Welcome to Doom9's Forum, THE in-place to be for everyone interested in DVD conversion.

Before you start posting please read the forum rules. By posting to this forum you agree to abide by the rules.

 

Go Back   Doom9's Forum > Programming and Hacking > Development

Reply
 
Thread Tools Search this Thread Display Modes
Old 19th October 2022, 10:22   #1  |  Link
Alexkral
Registered User
 
Join Date: Oct 2018
Posts: 328
Help with Quadratic Bézier

Hi guys, I'm trying to implement the gamut mapping method proposed in Annex 5 of ITU-R BT.2407-0 (pages 34-39). Here's the link:

https://www.itu.int/dms_pub/itu-r/op...2017-PDF-E.pdf

Previously, I've been using this same method without the soft clip part, I don't think the soft clip is going to make much of a difference, but at this point I'm just curious.

So I have everything working... except the curve. I admit I didn't know anything about Bézier curves before this, but now that I've learned a bit, the proposed formula doesn't seem to make any sense. The values ​​I get using it are clearly wrong, and I don't even know if the square brackets have a special meaning here that I don't understand.

In the algorithm steps on page 38, there are some errors as well. First, it refers to the source color as both C2100 and C2020, it doesn't matter since it's clear that both mean the same. So in step 6, it's clear to me that the function must be: f(W C2020 / W P709). This makes perfect sense, first because it uses C2020 for something, and second because this will map P2020 to P709 as explained. But anyway, W C2020 / W P709 is not going to be in the range (0,1) as it's supposed to be.

I think I could easily do some kind of different interpolation, even using a Quadratic Bézier now that I've learned how they work, but in order to do it as proposed, I thought it was worth asking first in case anyone notices what I'm missing.
__________________
AviSynth AiUpscale
Alexkral is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +1. The time now is 10:18.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.