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RGB to 2K DCP for theater?

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Ole Slyngstad
RGB to 2K DCP for theater?
on Mar 12, 2014 at 6:12:57 pm
Last Edited By Ole Slyngstad on Mar 12, 2014 at 10:36:38 pm

I have a little dilemma concerning colorspace and conversion from a HD file to DCP (XYZ).

I am submitting a short film for a festival soon and they want me to deliver the film as a DCP. I’m familiar with the process of making a DCP so I’m going to do it myself.

The file I have is a ProRes 422 HQ 1920x1080 @ 23.976p. The intended aspect ratio is 1.85:1 so I'm going to crop/scale the file in Resolve and go for the 2K DCI Flat 1998x1080 profile.

The problem is the color space. I’ve done the grading on a calibrated rec 709 monitor with gamma 2.2 in AVIDs color correction. We didn’t have the time to do it in Resolve but I was nevertheless happy with the results in AVIDs CC. But for some reason the film was exported with RGB color levels in the Quicktime same as source settings (not rec709!).

Black levels 16 got mapped to 0 and white levels 235 got mapped to 255. The film still looks good though because the grade was done with a calibrated 709 monitor, so there weren’t any useful information under 16 or over 235 that got lost. I think the reason this happened was because at the time Youtube/Vimeo were the intended destination for this short film. It was an amateurish decision not keeping it in 709.

So now I got this ProRes HQ file in RGB (0-255) that needs to be converted to DCP.

Here’s what I got in mind:

I’m using Resolves JPEG 2000 export along with its XYZ conversion and then I’m going to import that into to a DCP creation tool. I haven’t decided which one yet but I think it will be openDCP, or easyDCP if I can get mye hands on it.

But my big question is:

I know that the XYZ conversion in dependent on what you choose in the settings under easyDCP/JPEG 2000 Color Management timeline color space. What color space should I choose here? Obviously I can’t go for either of the Rec709 settings or P3 for that matter.

But what about the sRGB setting? I've got my eyes on that one. But will it work? Is this sRGB the same RGB you find in the export same-as-source setting in AVID? If this is the case, shouldn’t this sRGB setting in Resolve work pretty well for my XYZ conversion?

And isn’t it right that even though the conversion from 709 to RGB happened in AVID, my RGB file should still possess the same calibrated grading it had in the rec709 colorspace? Wouldn’t it really be the same as using a rec709 to RGB LUT? Correct me if I’m wrong. I do not have access to a XYZ/P3 DCI calibrated monitor/projector, so I only got one shot at getting this right.

Does anyone have any comments or tips on wether selecting the sRGB option as timeline colorspace in Resolve would be the correct method to do the XYZ conversion? And what should I choose for export; normally scaled legal video or unscaled full range data?

Also can Resolve conform my file from 23.976 fps to 24 fps without any hassle? I will conform the audio by speeding up the 48000 Hz audio tracks by 0,1 % to 48048 Hz and then export at 48000 Hz using professional audio software.

Hope someone can share some knowledge on this topic.

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Terrence Meiczinger
Re: RGB to 2K DCP for theater?
on Mar 12, 2014 at 8:24:50 pm

The JPEG2000 images from Resolve will not be DCI compliant, so you will need to make sure they are re-encoded during the DCP creation.

You don't have to crop/scale your images. If you leave it 1920x1080 it will play within the 2k flat settings with 39 pixels of black on each side, which is often unnoticeable. Just an option, doing the crop/scale is fine too.

When you export the video, just export as an image sequence. When you create the DCP, you will tell the software to interpret the sequence as 24fps. This will reduce the overall duration, which you will compensate for by speeding up your audio as you mentioned.

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Ole Slyngstad
Re: RGB to 2K DCP for theater?
on Mar 18, 2014 at 3:37:07 pm
Last Edited By Ole Slyngstad on Mar 18, 2014 at 11:59:49 pm

Hi! Thanks for good info.

Yeah, it's a small let down that the JPEG 2000's from Resolve are only profile 2 and not DCI compliant. It would've been a lot easier if they could be used directly in openDCP without re-encoding.

I appreciate the work you're doing on openDCP. I really like the app as it works great. As an independent filmmaker it's invaluable to have this free open-source solution for creating DCPs for film festivals.

The biggest challenge is of course the task of properly making the material DCDM, as I want it to be DCDM before I hit any DCP creation tool (like openDCP) because that way I will have more accurate control over the final results. I believe you wrote in another thread that this is the proper workflow.

What software would you consider the best in terms image quality (regardless of price) when converting material into DCDM. I'm not into hardware DCP creation tools and JPEG 2000 encoders (like Clipster or Barco). Someone mentioned that Scratch does a good job with XYZ and gamma conversions.

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