BluRay UHD HDR Conversion to DCP

[NocioSolo]

Hi guys,
I'm quite new in the industry and, above all, I'm self-taught.
I am the president, as well as the video/audio/general multimedia technician, of a cinema association that promotes its activities in a small Italian town (hence my bad English); I wanted to ask you if there is a way, which is not overly expensive and can be done autonomously, to convert UHD HDR blurays to SMPTE DCPs.
Do not worry, I'm not a pirate, but only a person who wants to have the highest possible quality when projecting movies under license.
In our cinema we are supplied with a Christie Solaria One projector, which should allow the reproduction of 35 trillion colors.
So far, to create an "HDR DCP", I have tried several solutions including:
- convert 4K HDR BDrip directly to DCP via wraptorDCP (in Adobe Media Encoder), but I do not have all the control I have with DOM, even if the result is closer to the original (with different colors and color space, and no audio managing).
- convert files in h265 rec2020 10bit not HDR and create the DCP in rec.2020 color space (as always), but the colors are still washed out.
- I tried to apply LUT to the SDR video to make them similar to the HDR one, but with bad results.
I noticed that easyDCP plans to create HDR DCP content, but no dates are specified and the prices are quite high.
I've been looking for a long time on the internet, and I've tried so many methods; whatever solution comes to mind is welcome, no matter how long or heavy it is.
Thanks in advance

[Carsten]

What you are after is a HDR->12Bit XYZ mapping. I haven't put much thought in it yet, but from what I know about target peak brightness ('nits'), different encoding curves and standards (Dolby Vision, HDR10/+, HLG), this is not easy to get through. As a matter of fact, there is a good deal of creative decision making involved, as digital cinema uses 12Bits, but has lower target peak brightness than typical HDR. So, if you convert a file straight from an UHD source into 12Bit, you may still find many scenes being too dark, or clipping, or..., and be forced to adjust them scene by scene, because cinema projectors (with the exception of the Barco ICMP) so far can not deal with consumer HDR.

Also, while your solaria is a DCI projector, it is one of those S2K machines with a rather low contrast capability, so, it is not really HDR capable.

It still is an interesting task to find workflows for this, I guess. I have no idea in how far FFMPEG currently supports common HDR formats.
I am sure it is not impossible for DCP-o-matic to use optimized HDR->DCI conversion parameters once this is sorted out.
Currently, I wouldn't even know if the tools you use for extracting the content will keep the HDR metadata in the converted file.


It is still too early for HDR in DCI cinema. There are some proprietary solutions (Dolby Cinema, Eclair Color), but no standards yet. On recent CinemaCon, YMAGIS came up with a metadata approach for HDR/SDR in SMPTE DCPs, but that is not a standard. It would take many years to make this (or another approach) a standard: https://www.dcinematoday.com/dc/pr?newsID=5063

I have been watching the formal development of Interop->SMPTE DCPs closely during the recent years. From that experience, I must assume that we won't have a HDR standard in DCI, but that we will live with a couple of proprietary standards and custom mastering.

- Carsten

[NocioSolo]

Thanks for the reply.
So, in your opinion, is the conversion of the HDR still too complex (and useless in my case)?
I have read about programs and plugins that can make this conversion, to the best of their ability, in real time giving the possibility to enjoy 4k HDR content even on non-HDR screens (madVR, MPV, ...); do you think this conversion can be used to generate a readable file for DOM that contains as much information as possible?
I would hate to give up so quickly, even if it's more than two weeks that my computers work as slaves to encode possible solutions...

[Carsten]

You may find tools that convert UHD material to common media files, but after that, they are SDR, not HDR anymore. Of course you can convert these to DCP with DCP-o-matic, but I am sure that converting or showing a standard bluray of the same title will show the better overall quality. You will probably also see a better quality when you play the original UHD media on an UHD player with it's output configured to SDR presentation. In that case, the player performs the intended HDR->SDR conversion based on grading decisions made during the mastering. It may be that at some time, tools will be available to perform a direct HDR->12Bit DCP XYZ mapping. Maybe Carl is interested in doing this, but, there clearly is a lack of content (hence interest) for this application, I assume. If you can supply a short snippet of UHD content, Carl may have a look. Reading HDR/UHD, however, will be a feature of the underlying FFMPEG framework. If HDR files can be made accessible through FFMPEG, then Carl should be able to use the additional information for encoding.

Keep in mind, cinema projector peak brightness is even below that of typical consumer SDR tv screens. Therefore, it makes little sense to show UHD content on typical DCI projectors.

- Carsten