Preparing UHD HDR 4K sources for DCP in 2026?

[theirongiant]

Hello,

I'm new to DCP-o-Matic and was attempting to create some sample reels for projection on a late model Christie 4K (exact model unknown) with an onboard Dolby IMS3000. Audio is routed to a Dolby CP950. Source material is a 4K UHD HDR Blu-ray title (I have a LibreDrive). An existing theatre has been upgraded / retrofitted with a new sound system. They have a standard Blu-ray player in the booth, but I wanted to try my hand at authoring some DCPs.

I found a number of (old-ish) threads on this forum about problems and workarounds for preparing HDR / ST2084 footage for playback on typical DCI projectors that use the P3-DCI colorspace:

- Conversion from Rec2020 to P3
- DCP Conversion of UHD Blu-Ray files resulting in Colour being off
- 4K UHD Blu-ray to DCP for playback on 2K commercial projector?
- Creating a DCP from a BluRay
- P3 color conversion to XYZ

All of the above posts and replies are at least 18 months old.

Assuming DCP-o-Matic is the packager...

- What's the current state of UHD HDR conversion to DCI XYZ 12-bit?
- Does the app support conversion and tone-mapping natively now?
- Is it still necessary to convert the source footage to a different color space (i.e. P3 or 709)?
- Is FFmpeg the best or only method for creating the intermediate footage prior to DCP authoring?
- Do similar workflows for footage conversion exist in DaVinci Resolve?
- Using Resolve, what's the best way to check the results on an M1 MacBook Pro (or newer) with its built-in HDR display?

Thanks!

P.S.: I'm an IT systems engineer with 15-years' experience and a background in the entertainment industry. I'm currently exploring a career transition to commercial AV. So far, I'm impressed by the capabilities in DCP-o-Matic: the controls seem intuitive, and it's taken all of the source footage I've thrown at it so far. The "Hints" are very useful, and the audio mapping options are convenient. I was able to configure a small cluster of spare Macs (2013 Mac Pro 12-core, 2018 Core i7 Mac mini 6-core, 2020 M1 Mac mini 8-core) running Encoder Server, and achieved ~13fps @ 4K. Ethernet became the bottleneck, actually: I couldn't keep the buffers full on the encoders until I gave my source Mac (M1 MacBook Pro) a 2.5GbE Ethernet adapter, and connected the other Macs to an unmanaged 10GbE D-Link switch. That boosted my render rate by ~50%!

[Carsten]

Carl recently hinted me to this:

https://github.com/zhangzhangco/dcpomatic-hdr


I don't know wether one would call this a 'fork', or a contribution.


Maybe you could give it a try and tell us what you think. My personal experiments with UHD HDR 4k discs was as discussed in these older threads.

[theirongiant]

Carl recently hinted me to this:

https://github.com/zhangzhangco/dcpomatic-hdr


I don't know wether one would call this a 'fork', or a contribution.


Maybe you could give it a try and tell us what you think. My personal experiments with UHD HDR 4k discs was as discussed in these older threads.

My account is too new to PM you directly, so I guess I have to ask this publicly. (Everyone else, please don't judge me for not knowing how to do this next part; git was brand new when I was in college, and I got a degree in audio engineering and digital media arts, not software development. I don't have ingrained best practices for managing git repositories and compiling code.)


That fork appears to have a build of dcpomatic for Linux. The only computer I have with a Linux OS installed is a Raspberry Pi 4B, and it obviously lacks a neural network. I generally don't build stuff from source regularly except for a few one-off projects that aren't available in homebrew. I may have to do this for ffmpeg just to get libzimg and other extras, because the homebrew build is missing a ton of features.

• Do I need the osx-environment files if I'm going to build this from the fork's source on a Mac?
• Carl's git source for the osx-environment is currently not responding: https://dcpomatic.com/building/osx
• Would the fork simply fail to build on a Mac?
• If I have the Command Line Tools installed from Xcode, do I need anything else?
• If I partition my M1 MacBook Pro to install Linux on another volume, is there any distro that can handle media workflows and/or display HDR content on the MBP display, or an external display via HDMI?

[barber]

Carl recently hinted me to this:

https://github.com/zhangzhangco/dcpomatic-hdr


I don't know wether one would call this a 'fork', or a contribution.


Maybe you could give it a try and tell us what you think. My personal experiments with UHD HDR 4k discs was as discussed in these older threads.

Hi,
This interesting fork aims at creating HDR DCI DCPs (I don't know whether there are definitive specs for this ? maybe https://documents.dcimovies.com/HDR-Add ... 7/#sec-7-1 ) from SDR sources.
Creating a classic SDR DCP from HDR source is another question. Currently, DCP-o-matic only supports SDR sources.
I haven't looked into this issue again since the posts you linked - where I suggested the use of a Color Space Transform node in Resolve. Give Kewl's ffmpeg commands a try as well.

Best,
Dan

[carl]

Carl's git source for the osx-environment is currently not responding: https://dcpomatic.com/building/osx

Sorry about that, I changed the git server around quite a lot recently to try and stop it being overrun by bots and I broke access to that repo. It should work now (though with https:: rather than git::)

[SethMutchler]

This is not helpful right now, but I met someone recently who claims to have solved the HDR > SDR conversion process. Creating SDR 4K DCPs from UHD HDR Discs has been my white whale for years, so I am excited about the possibility. But we haven't linked schedules yet for them to show me their process, so cannot share that yet, nor can I verify its validity. BUT, I have my fingers crossed I can provide info about this sometime in the next few weeks

[Kewl]

I intend to have a crack at it again, but with the help of Claude AI, resulting either in a FFmpeg CLI or something that could be applied internally in DOM.

[Carsten]

I don't think one should call this HDR->SDR, as DCP supports 12Bit linear Gamut, whereas in consumer HDR, SDR-Tonemapping is towards a limited range 16:235 4:2:2 Signal. That's why I think that common consumer HDR tonemapping methods are inferior as a preprocessing stage.

[Ross Meyer]

Hey folks,
Sorry to keep beating this dead horse but I've also done many tests of the 4K UHD to DCP process and so far I am also stumped. Sometimes the end result looks like an imaculate 4K DCP and other times I end up with a dark, murky mess. I realize this has everything to do with HDR. My question is, is there some way, before attempting the conversion process to assess the dynamic range of the original .mkv file to discover the red flags before the conversion process? Is there something in the meta data that will clue me in as to not waste my time? Or is it just something I should be able to spot with my own eyes looking at the file on my monitor? It seems that not all UHD discs are labeled as HDR and/or some that are not advertised as having HDR still end up looking like shit.

[Carsten]

I know at least as much as there is not a single representation of 4K/UHD, so, one needs to know what format is actually stored on the disc.