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 > Announcements and Chat > General Discussion

Reply
 
Thread Tools Search this Thread Display Modes
Old 3rd December 2023, 16:39   #381  |  Link
ErazorTT
Registered User
 
Join Date: Mar 2003
Location: Germany
Posts: 206
Quote:
Originally Posted by wswartzendruber View Post
The objective with incorporating Oklab is to say: "The HDR10 grading represents some artistic intent. That intent should be preserved as the exposure is adjusted to increase reference white."

RGB is not perceptually uniform.
Yes, but you're increasing the brightness for the reason to match the total brightness of the HLG stream to that of the SDR stream.

So I think it would be best if you compared these with the SDR stream to see which of these better match the blacks.
RGB: https://youtu.be/XMdFweclflY
Oklab: https://youtu.be/9hqkMBvwqSc
ErazorTT is offline   Reply With Quote
Old 3rd December 2023, 18:53   #382  |  Link
ErazorTT
Registered User
 
Join Date: Mar 2003
Location: Germany
Posts: 206
I tested the v2.0.0.b2 against the v1.1.0, and I am seeing exactly no differences, apart from rounding to +/-1 at 10 bits. And I scrolled through the whole movie. What am I missing?
Here is my script:

Code:
LoadPlugin("C:\...\dgindexnv\DGDecodeNV.dll")
pq=DGSource("C:\...\pq.dgi")

pq=pq.z_ConvertFormat(chromaloc_op="top_left=>center",width=pq.Width()/2,height=pq.Height()/2,pixel_type="RGBP16",colorspace_op="2020ncl:st2084:2020:limited=>rgb:st2084:2020:full",dither_type="none",resample_filter="spline36",resample_filter_uv="spline36")
hlg1=pq.Cube("C:\...\1.1.0\lut_2.75_1000.cube")
hlg1=hlg1.z_ConvertFormat(chromaloc_op="center=>top_left",pixel_type="YUV420P16",colorspace_op="rgb:std-b67:2020:full=>2020ncl:std-b67:2020:limited",dither_type="none",resample_filter="spline36",resample_filter_uv="spline36")
hlg2=pq.Cube("C:\...\2.0.0.b2\lut_1.4_1000.cube")
hlg2=hlg2.z_ConvertFormat(chromaloc_op="center=>top_left",pixel_type="YUV420P16",colorspace_op="rgb:std-b67:2020:full=>2020ncl:std-b67:2020:limited",dither_type="none",resample_filter="spline36",resample_filter_uv="spline36")

StackVertical(hlg1,hlg2,Subtract(hlg1,hlg2))
ConvertBits(10,dither=0)
The v1.1.0 lut was created with that command:
./pq2hlg.exe lut_2.75_1000.cube --max-cll 1000 --lum-scale 2.75 --size 65 -c

The v2.0.0.b2 lut was created with that command:
./pq2hlg.exe lut_1.4_1000.cube --max-cll 1000 --exposure 1.4 --size 65

I came to the lum-scale and exposure by comparision to my SDR source.
Please create lut files using the parameters above with 1.1.0 and compare them yourself against 2.0.0.b2.

Last edited by ErazorTT; 3rd December 2023 at 20:09.
ErazorTT is offline   Reply With Quote
Old 4th December 2023, 06:11   #383  |  Link
wswartzendruber
hlg-tools Maintainer
 
wswartzendruber's Avatar
 
Join Date: Feb 2008
Posts: 401
Here's a screenshot comparison. The bottom two are done with 2.0.0-beta2.











Regarding LUT comparison between 1.1.0 and 2.0.0-beta2, if your source was monochrome, there might not be a difference at all. If Oklab is to be believed, scaling linear brightness by a fixed factor is perceptually uniform, so long as no color (non-D65) is involved. This, at least, is what I found when I experimented with it.

But when color is involved, things change. Here's line 168,269 from each one:

1 1 0.9537389

1 1 0.94303465

Or line 39,788:

0.008232022 0.66472024 0.10244914

0.01649015 0.6643379 0.102354646
wswartzendruber is offline   Reply With Quote
Old 6th December 2023, 02:04   #384  |  Link
ErazorTT
Registered User
 
Join Date: Mar 2003
Location: Germany
Posts: 206
Quote:
Originally Posted by wswartzendruber View Post
if your source was monochrome, there might not be a difference at all.
Crap, yeah it was monochrome, because I was interested in the brightness side of things. Ok so I will retry with color.
ErazorTT is offline   Reply With Quote
Old 7th December 2023, 04:06   #385  |  Link
wswartzendruber
hlg-tools Maintainer
 
wswartzendruber's Avatar
 
Join Date: Feb 2008
Posts: 401
Awesome, that probably explains things, then.

Remember that if no reference white adjustment is needed, both versions should generate identical LUTs.
wswartzendruber is offline   Reply With Quote
Old 10th December 2023, 05:24   #386  |  Link
wswartzendruber
hlg-tools Maintainer
 
wswartzendruber's Avatar
 
Join Date: Feb 2008
Posts: 401
Here's 2.0.0-beta3.

This corrects SDR black and white previews. Those were using BT.2020 coefficients earlier in beta2.

EDIT: That is, taking a black and white preview shot of a BT.709 Blu-ray now uses the BT.709 conversion matrix to go to Oklab for better brightness assessment.

Last edited by wswartzendruber; 11th December 2023 at 05:02.
wswartzendruber is offline   Reply With Quote
Old 22nd December 2023, 03:39   #387  |  Link
wswartzendruber
hlg-tools Maintainer
 
wswartzendruber's Avatar
 
Join Date: Feb 2008
Posts: 401
In today's segment of Useless Trivia™, The Fifth Element declares a MaxCLL of 10,000 nits. These levels can be seen on the tiny lights highlighting the aliens's armor at the beginning of the movie.
wswartzendruber is offline   Reply With Quote
Old 22nd December 2023, 11:51   #388  |  Link
FranceBB
Broadcast Encoder
 
FranceBB's Avatar
 
Join Date: Nov 2013
Location: Royal Borough of Kensington & Chelsea, UK
Posts: 2,836
Quote:
Originally Posted by wswartzendruber View Post
In today's segment of Useless Trivia™, The Fifth Element declares a MaxCLL of 10,000 nits. These levels can be seen on the tiny lights highlighting the aliens's armor at the beginning of the movie.
LOL making something no one can see, including the ones who actually created it, cool xD
I guess this is their way of saying that their Pogo Stick is bigger than everyone else's... but it's not.

(it's a Modern Family reference, go look it up if you didn't get it).
FranceBB is online now   Reply With Quote
Old 22nd December 2023, 22:26   #389  |  Link
wswartzendruber
hlg-tools Maintainer
 
wswartzendruber's Avatar
 
Join Date: Feb 2008
Posts: 401
I used Oklab to push the peak brightness down from 10,000 nits to 100 nits, but otherwise did no tone mapping:

wswartzendruber is offline   Reply With Quote
Old 23rd December 2023, 19:56   #390  |  Link
ErazorTT
Registered User
 
Join Date: Mar 2003
Location: Germany
Posts: 206
Another question converning v2. How come that the -c parameter is not needed anymore? Is this due to the oklab processing?
ErazorTT is offline   Reply With Quote
Old 23rd December 2023, 20:38   #391  |  Link
wswartzendruber
hlg-tools Maintainer
 
wswartzendruber's Avatar
 
Join Date: Feb 2008
Posts: 401
Quote:
Originally Posted by ErazorTT View Post
Another question converning v2. How come that the -c parameter is not needed anymore? Is this due to the oklab processing?
No. It's that I decided it was dumb.

-c was in 1.x because HLG has limits on how much value a single color channel can have when the other two channels aren't present. Ergo, the maximum value a single color channel can have increases as the other two channels accompany it. The only time R, G, and B can be at their max is when all three are at their max.

-c worked by saying, "I've got a red channel by its self calling for 262 nits, but I can only take this to 201 nits with HLG. I'm going to divert some of the overall signal strength from this red channel to the other two. Saturation will be lost but overall brightness will be preserved."

Except that not even that is true, because linear RGB is a terrible predictor for perceptual brightness.

Note that HLG allows isolated channels to go high enough that this shouldn't even be something anyone runs into.

EDIT: This is discussed in BT.2408-4 page 25, in section 6.5

Last edited by wswartzendruber; 23rd December 2023 at 20:42.
wswartzendruber is offline   Reply With Quote
Old 24th December 2023, 13:09   #392  |  Link
ErazorTT
Registered User
 
Join Date: Mar 2003
Location: Germany
Posts: 206
Ok I see. Since you mention BT.2408-4, please be also aware that the current release is now already at BT.2408-7.

https://www.itu.int/dms_pub/itu-r/op...2023-PDF-E.pdf
ErazorTT is offline   Reply With Quote
Old 24th December 2023, 19:01   #393  |  Link
wswartzendruber
hlg-tools Maintainer
 
wswartzendruber's Avatar
 
Join Date: Feb 2008
Posts: 401
Quote:
Originally Posted by ErazorTT View Post
Ok I see. Since you mention BT.2408-4, please be also aware that the current release is now already at BT.2408-7.

https://www.itu.int/dms_pub/itu-r/op...2023-PDF-E.pdf
Oh for crying out loud. I wanted to release 2.0.0 on New Year's Day.

But I should examine this first.

EDIT: Okay so they have made an attempt to address the issue of linear RGB scaling. They're clarifying how two separate adjustments can be made, one to RGB and then the other to Y. And they're attempting to get more perceptually accurate color modeling using data from BBC and ARIB surveys. Converting from RGB to Oklab, scaling, and then converting back to RGB is going to be more expensive, but the LUT only needs to be generated once. And whereas BT.2408-7 only covers scaling from SDR to HDR, Oklab can (theoretically) scale to and from any brightness. Oklab has been modeled using an extensive data set from color perception surveys.

So I'm currently planning to leave Oklab in place for 2.0.0. I would need someone to tell me that Oklab scaling looks bad on a high-end grading monitor (which I don't have).

I need to just shell out the money on an Asus ProArt monitor.

Last edited by wswartzendruber; 24th December 2023 at 19:47.
wswartzendruber is offline   Reply With Quote
Old 24th December 2023, 23:37   #394  |  Link
ErazorTT
Registered User
 
Join Date: Mar 2003
Location: Germany
Posts: 206
Quote:
Originally Posted by wswartzendruber View Post
I would need someone to tell me that Oklab scaling looks bad on a high-end grading monitor (which I don't have).
Anything specific to look out for? What would be the critical places in the LUT? I have a LG EP950, which has 33 point 3D hardware calibration and has the same JOLED display as the OLED ProArt.
ErazorTT is offline   Reply With Quote
Old 25th December 2023, 06:13   #395  |  Link
wswartzendruber
hlg-tools Maintainer
 
wswartzendruber's Avatar
 
Join Date: Feb 2008
Posts: 401
Quote:
Originally Posted by ErazorTT View Post
Anything specific to look out for? What would be the critical places in the LUT? I have a LG EP950, which has 33 point 3D hardware calibration and has the same JOLED display as the OLED ProArt.
Find something that needs a lot of correction (stress test). Some of the 20th Century Fox stuff is graded really dark placing reference white at 48 nits. Alita is one such movie. If you find a movie like that, try this command with both 1.x and 2.0.0-beta3:

pq2hlg -m 162 -r 48 -s 128 pq2hlg.cube

The 2.x LUT should look a lot more like an exposed representation of the original than the 1.x. You may specifically find that hue changes with 1.x and the midtones might be overexposed.

Basically, 2.x should just look like a brighter take on the original while 1.x looks off.
wswartzendruber is offline   Reply With Quote
Old 25th December 2023, 21:01   #396  |  Link
ErazorTT
Registered User
 
Join Date: Mar 2003
Location: Germany
Posts: 206
I really don't understand why you see differences between the new and the old LUTs. I don't see any.

Please take a look at the script here. It generates a calibration pattern, then transforms it using the old and the new LUT, and then compares the outputs. There arn't any differences. Looking at the calibration pattern, I would have thought that there should be differences.

Thats the script:
https://drive.google.com/file/d/1dSv...usp=drive_link

Thats the calibration pattern the script generates which then gets transfomed by the LUTs:


To use the scirpt you need to generate the LUT files and adapt the paths to the LUT files at the very bottom of the script.
ErazorTT is offline   Reply With Quote
Old 26th December 2023, 03:44   #397  |  Link
wswartzendruber
hlg-tools Maintainer
 
wswartzendruber's Avatar
 
Join Date: Feb 2008
Posts: 401
Sweet Fancy Moses. You're right. I have no idea how or why, but 1.1.0 and 2.0.0-beta3 produce visually identical results despite the large differences seen in the previous page.

I'm investigating...

EDIT: So far, scaling linear RGB by a factor, and scaling Oklab by a much smaller factor.............produce the same results. This shouldn't be the case at all. Not even close... This also doesn't explain the differences on the previous page.

EDIT: Increasing image exposure via linear RGB appears to be "correct" for now anyway. Oklab does return different brightness levels when monochroming an image (like in preview mode).

EDIT: Okay, so...

1. Linear RGB may not be perceptually uniform, but it still suffices for increasing image exposure.
2. 2.0.0 should simply revert to using linear RGB for exposure (reference white) adjustments.
3. Oklab still has a place in black-and-white preview mode (which can be used to determine exposure).
4. YouTube has likely changed the way BT.709 is generated from HLG uploads, explaining the differences on the preview page (uploaded a year apart).
5. Be more thorough in monitoring differences (this has bitten me in the ass before).

EDIT: I grabbed a HDR Windows machine and screenshot the two YouTube clips with HLG playback. They appear to have identical levels.

Last edited by wswartzendruber; 26th December 2023 at 17:31.
wswartzendruber is offline   Reply With Quote
Old 28th December 2023, 22:24   #398  |  Link
wswartzendruber
hlg-tools Maintainer
 
wswartzendruber's Avatar
 
Join Date: Feb 2008
Posts: 401
Titanic (which just came out on 4K) declares a MaxCLL of 283 nits.
wswartzendruber is offline   Reply With Quote
Old 29th December 2023, 09:18   #399  |  Link
FranceBB
Broadcast Encoder
 
FranceBB's Avatar
 
Join Date: Nov 2013
Location: Royal Borough of Kensington & Chelsea, UK
Posts: 2,836
Well, that's in line with other UHD re-scanned movies like Goodfellas which declares 247 Nits.
To think that it was only a few years ago, in 2016, when I've got the Apple ProRes FULL HD re-scan and encoded an XDCAM-85 out of it (back when the "XDCAM SHD - aka Super HD" slogan was still a thing 'cause Sony didn't know how to cope with newer and better 10bit standards so they just reckoned they could push more bitrate into a dying MPEG-2 8bit standard to go from 50 Mbit/s (XDCAM-50) to 85 Mbit/s (XDCAM-85) totally missing the point about the issues MPEG-2 had and its problems with banding etc.
Anyway, I remember that day as if it was today, it was a weekend, Sunday morning, in 2016, I was at work and given that the last time I watched Titanic was back when DVD were a thing, I re-watched the entire movie in XDCAM-85.
I went into one of the QC rooms at Sky, the QC Room 3, at the third floor, 'cause we had one and only one Harmonic Omneon playback port capable of playing XDCAM-85 files (all the other VS7 ports were only capable of up to XDCAM-50) and watched it.
Aside from a few places in which the film was clearly ruined, the overall picture was rather sharp but it had plenty of grain.
Back then I thought "this is amazing" 'cause I could see way more details than the ones I remembered on the DVD, although there were a few scenes with water that presented banding anyway (despite all the grain) and I clearly thought "why is the world sticking with MPEG-2 8bit? why?!".

Well, fast forward to 2023, 7 years later, and we have the 4K Remaster where they probably re-scanned the old film once again.
At this point I'm curious to see that one as well and see whether there are effectively more details compared to the FULL HD scan or if it's just more grain like in Goodfellas.
If I get my hands on it, I'll be back with a few screenshots.
The only thing I don't understand about those Remasters, though, is the fake PQ 'cause no matter how much you play around with it, the source will always be SDR (and in some case, even worse than 100 nits SDR, depending on the condition of the film). I mean, sure, you can bring some highlights up, mask some reflections and treat them differently etc but why?

Last edited by FranceBB; 29th December 2023 at 09:23.
FranceBB is online now   Reply With Quote
Old 29th December 2023, 18:15   #400  |  Link
wswartzendruber
hlg-tools Maintainer
 
wswartzendruber's Avatar
 
Join Date: Feb 2008
Posts: 401
Quote:
Originally Posted by FranceBB View Post
Well, that's in line with other UHD re-scanned movies like Goodfellas which declares 247 Nits.
To think that it was only a few years ago, in 2016, when I've got the Apple ProRes FULL HD re-scan and encoded an XDCAM-85 out of it (back when the "XDCAM SHD - aka Super HD" slogan was still a thing 'cause Sony didn't know how to cope with newer and better 10bit standards so they just reckoned they could push more bitrate into a dying MPEG-2 8bit standard to go from 50 Mbit/s (XDCAM-50) to 85 Mbit/s (XDCAM-85) totally missing the point about the issues MPEG-2 had and its problems with banding etc.
Anyway, I remember that day as if it was today, it was a weekend, Sunday morning, in 2016, I was at work and given that the last time I watched Titanic was back when DVD were a thing, I re-watched the entire movie in XDCAM-85.
I went into one of the QC rooms at Sky, the QC Room 3, at the third floor, 'cause we had one and only one Harmonic Omneon playback port capable of playing XDCAM-85 files (all the other VS7 ports were only capable of up to XDCAM-50) and watched it.
Aside from a few places in which the film was clearly ruined, the overall picture was rather sharp but it had plenty of grain.
Back then I thought "this is amazing" 'cause I could see way more details than the ones I remembered on the DVD, although there were a few scenes with water that presented banding anyway (despite all the grain) and I clearly thought "why is the world sticking with MPEG-2 8bit? why?!".

Well, fast forward to 2023, 7 years later, and we have the 4K Remaster where they probably re-scanned the old film once again.
At this point I'm curious to see that one as well and see whether there are effectively more details compared to the FULL HD scan or if it's just more grain like in Goodfellas.
If I get my hands on it, I'll be back with a few screenshots.
The only thing I don't understand about those Remasters, though, is the fake PQ 'cause no matter how much you play around with it, the source will always be SDR (and in some case, even worse than 100 nits SDR, depending on the condition of the film). I mean, sure, you can bring some highlights up, mask some reflections and treat them differently etc but why?
I've got one clip up so far:

Titanic: Rose Arrives in Southampton [HDR-HLG]

EDIT: If you want something up in the original PQ, I can do that too so long as it's kept under two minutes.

EDIT: Titanic: Ending [HDR-HLG]

Last edited by wswartzendruber; 29th December 2023 at 22:59.
wswartzendruber 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 23:45.


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