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Alpha channel difference prores vs dnxhr

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Nick Verlinden

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Alpha channel difference prores vs dnxhr

PostWed Jan 17, 2018 10:22 am

Using Fusion 9.0.2 build 15, I'm experiencing a problem when saving files with an alpha channel.

I have created a wipe using a 3d object, but get different results when using them in DaVinci Resolve Studio 14.2 (and 14.1).
When saving a Quicktime file with ProRes 4444 XQ (or any other ProRes), the alpha channel displays correctly in DaVinci Resolve, it is fully transparent and solid where it should be. But when I render a quicktime DNxHR or MXF DNxHR, the transparent parts seems to darken the video clip on the layer below it a tiny bit, and also where it should be solid it is a tiny bit transparent.

This behaviour is present in the Windows and macOS version. Since I'm using the free version, there is no way for me to test this if the same behaviour is present on Windows when rendering to ProRes.

I'm currently rendering my compositions on my macbook (this is the only available mac for me), but the estimated rendering time for all my compositions are more than a week. I would like to use my windows machine since it has a more powerful GPU present.

I may go another route, and render to PNG or something, and convert it to prores on my macbook. That way, I can embed audio so it is instantly usable in DaVinci.

EDIT: I have discovered that when you load the rendered DNxHD again in fusion, it displays correctly. That leads me to believe it's a Resolve bug, and have posted a new thread on that forum.

Alpha Bug (ProRes).jpg
ProRes
Alpha Bug (ProRes).jpg (254.21 KiB) Viewed 491 times

Alpha Bug (ProRes Split).jpg
ProRes Split Layer
Alpha Bug (ProRes Split).jpg (336.31 KiB) Viewed 491 times

Alpha Bug (DNxHR).jpg
DNxHR
Alpha Bug (DNxHR).jpg (265.98 KiB) Viewed 491 times
Last edited by Nick Verlinden on Wed Jan 17, 2018 11:43 am, edited 2 times in total.
Windows 10 x64
Core i7 950, 16GB RAM
GTX 1050 Ti 4GB
Blackmagic DeckLink Mini Monitor 4K
Blackmagic URSA Mini Pro
Blackmagic Pocket Cinema Camera
Blackmagic DaVinci Resolve Studio 14
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Nick Verlinden

  • Posts: 135
  • Joined: Wed Aug 12, 2015 11:08 am

Re: Alpha channel difference prores vs dnxhr

PostWed Jan 17, 2018 10:22 am

Alpha Bug (DNxHR Split).jpg
DNxHR Split Layer
Alpha Bug (DNxHR Split).jpg (334.98 KiB) Viewed 458 times
Windows 10 x64
Core i7 950, 16GB RAM
GTX 1050 Ti 4GB
Blackmagic DeckLink Mini Monitor 4K
Blackmagic URSA Mini Pro
Blackmagic Pocket Cinema Camera
Blackmagic DaVinci Resolve Studio 14
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Ignacio de La Cierva

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Re: Alpha channel difference prores vs dnxhr

PostWed Jan 17, 2018 12:10 pm

Checked video levels at export/import?

It might be Davinci reading bad video levels from the DNx. Then, your expected black alpha is not so black, and the same with the white.
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Nick Verlinden

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Re: Alpha channel difference prores vs dnxhr

PostWed Jan 17, 2018 12:24 pm

Ignacio de La Cierva wrote:Checked video levels at export/import?

It might be Davinci reading bad video levels from the DNx. Then, your expected black alpha is not so black, and the same with the white.


Hi Ignacio,

Do you mean these?
They where set to these values (of the screenshot) for both ProRes and DNxHD.
Screen Shot 2018-01-17 at 13.23.44.png
Screen Shot 2018-01-17 at 13.23.44.png (30.72 KiB) Viewed 434 times
Windows 10 x64
Core i7 950, 16GB RAM
GTX 1050 Ti 4GB
Blackmagic DeckLink Mini Monitor 4K
Blackmagic URSA Mini Pro
Blackmagic Pocket Cinema Camera
Blackmagic DaVinci Resolve Studio 14
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Sander de Regt

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Re: Alpha channel difference prores vs dnxhr

PostWed Jan 17, 2018 12:51 pm

Maybe they're set the same way, that's no guarantee that Resolve will import them in the same way.
How do the files compare in Fusion itself?
Sander de Regt

ShadowMaker SdR
The Netherlands
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Nick Verlinden

  • Posts: 135
  • Joined: Wed Aug 12, 2015 11:08 am

Re: Alpha channel difference prores vs dnxhr

PostWed Jan 17, 2018 12:54 pm

Sander de Regt wrote:Maybe they're set the same way, that's no guarantee that Resolve will import them in the same way.
How do the files compare in Fusion itself?


Hi Sander,

Indeed, I tested that after my post, and realised they both look good in Fusion. That's why I am starting to think this is a Resolve issue, and also poste the question there.
Windows 10 x64
Core i7 950, 16GB RAM
GTX 1050 Ti 4GB
Blackmagic DeckLink Mini Monitor 4K
Blackmagic URSA Mini Pro
Blackmagic Pocket Cinema Camera
Blackmagic DaVinci Resolve Studio 14

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