Resolve: converting Luma Levels

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Sanjin Švajger

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Resolve: converting Luma Levels

PostSat Dec 14, 2019 11:56 am

Hi,

I have a project that was graded in Resolve in Data levels, used for DCP, originally exported in data levels. Now needs to be exported for broadcast, video levels. Need help, advice on exporting!

Workflow:

- Shot in Panasonic Log, Data levels
- Edited in Avid using proxies
- Exported to Resolve using DNxHR HQX
- Manually set video levels to Data levels on each clip in Resolve
- Monitored with video levels set in Video monitoring to video levels
- Now exporting to quicktime encoding to DNxHD 185 10bit

After setting levels to video in the delivery page, the exported video has washed out luma levels when previewed in quicktime player.

So I am in need of some advice. Apparently this workflow produces a video file that has video levels, in metadata of the clip, flagged as video levels but also squeezes the actual levels to video levels. I then do not understand why this doesn't play out correctly on desktop. It plays as if levels were flagged as data levels but actual levels in file are squeezed!

What to do? I know DNxHD is a video levels codec but I have no clue what is going on in Resolve now when exporting! How does Resolve handle DNxHD and what is actually going on with luma levels when exporting?

Thank you!

Regards,
Sanjin
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Andrew Kolakowski

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Re: Resolve: converting Luma Levels

PostSat Dec 14, 2019 6:01 pm

You can work in full levels if you control workflow and know/remember about it (and manually overwrite interpretation if needed), but...
for final deliveries don't use full levels (specially with codecs like ProRes, DNxHD/R etc). Leave it at default setting and let Resolve convert to video levels. It does it properly.

DNxHD/R can be both: video and full levels. Problem is that most apps don't set flag (or read) properly, so you should stay with default (video) levels for final deliveries. In 90% cases this will be also an requirement. ProRes should be always video levels (by its spec) although you can produce full levels files as well (but no flag which tells about it- needs manually interpretation).

If end result is wrong this is most likely place of a problem:
"Exported to Resolve using DNxHR HQX"
Do you know if this is not scaled to video levels by default during your export (if I remember well in AVID you have to specifically set levels)? When you import to Resolve you can check it quickly by looking at scopes and playing with levels setting in clip properties.
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Sanjin Švajger

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Re: Resolve: converting Luma Levels

PostSat Dec 14, 2019 6:43 pm

I am also certain that is where the problem lies. And if I remember correctly, I've come across this problem several times and it has to do with Avid - DNxHD - Panasonic data levels codec.

Export from Avid was I think (old project) kept at default, so this means video levels. But, resolve had problems interpreting this, so video levels had to be set manually to data because I think I had problems exporting.

I know, it's always best to export with video levels. It's just this combo/workflow that's giving me gray hair all the time.
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Andrew Kolakowski

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Re: Resolve: converting Luma Levels

PostSat Dec 14, 2019 8:53 pm

Sanjin Švajger wrote:
Export from Avid was I think (old project) kept at default, so this means video levels. But, resolve had problems interpreting this, so video levels had to be set manually to data because I think I had problems exporting.


Which means by overwriting it to full levels in Resolve you've created a shift (if you don't correct it with grading).
Reset it to video levels and all should be fine.
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Sanjin Švajger

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Re: Resolve: converting Luma Levels

PostSat Dec 14, 2019 11:44 pm

Andrew Kolakowski wrote:Which means by overwriting it to full levels in Resolve you've created a shift (if you don't correct it with grading).
Reset it to video levels and all should be fine.


I did that because the film didn't want to export properly, as far as I remember, it's an old project.

Either way, if I do that, I need to manually correct the grade, as converting the clips to video levels, stretches out the grade and clips the levels. Do you have any idea which function in resolve is linear and not logarithmic in order to manually clamp the levels?

I hope that will help because I really do think there was a reason for manually setting the levels to data...
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Andrew Kolakowski

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Re: Resolve: converting Luma Levels

PostSun Dec 15, 2019 10:49 am

If you corrected levels during grading then your export with default settings should look fine.
Which player shows it wrong, QTX?
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Sanjin Švajger

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Re: Resolve: converting Luma Levels

PostSun Dec 15, 2019 1:29 pm

QT and VLC.

Any idea on how to linearly squeeze the levels?

Tnx
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Andrew Kolakowski

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Re: Resolve: converting Luma Levels

PostMon Dec 16, 2019 10:14 am

If your scopes show correct levels after export levels will be correctly squeezed. Don't try to make them 64-940 in scopes- this is very wrong.
Use Switch player. I think your file is fine, but preview is wrong.
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Sanjin Švajger

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Re: Resolve: converting Luma Levels

PostMon Dec 16, 2019 2:34 pm

No no. The grade needs to be adjusted. When you change clip interpolation from data to video levels, luma levels get extended and clip. So you need to bring them back in range.
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Andrew Kolakowski

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Re: Resolve: converting Luma Levels

PostMon Dec 16, 2019 2:38 pm

No need to change it if you corrected it in grade.
As I said- if your current project is graded and correct then exporting at default settings to should give you correct end file. There is no need for any action (you just gave yourself bit more work in the 1st place).
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Sanjin Švajger

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Re: Resolve: converting Luma Levels

PostMon Dec 16, 2019 4:24 pm

Hm, I'm not sure I follow. My current export, as I said, produces data levels. If I manually select video levels, it isn't correct. This is for broadcast, and I don't want to deal with their technicians as it's public TV and don't event start me on how things work there.

Anyway, again, I need to change the grade. I cant just export with video levels and I can't just change clip levels to video levels and then export b/c this clips the low's and the highs. I am not sure you understand the predicament or I am reading you wrong. Tnx.
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Andrew Kolakowski

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Re: Resolve: converting Luma Levels

PostMon Dec 16, 2019 4:44 pm

If you see correct levels in Resolve/scopes then exporting with Auto (or forced Video levels) should be fine. You don't want to use Data levels for sure. You should not need to change anything either.
Your problem sounds strange. Are you on Resolve 16? Was this project created in some much older version?

In the same time be careful when validating your final file.
Are you on PC or Mac? QT 7 on PC quite often shows wrong blacks. It's not good reference player. Don't rely on it.

What happens if you import your final DNxHD file back to Resolve. Do you see correct levels in scopes (black need to be around 0 not 64)?

Upload 1 second sample of your final file.
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Sanjin Švajger

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Re: Resolve: converting Luma Levels

PostMon Dec 16, 2019 9:59 pm

As I said : ) manually setting the clip levels to video levels, streches out the luma levels on all the clips. Yes, visually and on scopes. So it needs to be manually adjusted.
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Andrew Kolakowski

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Re: Resolve: converting Luma Levels

PostMon Dec 16, 2019 10:04 pm

Don't touch it on source side.
I'm talking about output.


If you wrongly assumed Full levels in the past on source stage, but corrected it in grading then exporting with default setting should give you correct look (you just gave yourself bit more work). If you now change levels on source stage then your whole project will need correction. No need to do it if you already have correct grade.

Just export with default setting and it should be correct (what drives output is only current state in color page- full/video assumption on source is irrelevant).
If you still have problem then it's something strange.
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Sanjin Švajger

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Re: Resolve: converting Luma Levels

PostTue Dec 17, 2019 10:13 am

Yes. That is what I'm saying mate, don't want to be rude, but for the past 10 posts.

Just exporting with default levels produces a correct looking image BUT with data levels that gets rejected at QC on TV. So I need to produce a correct image with video levels. And I cant do that just by selecting video levels at export. I am telling you, it's a weird problem with avid and panny's data levels codec with dnxhd.

Anyway, tnx for the help. I'll figure it out. Actually hadn't had the time to sit behind the computer for 3 days now.

What I actually need is advice on how to manually clamp levels with a linear scaling function.
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Andrew Kolakowski

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Re: Resolve: converting Luma Levels

PostTue Dec 17, 2019 11:19 am

I just tried (latest v16 on Mac) and looks like DNxHD MXF export is broken. Actual data is always full range.
What worse file headers say it's Limited range (with Auto or Video setting). This means Resolve is not properly preparing data before it hits DNxHD encoder.
Export other codec (ProRes, 10bit YUV, Cineform) and use eg. ffmpeg etc. to encode to DNxHD.
Also- exporting as DNxHD in MOV works fine. It's only MXF which is broken.
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Howard Roll

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Re: Resolve: converting Luma Levels

PostTue Dec 17, 2019 5:11 pm

Sanjin Švajger wrote:What I actually need is advice on how to manually clamp levels with a linear scaling function.


You can create a timeline node, right click it and convert the gamma to linear. Using the gain wheel should give you most of what youre looking for.

Good Luck

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