More > JRiver Media Center 31 for Windows
SDR to HDR (Inverse Tone Mapping)
bogdanbz:
--- Quote from: Hendrik on May 28, 2023, 05:13:01 pm ---Inverse tone mapping is not something JRVR will ever offer, because a simple one-size-fits-all value for something like that is never going to yield any reasonable results. Converting SDR to a reasonable HDR requires a proper mastering step, not setting some value and hoping it comes out ok.
Enabling "direct mapping" would be relatively easy in comparison, but its not something i'm looking to do right this time.
--- End quote ---
My main issue with the SDR to HDR conversion is viewing SDR extras on UHD BluRays, to be honest.
I have Windows HDR turned off by default in Windows, and when I start playback of a UHD BluRay JRVR automatically turns Windows HDR mode on, which is great!
But when I start playback of a SDR extra on that BluRay from the BluRay menu, JRVR does not turn Windows HDR mode off, it stays on, and the Windows sRGB to HDR10 PQ conversion takes place as far as I can see.
Would it be possible to turn off Windows HDR when playback of a SDR extra starts? This would allow the TV display to switch to its SDR mode and the video content would be rendered just as it should, and without any conversion done by Windows as well.
@jmone, most research done on how to mix SDR and HDR content to look fine together is done by those in broadcast, as they have streams shot both ways. There's info in the UltraHD Forum Guidelines (https://ultrahdforum.org/guidelines/) - check the Indigo Book, there are conversion LUTs defined for such workflows - and in the various ITU reports (https://www.itu.int/pub/R-REP).
The conversion LUTs from the NBC Universal workflows are hosted on GitHub here.
Hendrik:
I think it should actually attempt to do that right now, as it follows the stream metadata. But I don't believe I have tested with a Blu-ray.
I can also add direct mapping in the near future, as its basically just yet another brightness slider for the reference white (or get the desired level from windows, but being able to configure that for video is probably better). I forgot that what MS calls G22 is actually treated like sRGB.
bogdanbz:
It's indeed not switching Windows HDR mode off when watching a SDR extra on a UHD HDR BluRay.
jmone:
Thanks - FWIW, I do mix both SDR and LOG captured footage to create combined HDR footage using Resolves "Inverse DRT for SDR to HDR conversion" which does not require a LUT. I'm more in the ICT/OCT than the LUT camp for converting between colour spaces (thanks to Daria Fissoun, who literally wrong the manual on color mgt for Davinci).
I'm not sure if you have had a chance to look at the 3 samples I linked a couple posts back, but that shows what the "Inverse DRT for SDR to HDR conversion" process can do (warts and all).
The focus on Tone and Gamut Mapping has always been on scaling down HDR material to work well on SDR Displays. JRVR does a great job of this. I think as more and more displays are HDR there will be a desire to expand legacy SDR content to (faux) HDR. Just like we now scale lower resolution legacy material to (faux) UHD.
Hendrik:
--- Quote from: jmone on June 01, 2023, 02:46:47 am ---I think as more and more displays are HDR there will be a desire to expand legacy SDR content to (faux) HDR. Just like we now scale lower resolution legacy material to (faux) UHD.
--- End quote ---
But there is the rub - upscaling video, similar to upsampling audio, you don't really expect "new" high-frequency detail to be created when you upscale, rather just reproduce the original faithfully. The same could be said about creating new brightness levels that never existed. Is this a lamp thats supposed to have 10000 nits, or just a white piece of paper?
Maybe AI stuff can do that more reasonably in the future, but "naive" algorithms will always produce weirdness all around.
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