HDR mkv file to the best color space

[maxwellwCT]

I'm surprised this hasn't been brought up yet (well, only once before kind of). I am looking to convert a 4K HDR mkv file to the best possible DCP format so that the Christie projector at my work plays it. We (the projectionists) love DOM for our preshow material, among other things.

DCP-o-matic accepts my mkv file and I can even select the color space I want. I took a guess that P3 was the highest color space this projector would accept. Total guess.

The preview window shows me a pale, white washed image. Will it properly convert HDR to SDR?

[Carsten]

Common consumer HDR formats are based on static or dynamic metadata for global and/or local dimming of direct view screens, at higher luminance levels than are achievable in cinema. I haven't seen a proper way to convert them to 12bit x'y'z'. My test with an HDR UHD disc was unsuccessful, the standard Bluray looked much better.

[maxwellwCT]

Ah thank you. My 2021 MacBook Pro will likely be the only place I can watch hdr content

[Carsten]

It would be interesting to see what happens if you connect that MacBook to a D-Cinema projector.

[IntMarine]

Is it not possible that this is a linear to log conversion problem?

An OCIO Display Transform implementation is required perhaps?

[IoannisSyrogiannis]

Tone-mapping is not a transparent, one-solution-fits-all procedure.
Especially because the conversion profile is not consistent throughout the video files, but relies on extra metadata.

The funny thing is that checking with a player on your computer might be misleading, since many media players nowadays do the job automatically.
So, what you see on mpv or vlc is not what the input is on DCP-o-matic.

There are solutions proposed out there, making use of the zscale tone-mapping for ffmpeg, that might output a fairly good SDR file to make use on DCP-o-matic, but it will not be what an HDR player to SDR (or EDR, if you will) display would offer.

I am one between many who would love to have a straightforward solution to that matter, so I may use available material without asking for another master, but haven't yet found anything. I invested a few hours looking online for one, but to no avail.
If you do, anyone, please share.

[SethMutchler]

Reviving this thread. Any updates on how to take an HDR mkv file and create a DCP without losing accurate color representation?

My particular need is to go from a 4K UDH Blu-ray to a DCP, using MakeMKV and DCP-O-Matic as intermediate tools. More and more often our theater is booking titles on Blu-ray and we're converting to DCP for stable playback. We haven't had any films ONLY available on 4K yet, but many titles have recently re-mastered 4K discs, and the standard 1080 Blu-ray is an older release, so there are tangible non-strictly-resolution advantages.

FWIW, we have a 4K projector (Barco SP4K15-B), so would be creating a 4K DCP, but my understanding that this issue would equally stand for 2K.

I posed this thread to a colleague who is very knowledgeable on such things, and he said:

"I’m already starting to see HDR issues pop up in unexpected places. Now that phones have an “HDR” setting (not sure that it is really true HDR, but that is a separate conversation), these are starting to come in. I’ve done some conversions (in Resolve and Premiere - not in DoM) and the results were…fine. I could see differences in the side-by-sides that I didn’t love, but it wasn’t glaring enough that they audience ever thought that there was a problem. But this was a director’s intro shot on a phone…not a movie.

Overall, I’m honestly not sure that it is worth the trouble - the 4X render time on the 4K DCP, the higher data rate/scan time for the MKV with an end result of a higher resolution (that might not be perceived to the eye) that went through what is essentially a color space “down conversion” (instead of an "up conversion" from REC 709 to P3). All of this could make the final product the same or even worse.

That being said, I think that it is still worth pursuing. First, it will be fascinating to see the quality differences between a 4K HDR that went through all of this versus a 1080P. Also, do you have a 4k BR player that you can connect in? Would be interested to hear how that looks compared to something that went through this process.

But the biggest reason to keep on it is that it is likely that you will receive something in the future that is ONLY available as 4K HDR and you will need a workflow to deal with it. So, even if you test and find that the 1080p workflow is the same/better than the 4K, you will save yourself a lot of stress by getting it down now."

Thoughts? Willing to include Premiere, Resolve, After Effects, etc. in the workflow as needed, although staying within DOM would be ideal.

I'm currently in denial about not being able to convert these wonderful new re-releases when available and having to use 2010 crummy 1080 sources instead. There has to be a way!

Thanks in advance!

[Kewl]

This is my recipe: https://dcpomatic.com/forum/viewtopic.php?p=9307#p9307