What is the point of having the Zidoo pass through MaxFALL metadata for HDR10? MaxCLL makes sense.

As the title states, as far as I know, TVs don't do anything with MaxFALL metadata for HDR10. They definitely use maxcll/maxdml metadata, but not maxfall. Just curious what the point of having the maxfall pass through is?

@Markswift2003 I think this is likely a question for you

 

Some displays used MaxFALL and MaxCLL, some just use MaxCLL and some even use MaxMDL instead.

 

Thanks Mark. Just because I'm curious, do you know of an example of a display that uses MaxFALL? As far as I know, LG OLEDs only us MaxCLL and MaxDML?

Also bonus question, does Zidoo pass through MaxDML as well? It seemed to when I tested it...even though the option only says maxcll/maxfall.

Thank you sir!

 

As far as I know LGs do do it, but I don't have one so can't say for sure. Manufacturers never post such info so without TVs to test there's no way to know. obviously the likes of Sony and Panasonic PVMs do it...

I'd assume most manufacturers have got their act together now - there was a lot of confusion in the early days about what the metadata did and what the display should do with it but not these days.

Yes, the Zidoo passes MDL regardless of the position of the MaxCLL/FALL switch.

I always thought that switch was rather superfluous and confusing and it's been removed on the 1619BPD models so values are passed by default as they should be.

 

You're saying LGs use MaxFALL metadata? I'm pretty sure they just use maxcll/maxdml.

 

No, I said "As far as I know LGs do do it, but I don't have one so can't say for sure"

But as a simple answer to your original question:

Every other 4K HDR STB and UHD BluRay player does it, so why wouldn't it. If the display uses it, great, if not, who cares?

 

By "does it," do you mean passes through that metadata? If so, sure, yea. But do they actually "use" MaxFALL?

I'm being told that the Zidoo can't pass through MaxDML metadata because "It cannot pass through MaxDML because again there's no protocol to do it either via HDMI or DisplayPort." Is this wrong?

Also, I really do not think ANY tv actually USES maxfall. What would it use it for? Why would the TV want to apply a filmic tonemap to somethiing that's already filmic tonemapped? I'm not sure that makes sense. Would you be able to explain if I'm incorrect?

I'm not sure why you're asking me "who cares?" I care. I'm trying to understand how this all works. It's a hobby of mine and very interesting. So I'd like to know!

 

Yes, that's nonsense, of course it does - it's in the SEI message.

In combination with MaxCLL, MaxFALL is probably the most useful number because it gives an average.

Take this example from a recent commercial release :

Max/Min MDL: 4000 / 0.005 nits
MaxCLL/FALL: 1040 / 425 nits

MaxMDL is an utterly meaningless figure. If accurate, it just means the movie was probably graded on a Dolby Pulsar.

No, that doesn't make sense. A tone map is only needed with content with PQ gamma when the display cannot match the content luminance. A tone map cannot be "filmic", it's absolute. With a lot of modern TVs and most content, tone mapping isn't even needed these days.

 

Thanks for the answers. I guess I'm just confused on what a STB/Bluray Player/TV would actually DO with MaxFall. Like how would it be used with tonemapping? That's my question. I know many devices do pass through and include MaxFall but I don't understand what it is used for asides from just having extra information about a content's average brightness, ya know? I know MaxFall is used for Dolby Vision (so probably used both for TV Led and LLDV), but not sure how it's used for HDR10? I hope my question makes sense.

 

Tone mapping is only needed if the display can't reach the maximum luminance of the content, and in that case a tone map rolls off the EOTF early to match the display capabilities. In other words, the gamma curve is compressed to "fit" the display luminance. That's all a tone map is - it's nothing special or clever - it's just a gamma curve that's rolled off at the top.

Because HDR10 is static, the only thing a display has to go on is the metadata. The Mastering Display Min/Max luminance are of no consequence. You can grade content with MaxCLL of 100nits on a 4000nit Pulsar, but what relevance is that number to the content? None.

The content level is - and that's where MaxFALL and CLL come in - the level of roll off in the gamma curve and the point at which it starts rolling off should be calculated from both these values.

But to be honest, HDR10 is such a broad brush and content within one presentation so varied, that it doesn't really matter. In practice, one gamma curve would probably do for everything (more or less) and most people wouldn't notice, so that's why some manufacturers cheat - it's far easier to apply paint with a big brush than a small pointy one.

MaxFALL/CLL are not relevant to Dolby Vision - Like HDR10+, that uses dynamic metadata per scene or occasionally, per frame. Also, dynamic tone mapping doesn't need it either because it samples the actual video rather than relying on metadata.

Don't know why you've got such a downer on MaxFALL

 

Ok - here's another way to look at it (I'm using the term "brightness" here somewhat incorrectly just to keep it simple)

MaxCLL is the brightness of the brightest pixel in the movie.

MaxFALL is the brightness of the brightest frame in a movie.

Think of gamma as simply input vs output brightness.

We need to know MaxCLL so we know what's at the very top of the gamma curve, but we know we won't hit it very often.

We need to know MaxFALL to give us a starting point where the gamma curve starts to roll off towards the value at the top.

MaxFALL isn't the actual value where the gamma curve rolls off but it gives us that point because we want MaxFALL somewhere between the two.

Now we can design a gamma curve where the roll off minimises the compromise between dynamic range and overall brightness due to the display's deficiencies and we can call it "tone mapping" to sound super cool.

 

Thanks. I appreciate you taking the time to type this all out.

I'm not a downer on MaxFALL! I understand its importance and how it SHOULD be used for tone mapping. I'm just saying in practice it appears that literally NOTHING using MaxFALL aside from maybe some video players (maybe?), because:

1. PC games do not appear to use MaxFall/MaxFFTML metadata whatsoever. Apparently the PS5 uses it from an internal panel spec database but not seeing any evidence of it used on PC

2. Video players themselves on PC don't even seem to use this

3. TVs themselves don't even seem to use this to do static tonemapping. LG's 100% do NOT use Maxfall. They use maxcll and maybe also maxDML. Also almost positive Sony and Samsung do not use Maxfall. They use maxcll and/or maxdml as well.

That's all I'm saying. That in practice nothing seems to use MaxFall/MaxFFTML asides from maybe the PS5 (from its own database lookup), and maybe MPC/MPV or something? I don't even think they do. It seems like whatever purpose MaxFall is supposed to play for tone mapping, it's normally not taken advantage of and just straight up ignored.

 

I'm not sure why you think that "in practice nothing seems to use MaxFall".

In the early days when no-one really understood the technology there were some terrific clangers dropped - content released with MaxMDL at 10,000nits when there wasn't even a 4000nit display available at the time. Content released with MDL data only and no MaxCLL/FALL values.

I know my old Samsung uses MDL only. Nuts!

My JVC doesn't use anything!! Nuttier!

At some point, for some reason, people started referring to Min/Max Mastering Display Luminance as Min/Max Luminance, which is incredibly stupid and just plain wrong.

But in these enlightened days HDR is well understood - it's not the black art it was back in say 2015, so my assumption is that at least some TV manufacturers know what they're doing and I assume LG do it right because they're the only ones that Dolby recommend as a "Preview" monitor for real world testing after Post.

But regardless, any HDR10 source (STB, Disc player or whatever) will pass these values in the SEI because, well, it's in the SEI!! The Zidoos are a bit unique in that you can block them if you want but I've no idea why you'd want to do that.

Viva MaxFALL!!

 

By the way - MaxFFTML.

Made up gaming nonsense related to the display and of no relevance here.

 

Because nothing does? Lol. I know that devices pass through this metadata, but nothing actually makes use of the metadata to apply tonemapping. LG TVs do NOT use MaxFall. You can pass through MaxFall to the TV but it won't do anything with it. It only cares about MaxCLL and MaxDML. That's what I'm saying!

 

On what evidence?

 

The evidence is that I have LG panels, I've talked to people with LG panels. I've talked to people with Sony/Samsung panels. I've talked to multiple game developers. We all failed to find a single example of a game/tv/box/wahtever that uses it, aside from the PS5's internal database (it's apparently ACTUALLY HGIG compliant somehow?)

I mean.....do you have an example of something that uses it?

 

Fair enough. We can forget about MaxFFTML for now

 

Also, just in case it wasn't clear, I appreciate the conversation. I don't mean to come off as saying you're wrong or anything. I'm just trying to learn and figure stuff out. I don't doubt that I could be wrong.

 

@Markswift2003 Also, just in case it wasn't clear, I appreciate the conversation. I don't mean to come off as saying you're wrong or anything. I'm just trying to learn and figure stuff out. I don't doubt that I could be wrong.

I just have yet to find a single solid example of something using MaxFALL metadata to tone map, aside from the PS5 thing.