Alpha channel bug in 15.2

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tylerhawes

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  • Joined: Mon Sep 07, 2015 4:11 am
  • Location: Vancouver, BC

Alpha channel bug in 15.2

PostWed Nov 21, 2018 10:34 pm

Spent a couple hours pulling my hair out until I found a solution to this, so thought I'd share.

I noticed after upgrading to Resolve 15.2 that any clips with alpha channels were no longer displaying correctly. Transparent areas are not completely transparent and the image becomes darker (like a steeper gamma). I tried about a dozen different formats for interchange, and Resolve had the same problem across the board. Just park an alpha clip above another clip and step a frame at a time. You'll see that when you step over the alpha clip, the composite image becomes darker like the transparent area has a low opacity black to it. Also the colors of your graphic will be off. This didn't happen in 15.1.

Anyway, the fix is simple (I wish I'd found it sooner). Just do *anything* to a color node for the graphic clip, and it'll snap back to proper display. I personally just added a point to the luma curve (shift+click near the curve and it'll make a point snapped to the curve so it doesn't effect the image). As soon as it forces this to be processed through the color page, the gamma bug is rerouted.

I assume 15.3 will fix this behavior, but this will get you by for now. Double-check ALL graphics with alphas, I found they were wrong without exception.
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Christopher Kou

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Re: Alpha channel bug in 15.2

PostFri Dec 14, 2018 2:42 am

I am also having this bug, and the workaround is not working for me. It actually renders out correctly . . . for the most part. There seems to always be a random frame that blinks in with the bad alpha matte bug. Please fix this ASAP, or I may be forced to finish the shot in After Effects. Blech.
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Sam Steti

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  • Location: France

Re: Alpha channel bug in 15.2

PostFri Dec 14, 2018 9:48 am

Hi there,

It's not impossible I saw the same issue here on graphics with alpha channels... These Pro Res 4444 used to work fine for years, issues showed up a few days ago with 15.2 indeed.

My workaround was to switch from "project settings" to "nearest" in the graphic parameters (I think it's in motion estimation mode, down the parameters panel, I'm not in front of it).
My project settings are set to optical flow normally...
*MacMini M1 16 Go - Ext nvme SSDs on TB3 - 14 To HD in 2 x 4 disks USB3 towers
*Legacy MacPro 8core Xeons, 32 Go ram, 2 x gtx 980 ti, 3SSDs including RAID
*Resolve Studio everywhere, Fusion Studio too
*https://www.buymeacoffee.com/videorhin
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Christopher Kou

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Re: Alpha channel bug in 15.2

PostFri Dec 14, 2018 5:42 pm

Yeah, changing Retime Process to Nearest didn't work either (also tried Frame Blend). It still flickers back and forth between good-alpha, bad-alpha. Screenshots attached.
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goodalpha.jpg
good alpha
goodalpha.jpg (777.78 KiB) Viewed 1884 times
badalpha.jpg
bad alpha
badalpha.jpg (782.19 KiB) Viewed 1884 times
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Christopher Kou

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Re: Alpha channel bug in 15.2

PostThu Dec 20, 2018 3:42 am

We've had to switch to After Effects for compositing because of this. Hopefully it will be fixed shortly so that I can return to a Fusion workflow.

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