The Curious Case of “Fake” TV Led Dolby Vision and v1.1.60

There has been a lot of emphasis put on so called "Fake" TV Led Dolby Vision in recent months.

Usually TV Led DV involves two video signals, a base layer and an enhancement layer, being fed down HDMI simultaneously as an 8-bit RGB tunnelled signal with the display recombining the layers, processing the metadata and squirting the resultant 12-bit 4:2:0 signal onto the screen.

As we know, in these media players, the enhancement layer is not processed, but what is maybe not so well known, is that the metadata is also processed in the player in TV Led Dolby Vision.

This has led people to declare this to be "Fake" TV Led and I can fully understand why, but given how VS10 works on media players, it was a bit short sighted.

Dolby spec dictates that both the player and the display have to contain Dolby Composer, the bit that sticks all this together, and my argument has always been that it doesn't matter where the metadata gets processed, it all amounts to the same thing on the screen.

But there's another side to this that seems to have been missed in all the evangelising.

There's the matter of Display Management (DM) and Content Mapping (CM).

Display Management is another part of the Dolby decode process and dictates how and what metadata is processed and there are different versions defined in the EDID, ostensibly to do with the age of the display.

Content mapping happens in post production and defines what the metadata does to the picture dependant on the display capabilities, and there are two versions, CMv2.9 and CMv4.0.

CMv4.0 is way more sophisticated and if you’re interested, full information can be found on Dolby’s website.

CMv2.9 is used in UHD BluRay and both CMv2.9 and CMv4.0 (which uses a whole new set of enhanced metadata trims) is used commercially in online delivery.

CMv4.0 is fully backwards compatible with CMv2.9, so if the display doesn’t support CMv4.0, CMv2.9 trims are used instead.

And I’m willing to bet no-one would ever notice...


But....


So called “Fake” TV Led DV can process any current version of Display Management and therefore both versions of Content Mapping and it can output the result on ANY Dolby Vision display – it’s not restricted by DM version.

“True” TV Led cannot do this – it needs a display that supports the DM version and CM version and for older TVs this is a problem.

So because of all the fuss this has generated, we now have a setting to choose how to handle TV Led DV.


1. TV Led

This is how it’s always been done previously – The DV signal is sent in an RGB tunnelled 8-bit signal and converted to 12-bit at the display but the metadata (trims, tone mapping, blah blah blah) is processed in the player before it hits the display.

As I said above, this means, as an example, that CMv4.0 is processed if the file supports it and the result is displayed on any Dolby Vision TV – the TV does not have to support CMv4.0 for it to be used.

If you don’t give a monkeys about all this, this is the one to choose.


2. TV Led Metadata Bypass Auto

Again, the signal is an RGB tunnelled 8-bit one but this time the metadata is sent to the display for that to process – for the purists, this is probably the way to go although I’d be very surprised if you see any difference.

The problem here is that if your TV does not support DMv4 and therefore CMv4.0, then the metadata associated with that will be ignored and fallback to CMv2.9.

Rule of thumb - if your TV was made in or after 2020, you should be fine.

I mean, no biggie – it’s what you’d get out of a UHD BluRay player after all.


3. TV Led Metadata Bypass with CMv4.0 forced

This is the same as #2 above but CMv4.0 is forced regardless of what the EDID says.

You have to be careful with this one and be sure you know what you’re doing and please note that this will not enable CMV4.0 support on a TV that doesn’t support it and could in fact be detrimental to the picture in that case.

This mode is only for people with a TV that supports CMv4.0 and are using a custom EDID that does not support CMv4.0.

Read that last bit again.

 

Great explanation Mark - thanks.

I've tried LLDV, TV-Led and TV-Led Metadata Bypass Auto on my 2024 LG G4. TBH I can't see a difference in any of them lol. Maybe I have shite eyes but to me all look great.

 

Nope, wouldn't expect you to

 

Speaking of these new settings, yesterday I carried out some tests watching The Meg in 4k DV and I encountered problems managing the motion control of the frames: first I watched the film with the LED TV setting and everything was fine. Then I set TV LED METADATA BYPASS AUTO and, watching the film again, I noticed that the motion control of the frames was managed worse and occasionally there were even stutters. I set it back to LED TV and the motion control handling was back to normal without any stuttering.

 

Haha! I've just had laser treatment applied on the capsules that support the artificial lenses in my eyes after Cataract Surgery a few years ago and have been able to see stuff so clearly this past week or so!!! Contrast and Colours much much better than before. So this subject really appeals to me. I shall be experimenting tomorrow as my hands are full with other things all day today.

 

Sony A95L , I should use CMV 4.0 or TV-led auto?

 

I have a Samsung TV and obviously I don't have DV, and I can confirm that the visual improvement in update 1.1.60 is very, very good. When I received the z9x 8k I didn't see much difference compared to the zidoo z9x I had, but with this update everything has changed, it looks spectacular in HDR, in sdr I don't notice that much difference.

 

I tried all options..and they all look great.
I love settings

 

Lol - I hate them cos I can never remember what they should be set to if things go t**s up cos I never write 'em down - don't start me on wiring!

 

You should read the first post again.

 

Big thanks to Mark for all the explanations.

 

Cheat sheets are an engineer's get out of jail card - always write stuff down.

And wiring - take pictures! I wish I'd had an iphone when I was out doing installs...

 

I did , CMv4 forced works for me on my TV without any issues.

 

Are you using a custom EDID?

 

Not yet, which is where my doubt was as the description in the player says one has to use it for forced CMv4. You have one I can try ? Picture quality in all settings look equally good right now. I can’t tell a difference so far . But I haven’t really spent much time on each setting.

 

Your TV supports CMv4.0 and you're not using a custom EDID, therefore it doesn't need forcing.

 

So auto is good I suppose.

 

Yes.

In all honesty, I'm being a bit pedantic - all three modes will work correctly with a TV that supports CMv4.0, but it's bad practice to force it when it's not needed.

That's why I wrote "Read that last bit again" at the end - to try to get people to understand why that option was provided.

 

I understand it clearly now , apologies, I am in the dyslexia spectrum some wordings confuse me, my brain gives me a bunch of varying interpretations.

 

Don't worry, and absolutely no need to apologise - Dolby Vision is an almighty cluster f**k these days and quite honestly I think we'd all be better off if just disappeared overnight.

I was just having a rant at @Sledgehamma about this - Dolby Vision started out with such noble intentions but, like THX before it, has just turned into a huge marketing machine. We'll have Dolby Vision air fryers before we know it....