Colour space

Anything and everything to do with DCP-o-matic.
LLdcp
Posts: 4
Joined: Sat Mar 13, 2021 8:40 pm

Colour space

Post by LLdcp »

Dear DCP-o-matic Team,

I noticed that importing a Pro Res 4444 tagged as P3 D65, DCP-o-matic seems to read it as colorspace REC709 (s. attachent). Since I am setting a P3 colour conversion, do you see a problem? Or should I go for the REC709 setting instead?
Thank you!
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P3 read as REC709?
P3 read as REC709?
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Carsten
Posts: 1830
Joined: Tue Apr 15, 2014 9:11 pm
Location: Germany

Re: Colour space

Post by Carsten »

ProRes native colorspace is rec.709. While it may be flagged internally in the file as P3 correctly, DCP-o-matic's underlying FFMPEG framework may not detect this properly - hence the content properties you see. You should also see colors being far off in the DCP (whites/greens) if you let it use the wrong colorspace. So, set it to P3 manually. It is not a good idea to use non-standard video formats/properties.
Last edited by Carsten on Wed Mar 17, 2021 1:54 pm, edited 1 time in total.
LLdcp
Posts: 4
Joined: Sat Mar 13, 2021 8:40 pm

Re: Colour space

Post by LLdcp »

Thank you, so Ill go for P3!

L
All4one
Posts: 4
Joined: Tue Jul 06, 2021 10:24 am

Re: Colour space

Post by All4one »

Hey Guys,

I have the same Problem.
I exported a File (DNxHR HQX, but tried some others) from Resolve. The Grading is made in a cinma grading studio with a P3 projekter so the image looks a little bit "washed out" on a Rec.709 screen. Timeline in Resolve is P3 D65, and "Taged Color Space" while exporting is P3 D65 as well.

Like LLdcP already described, when I now import the file in DCP-o-matic, it is labeled as "Colorspace" BT709, but got taged as D65 at "Colour primaries".

Now when I create a DCP with Color Transformation "P3" the Colores get really green.
When I create a DCP with Color Transformation "Rec709" the colores look like before, which is how it should be I would guess?

But when I click Rec709 for Colortransformation, all the "good" information from my P3 Colorspace is lost, isn't it?
Carsten
Posts: 1830
Joined: Tue Apr 15, 2014 9:11 pm
Location: Germany

Re: Colour space

Post by Carsten »

Weird. How can DCP colours be correct for an actual P3 master export if it is processed as rec.709 in DCP-o-matic?

With 'colors look like before' - do you mean in DCP-o-matic preview, or did you actually watch the resulting DCP in the cinema?

Can you upload a short snippet of your P3 master somewhere - ideally with some 'near neutral grey' in it (like e.g. a street surface or similar)?
All4one
Posts: 4
Joined: Tue Jul 06, 2021 10:24 am

Re: Colour space

Post by All4one »

Yes I mean on my Rec709 screen "it looks like before". I just realised that its probably normal that the image gets green in XYZ Color Space?
But I am just not sure if I am doing it right

I made a color space transformation in Resolve from p3 to xyz, rendered out a DNxHR, and made a DCP with "no color transformation" with DCP-o-matic. The DNxHR is really greenish, wich should be okay. After I created the dcp and open the mxf. is looks like rec.709 (vlc or dcp player). Why is that?

By the way, when I load the DNxHR with xyz color space again ins Resolve, its not so greenish anymore, probably because it is applying a color transformation?

On Friday I will be at a cinema, but I do not really have time for mistakes :(

Here are three files (DNxHR with p3, DnxHR with xyz, DnxHR with Rec.709, all rendered out from resolve):
https://we.tl/t-EwNjD67RR0
Carsten
Posts: 1830
Joined: Tue Apr 15, 2014 9:11 pm
Location: Germany

Re: Colour space

Post by Carsten »

Normally, you make a mistake by creating an xyz transformation in Resolve. If you create a master for DCP creation, and if you work in P3 in Resolve, you have to leave out the xyz transformation and create a P3 RGB master (P3 is RGB).


The xyz is done in DCP-o-matic, based on the assumption/setting that the source is either rec.709 or P3-RGB. Having xyz in anything else than a DCP or a DCDM (xyz encoded TIFF sequence) means it is a non-standard format and you have a hard time finding software or parameters to deal with it properly, both colorspace and gamma wise.

Which version of Resolve are you using?
Last edited by Carsten on Tue Jul 06, 2021 4:17 pm, edited 1 time in total.
Carsten
Posts: 1830
Joined: Tue Apr 15, 2014 9:11 pm
Location: Germany

Re: Colour space

Post by Carsten »

Looks as if DCP-o-matic is correct in indicating the P3 file as rec-709, MediaInfo (if you don't have it, get it!) indicates it as DNxHR HQX with 4:2:2 12bit YUV. Basically, this is just a plain YUV in 4:2:2 12 bit. Not the worst format, but probably not what you intended. Also, the color primaries are indicated as 'Display P3'. Display P3 is not DCI-P3.
Something is going wrong when exporting the file from Resolve. The XYZ version though is indicated as RGB 4:4:4 12Bit. It would be interesting to watch this in a cinema when being put through DCP-o-matic with color processing set to 'none'.

Yes, finding the right, ideally lossless intermediate master format towards DCP mastering can be complicated. I assume this is done in Resolve for windows?
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All4one
Posts: 4
Joined: Tue Jul 06, 2021 10:24 am

Re: Colour space

Post by All4one »

Yes I use Resolve on a Windows PC.

Do you think it really is an export setting problem with resolve? Carsten you already said that "ProRes native colorspace is rec.709." Probabbly DNxHR is not that different? So DNxHR alsways is Rec.709?

The Projektor and the guys from Arri told me that they used P3-D65 for the grading. So this is also what I have to export they said. Thats why I use P3-D65 and not P3 DCI. Should not be a problem?

So what is your Idea, what can I change? I can send you the "original" file so you can maybe find a working solution?
Carsten
Posts: 1830
Joined: Tue Apr 15, 2014 9:11 pm
Location: Germany

Re: Colour space

Post by Carsten »

What version of Resolve do you currently have your project in?

Currently, although I wrote 'you made a mistake' above, it looks as if from the three examples the XYZ version looks best from it's media file properties. The only uncertainty is the encoded gamma - if you put this through DCP-o-matic with color conversion disabled, it has to have an inverse 2.6 gamma encoding. Otherwise, the colors are correct, but the contrast rendering is bad. Also, XYZ files are usually meant to be full swing/data levels. The file you supplied is limited/video range. But you should be able to correct this in Resolves export dialog. In DCP-o-matic 2.15.x, there is also a setting to correct this. I created a DCP from the XYZ version though and at first sight, it looks okay to me. However, one would have to look at other parts, especially high key and low key scenes to check shadow and highlight rendering.

P3 definitely needs to use an RGB color model. In most cases, P3 masters are transferred using TIFF or DPX sequences - also in order to have a lossless master. While I do have an installation of Resolve on my Mac, and I went through the export settings dialog of Resolve more than once, I wouldn't say I'm an expert in Resolve.

What did the people at ARRI deliver back to you from their grading job? The full Resolve project, or some intermediate file?

Yeah, I know, finding the best format for master export is a pain in the ass on windows systems - essentially, because the windows version of Resolve is missing Prores exports...

According to this page: https://avid.secure.force.com/pkb/artic ... ifications

only DNxHR 444 is able to transport 4:4:4 RGB colorspace. All others use 4:2:2 and so necessarily use some form of color subsampling/color components, resulting e.g. in rec.709



- Carsten
Last edited by Carsten on Wed Jul 07, 2021 12:48 am, edited 5 times in total.
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