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29th July 2020, 04:07 | #1 | Link |
hlg-tools Maintainer
Join Date: Feb 2008
Posts: 413
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4K Blu-ray: Conversion from PQ to HLG
I have a Rust project that converts raw PQ frames into HLG. It follows the BBC R&D method for doing so and is quite primitive. I am contemplating extending it with the following approach:
1. Determine the reference white level of the movie by sampling how bright the credits are. * RGB48 (PQ, Rec.2020) comes in from FFMPEG. * 2. Globally adjust the brightness of each frame as a whole such that the credits (if white) sit at 203 nits (linear scaling of each color channel). 3. Apply Kim-Kautz tone mapping to push everything down to within 1,000 nits. 4. Apply the inverse HLG EOTF function. * RGB48 (HLG, Rec.2020) goes back out to FFMPEG. * Given that I want a Good™ HLG encode of something, does this seem like a good way to go about it? |
6th May 2021, 20:05 | #2 | Link |
Registered User
Join Date: Nov 2004
Location: Poland
Posts: 2,843
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Question is - why are you doing it? If you have optimal PQ master and about all TVs support HDR10 then what is the point going to HLG?
I see the point going to SDR, but going PQ<->HLG is somehow pointless. |
27th August 2021, 08:58 | #3 | Link |
Registered User
Join Date: Feb 2020
Posts: 541
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I recommend using constant luminance HLG. https://github.com/sekrit-twc/zimg/pull/78
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