[Help] Workflow for regrading UHD?

[LucasGodzilla]

I would love a guide on how to convert from a HDR UHD file to a 10bit intermediate codec for editing / grading, then back out of the NLE (Premiere) to a file for encoding (in x265 or similar).

Unless the HDR on the UHD is something fancy like Dolby Vision or HDR10+, it arguably can be handled like any other standard Blu–Ray media–wise (so you can just automatically dump the contents into a ProRes with your standard scripting of choice), except once you import it into a program like Da Vinci Resolve or Adobe, you would have to convert the color space from Rec.2020 ST2084 into whatever medium of your choice.

As mentioned in an earlier post, this is something that enters into the territory of color management, which is something you'd have to look into with your software of choice—as how tonemapping should be handled or previewing goes is primarily subjective.

Then, in theory, you'd export it like you would any other project, but you have to make sure the output is converted back to the initial Rec.2020 ST2084 space. It will look weird, but if you encode the file to x265 correctly, it should be detected properly by players and decode in HDR.

I recommend poking here to see how to handle that part specifically: x265 UHD-BD compliant "perfect" settings

Should note though that for the provided HDR settings, you might have to remove this flag (if memory serves right, it throws errors now because newer versions of x265 made it a default and removed the command)...

Code:

--no-temporal-layers

And on top of this, you will have to alter the following flag...

Code:

--transfer bt2020-10

And replace it with this for standard HDR detection...

Code:

--transfer smpte2084

In theory, the original flag would allow you to play Rec.2020 Gamma 2.4 outputs, but it seems to only work with VLC and is not detected on any other setup. The newer one utilizes the proper SMPTE2084 / PQ transfer for proper HDR with NIT peaks over 100.

That's the the most concise explanation I really can provide on the matter atm.

[Serums]

Thanks for the insight! I'll test this.