say make sure unmix is inactive on the color page (so white icon, not orange icon) and that the "clips" disclosure triangle dropdown menu at the top of the deliver page is set to "all clips."

Hope that helps.

-J

Jason Conrad wrote:

LukeCypert wrote:But I don't understand why alpha isn't working on Individual clips export.

I bet it *is* actually working.

Try re-importing one of the single clips you exported.

-J

Wow, ok, I feel dumb. I guess I had no idea how alpha works!

You're right, Resolve just shows the full video while exporting, but the final file does have the alpha channel working as it should.

Thank you!!