I Have Published a HDR10 to HLG Converter

[kolak]

Regardless how "strange" MaxCLL and MaxFALL are there is this as an alternative measure (taking into account overshoots problem:

https://postimg.cc/YvJVJCfW

[kolak]

Top and bottom bars (as separate files) give similar MaxCLL (just bit above 1000nits).
In the same time max Y is 475 vs 705, so very different and not really appropriate for MaxCLL calculation.



Grab is form QTX, so tone mapped to 500 nits Mac screen (irrelevant here).
Top row is just blue channel of the bottom bars.

This makes those metadata values defined in very confusing way, but I assume there is some idea behind them.
I've just learnt they are very different things than what I thought (even if I remembered them been defined in some specific way).

In the same time in Resolve scopes both peak at around 1000nits, so show up correctly. This means when I grade in Resolve (by scopes to 1000nits) MaxCLL should be 1000nits not more.
So I'm confused by numbers from those titles from the other thread. They should not be so "strange" and random. Very possible most of them have simply wrong values as metadata. Some do look fine though.

[wswartzendruber]

Originally Posted by kolak

Regardless how "strange" MaxCLL and MaxFALL are there is this as an alternative measure (taking into account overshoots problem:

https://postimg.cc/YvJVJCfW

Well hello there...

[quietvoid]

The whole article (image based): https://0x0.st/oSpl.pdf

[kolak]

Hmm...looks like original recommendation wasn't really well thought out. I'm still not very convinced with current formula either.

[wswartzendruber]

Originally Posted by kolak

Hmm...looks like original recommendation wasn't really well thought out. I'm still not very convinced with current formula either.

It's a bit late to be having this conversation, isn't it?

[kolak]

Why too late?
You can always change a formula
MaxCLL may stay as is, but I can see that companies started counting "titles' max brightness" in own ways- more intuitive/representative.
Also for your needs MaxCLL may be simply not the best measure.

[wswartzendruber]

If MaxCLL is retroactively reinterpreted to mean Y instead of maxRGB, television sets are going to suck at tome mapping.

[kolak]

They unlikely to change this, but you can ( if old way is not really representative).
Do TVs actually use it? Apparently many TVs don’t.

[wswartzendruber]

Originally Posted by kolak

They unlikely to change this, but you can ( if old way is not really representative).
Do TVs actually use it? Apparently many TVs don’t.

MaxCLL tells you how aggressively you need to tone map.

[kolak]

Unless TVs does it dynamically in realtime ?

[wswartzendruber]

Originally Posted by kolak

Unless TVs does it dynamically in realtime ?

@FranceBB: Do TVs really do this?

[FranceBB]

Yes, but only some brands and it really depends.
The idea was to cope with missing mandatory info.
Although those values are mandatory for PQ streams, a relatively high number of files spreading all over internet didn't have those and Samsung saw that coming.
To put this into context: I gave to the TV a PQ without metadata other than the fact that it was PQ BT2100 and the TV worked that one out surprisingly well.
When it comes to metadata actually being there, though, it's a different story and I found out that some manufacturers respect them and some other don't and do their thing anyway.
Again this is due to the fact that some of them are just wrong.
On the other hand, I did make a test by giving Samsung a PQ file that was artificially stretched to occupy all the available values from top to bottom and then I told the TV that it was 1000 nits (it wasn't). The result wasn't completely wrong in the sense that the TV did adjust something and recognised that something was wrong, but it still did a fairly poor job cause while some scenes were looking good, some others almost made me blind, especially when red was involved.
Still I'm pretty sure that some TVs do something to correct the result, but can still get it pretty wrong if the value is wrong.

And of course you'll never have any of those issues with HLG, which is also an added benefit of using it.

[Balling]

Originally Posted by wswartzendruber

@FranceBB: Do TVs really do this?

LG does it.

[kolak]

Looks like MaxCLL is big problem.
Some HDR ProRes444 master.
Supplied value (from master done in Flame)=997, measured in Resolve around 2800
MaxFALL is 172 vs. 171, so looks fine.

[wswartzendruber]

PQ: Overcomplicating consumer video since 2016.

[rwill]

Originally Posted by wswartzendruber

PQ: Overcomplicating consumer video since 2016.

PQ is good if its done right.

Not that CLL Info and Mastering Display is needed, but I wonder how people manage to continuously screw them up. And the idea that one can represent the characteristics of a whole sequence in just a couple of values also does not fit into my head.

[rwill]

Originally Posted by FranceBB

On the other hand, I did make a test by giving Samsung a PQ file that was artificially stretched to occupy all the available values from top to bottom and then I told the TV that it was 1000 nits (it wasn't).

PQ is an absolute range. You cannot re-scale it. You cannot just say that a 10k nits pixel is 1k nits. How would this even work anyway ?

[FranceBB]

Originally Posted by rwill

And the idea that one can represent the characteristics of a whole sequence in just a couple of values also does not fit into my head.

It doesn't, in HDR10+ you have it dynamically changing on a scene-per-scene basis and then of course you have all the crazy stuff with Dolby Vision dual layer 10bit layer 1 + layer 2 to create a dynamically changing 12bit HDR PQ video.

Originally Posted by rwill

PQ is good if its done right.

Sure, although it's gonna take a long time before people (I mean consumers) will be able to enjoy stuff over 1000 nits and as far as the argument of "added nits in the blacks as it's a totally logarithmic curve while HLG isn't", that's true, but only those who have OLED (or similarly capable screens) are able to notice the difference in the blacks and those who do have those are also limited to around 900 nits anyway due to the way those LED work, so...

[rwill]

Originally Posted by FranceBB

It doesn't, in HDR10+ you have it dynamically changing on a scene-per-scene basis and then of course you have all the crazy stuff with Dolby Vision dual layer 10bit layer 1 + layer 2 to create a dynamically changing 12bit HDR PQ video.

Yeah but no one was talking about HDR10+ or Dolby Vision. People talked about Content Light Level Information and how it affects HDR10 in televisions. My guess is that the HDR10 metadata is not needed at all for a television to be able to display PQ/2020 content 'correctly'. I only know of some use in Power Management where it can have benefits.

Originally Posted by FranceBB

Sure, although it's gonna take a long time before people (I mean consumers) will be able to enjoy stuff over 1000 nits and as far as the argument of "added nits in the blacks as it's a totally logarithmic curve while HLG isn't", that's true, but only those who have OLED (or similarly capable screens) are able to notice the difference in the blacks and those who do have those are also limited to around 900 nits anyway due to the way those LED work, so...

So its somewhat future proof instead of being a stop gap solution like HLG ?