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Scott Clements
Problems with LUT being read in Resolve to Avid Workflow
on Jun 21, 2017 at 8:50:48 pm
Last Edited By Scott Clements on Jun 21, 2017 at 10:50:21 pm

Hi, Guys.

I'm trying to transcode Arri Mini rushes in Resolve with the built in Arri Log C to rec 709 LUT, and then bring them into Avid. However, these transcodes do not look the same as the original AMA-linked ProRes 4444 files (that have an embedded rec 709 LUT) The AMA-linked files look a bit more contrasty.

I have no idea why the transcodes look more milky. I'm also not sure why the embedded LUT in the AMA-linked ProRes files automatically shows up, whereas it does not automatically show up when the same files are brought into Resolve.

Does anyone have any ideas why the transcodes are milkier than the AMA-linked ProRes files? Could it be that the embedded rec 709 LUT is of a different type than the one I apply in Resolve? Is there no way to extract the embedded LUT from the ProRes 4444 files and apply it in Resolve? Thanks.

Film Editor, London UK
http://www.scottclementseditor.com


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Scott Clements
Re: Problems with LUT being read in Resolve to Avid Workflow
on Jun 21, 2017 at 10:53:45 pm

Someone told me about the Arri Color Tool and I think I figured out how to export the embedded LUT from the original ProRes 4444 and then brought it into Resolve. However, the transcodes are still lighter than the transcodes done to the same original ProRes 4444 footage in Avid. I can't figure out what's causing the difference. Not sure if I have my project settings wrong, but I'm mostly using the defaults.

Film Editor, London UK
http://www.scottclementseditor.com


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Marc Wielage
Re: Problems with LUT being read in Resolve to Avid Workflow
on Jun 21, 2017 at 11:17:00 pm

Is there a setting to switch Video and Full Data Levels?

I would export a short piece of SMPTE bars and look at them on a scope to determine what's changing (if anything) within Avid.


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Scott Clements
Re: Problems with LUT being read in Resolve to Avid Workflow
on Jun 21, 2017 at 11:20:35 pm

There is a switch for Video and Full Data in Resolve. I believe I tried switching it (I'll try again) but read an article saying that you almost never have to change it from auto. Regarding SMPTE bars - I'm super rusty on all that stuff - wouldn't really know what I was looking for.

Film Editor, London UK
http://www.scottclementseditor.com


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Marc Wielage
Re: Problems with LUT being read in Resolve to Avid Workflow
on Jun 22, 2017 at 1:05:38 am

I mean the switch in Avid. Resolve is generally reliable.


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Dennis Kutchera
Re: Problems with LUT being read in Resolve to Avid Workflow
on Jun 22, 2017 at 2:04:12 am

I highly recommend that you familiarize yourself with SMPTE colour bars and scopes. It is an absolute reference that will tell you precisely what is going on with levels. It is not something you want to be rusty on.

The Arri camera records Prores 4444 XQ, which is 12 bit RGB. The problem you are having is likely due to the RGB or as Avid now calls it, Full levels, being interpreted as REC 709 or in newer Avid speak - Legal Range. So, it is lifting black from 0 to 16 and dropping white from 255 to 235, which is correct for REC 709, but not for RGB. You end up with a lower contrast image than what is correct. This misreading of levels tends to be a Quicktime problem. Using an MXF container instead of Quicktime, I have never seen this misreading of levels occur. If you are linking and transcoding in Avid, go to the source settings for a clip and try changing the GFX-Video Level settings to where you see black and white on the indicated baselines.



If this works, then you can select all the clips in the bin, and do this modification to all of them, and then transcode. This only works when the files are linked, not if they are already transcoded or imported,

If you are importing the shots and not linking, then change the setting in the import options under color levels to whatever one solves the problem, likely "Scale from full range to legal range"



I hope this helps.

Dennis

Dennis Kutchera
Online Editor / Colourist
Halifax, Canada


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Scott Clements
Re: Problems with LUT being read in Resolve to Avid Workflow
on Jun 22, 2017 at 9:44:50 am

Thanks, Dennis.

Sorry, I can't get the quote feature working here, so improvising. Here's what you said: "The Arri camera records Prores 4444 XQ, which is 12 bit RGB. The problem you are having is likely due to the RGB or as Avid now calls it, Full levels, being interpreted as REC 709 or in newer Avid speak - Legal Range. So, it is lifting black from 0 to 16 and dropping white from 255 to 235, which is correct for REC 709, but not for RGB. You end up with a lower contrast image than what is correct."

Actually, the AMA-linked version, which appears to set the blacks at 16 and the whites at 235' makes a higher contrast and darker image than the resolve transcodes, which appear to have their blacks lower (at 0?) and whites higher (255?).

Here's the waveform of the AMA-linked footage in Avid:



Here's the waveform of the grade before it leaves Resolve:



Unfortunately, when I export the Resolve grade as an MXF and bring it into Avid, the waveform also has the black sitting around 16, so I'm not really sure what's going on.

You also said: "If you are linking and transcoding in Avid, go to the source settings for a clip and try changing the GFX-Video Level settings to where you see black and white on the indicated baselines."

I tried changing, based on your picture this and it did nothing to the appearance of the AMA-linked clips.

I have no idea how to make heads or tails out of this. I don't know what is considered correct.

Film Editor, London UK
http://www.scottclementseditor.com


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Scott Clements
Re: Problems with LUT being read in Resolve to Avid Workflow
on Jun 22, 2017 at 10:33:46 am

Someone in the Avid forums told me I should not have the "Levels scaling (video levels to full range)" color transformation on the AMA-linked clips. Avid does this by default.

When I removed that color transformation, the AMA-linked clips matched the look of the Resolve transcodes exactly.



This seems to me to mean that Resolve was handling the footage correctly, but Avid was forcing an uneccessary transformation onto the footage.

Film Editor, London UK
http://www.scottclementseditor.com


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Glenn Sakatch
Re: Problems with LUT being read in Resolve to Avid Workflow
on Jun 24, 2017 at 4:22:21 pm

If footage doesn't look right in Avid,

1-check your import settings (full vs legal) and
2- if you are linking, check to see what transformations Avid has applied in the source settings dialog page.
(more times than not, i have to go and delete all those transformations)

In Resolve, i always set either Video or Full instead of Auto...i want to know what it is going out as. Helps with step 1 above.

Glenn


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Scott Clements
Re: Problems with LUT being read in Resolve to Avid Workflow
on Jun 24, 2017 at 7:18:10 pm

Hi, Glenn.

None of these approaches in Avid match any output of resolve. I have tried everything. The only thing that matched the Resolve transcodes was this: removing the first color transformation that AMA made automatically : 1. Levels scaling (video levels to full range). I left the 2nd color transformation: 2. ARRI 709.AML (embedded). This made the transcodes from Resolve match the AMA clips. Even though I left the Resolve transcodes set to Auto, I did tests were I switched to Video, which did nothing and Full, which made the transcodes even darker than the AMA defaults.

People on Avid forums said that the first color transformation should not have been added because Arri ProRes is always at video levels.

This is all a total mess though. If it is true that the AMA default settings are wrong, then Arri made a bad Avid AMA plugin.

Film Editor, London UK
http://www.scottclementseditor.com


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Glenn Sakatch
Re: Problems with LUT being read in Resolve to Avid Workflow
on Jun 24, 2017 at 10:24:31 pm

Thats my point on auto...it will pick either video or full, based on the codec you select. (444 is supposed to be full i believe)

My point is rather than try to figure out what it chose, choose one for it and then you at least know how it was rendered out. If it is rendered out at auto, i have a 50/50 chance of guessing which tranform to choose in other programs.

As everyone is finding out on, going from one program to another is not always a perfect science.

I have become custom to adding a splash of bars and a greyscale ramp to the head of any file that has to go from Resolve to Avid. I find DNX444 is bang on. I find mxf files are so close that they might as well be bang on. Pretty much any other quicktime is a shot in the dark.

Last month i was going from Resolve to DS, and ended up outputting AVIs to get a perfect match.

As for Avids color interpretation setup, i'm always finding flaws with it, and just cleaning it out.

I am surprised you would need any transformation for the rendered clip out of Resolve (did you say it was 444?)

Perhaps try a couple different codecs, again with bars and ramp at the head, to see how they are affected in Avids world.

Is your Avid project RGB? That can affect what you are seeing as well.

Glenn


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Scott Clements
Re: Problems with LUT being read in Resolve to Avid Workflow
on Jun 24, 2017 at 10:39:38 pm

Hi, Glenn.

I understand.

My Avid project is not BGB, but YCbBr 709.

Here are more experiments I did that I posted in the Avid forums:

If I remove the "Levels scaling (video levels to full range)" color transformation from the AMA-linked ProRes 4444 clip and still keep the rec 709 Lut applied....

And then render out a flat transcode from Resolve, with no LUT applied and bring it into Avid...

I can only get the flat transcode to match the AMA clip, if I change it's source settings to add the rec 709 Lut and then the "Levels scaling (full range to video levels)"

But, if I just bring in the AMA and the flat resolve transcode and then just apply the rec 709 LUT, they look different

And this is the kicker....I can get the flat resolve transcode to match the AMA-linked defaults (of video to full, followed by rec 709) if I change its source settings to this: Levels scaling (video levels to full range), then I add the rec 709 LUT, then I add Levels scaling (full range to video levels). That's 3 separate transformations.

Weird. I don't really know what all this means. I am thinking of rendering out flat Resolve Transcodes as an emergency backup.

Film Editor, London UK
http://www.scottclementseditor.com


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Glenn Sakatch
Re: Problems with LUT being read in Resolve to Avid Workflow
on Jun 25, 2017 at 12:16:13 am

What are you transcoding these to in Resolve? You said the originals were prores444s, but I don't think you said what you were transcoding them to to bring back into Avid.

Glenn


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Scott Clements
Re: Problems with LUT being read in Resolve to Avid Workflow
on Jun 25, 2017 at 12:19:15 am

I am transcoding from ProRes 4444 to DNxHD 115 mxfs. I then put the mxfs in a numbered avid folder, rescan and put the database file in an Avid bin.

Film Editor, London UK
http://www.scottclementseditor.com


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Glenn Sakatch
Re: Problems with LUT being read in Resolve to Avid Workflow
on Jun 25, 2017 at 4:27:31 pm

It gets very confusing with all the transformations you are going through to totally follow along.

So you are taking a file that probably should be tagged as full levels into resolve, and you are outputting it as mxf as auto, which is typically going to get tagged as video, and it appears as though it is. You tried turning off auto, and video looked the same.

You might want to check in Resolve the clip attributes, and see how resolve is viewing the clip. Switch it from auto to video or full and which one changes the image. Perhaps Resolve is interpreting it as video instead of Full.

"I can only get the flat transcode to match the AMA clip, if I change it's source settings to add the rec 709 Lut and then the "Levels scaling (full range to video levels)"

I'm not sure how a flat transcode out of resolve would need a 709 lut added in Avid. Flat usually means it still looks ...flat.
Are you saying when you bring your flat transcode into Avid it already has a 709 look to it?

What are your camera raw settings set to in Resolve? Sounds like you have some metadata being added somewhere along the way that might be leading to the issue. Do you have a view lut or anything like that going on in the resolve color management?

Glenn


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Scott Clements
Re: Problems with LUT being read in Resolve to Avid Workflow
on Jun 28, 2017 at 3:55:59 pm

Sorry for the delay in responding. The project is now over and everything turned out fine.

"Are you saying when you bring your flat transcode into Avid it already has a 709 look to it?"

No, it's flat, but at least I can start at the same place as the AMA stripped of it's colour transformations to see what's going on.

"What are your camera raw settings set to in Resolve? Sounds like you have some metadata being added somewhere along the way that might be leading to the issue. Do you have a view lut or anything like that going on in the resolve color management?"

Sorry, I don't know Resolve inside out - not familiar with 'camera raw settings' - can't check now, as I no longer have the rushes. The ProRes files had an embedded LUT, but Resolve didn't see it. I could see it in the Arri Color tool, and Arri's Avid AMA plugin used it.

I feel very confident Arri's Avid AMA plugin is wrong. I looked at it on some shots where it was crushing the blacks way too much and I knew it was way off.

Anyways, the project is over, so the heat is off. I'll contact Arri about this and see if they know what's going on. Thanks for the help!

Film Editor, London UK
http://www.scottclementseditor.com


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