Magic Lantern Forum

Using Magic Lantern => Raw Video => Raw Video Postprocessing => Topic started by: vastunghia on March 22, 2022, 01:34:11 PM

Title: HDR10+ workflow
Post by: vastunghia on March 22, 2022, 01:34:11 PM
Thought I'd share my current workflow for rendering HDR10+ videos. [EDIT 7-8 apr 2022 highlighted in red] [EDIT 28 apr 2022 highlighted in blue]

Battle plan

Requirements (apart from camera with ML of course)
* Even though this is far from optimal (I know!), and since I am just an amateur and not a pro, to grade in HDR I use my Samsung LED TV: I got a Blackmagicdesign UltraStudio Monitor 3G to connect it to my Mac, it costs ~100 bucks. Also, to use UltraStudio Monitor 3G, make sure you have a real Thunderbolt 3 cable, not just USB. And an HDMI cable which is at least compliant with specs 2.0a.
** On my Mac, I installed it using Homebrew, which is a very convenient way to get it.

Detailed workflow

Happy to receive feedbacks, comments and suggestions.

Thank you

Sergio
Title: Re: HDR10+ workflow
Post by: timbytheriver on March 22, 2022, 02:02:36 PM
Thanks for sharing this detailed info Sergio.

I've been experimenting with HDR10+ for awhile also, and share much of the same workflow, except that I use Hybrid instead of FastFlix for muxing the json file into the H265 file.

I find it frustrating that although HDR10+ is supposedly open-source, we cannot yet gain access to the trim controls in DaVinci Resolve. This means that DR is writing some strange arbitrary nit metadata which makes it almost impossible to judge what is happening when we compare an x-nit target with a y-nit target display. e.g. Though my Panasonic TV is HDR10+ and displays the label when I view exports – I cannot see any different tone-mapping happening from straight HDR10. I suspect this maybe because my display is already close to 1000nit anyway – so I'm guessing that the metadata changes are not being required.

Do you have a similar experience?

The only way so far of getting access to HDR10+ trim controls is via hyper-expensive mastering apps like Transkoder – or a slightly less pricey solution here: https://ff.de/products/ It's a bit of a bar to users wanting just to dip their toe in the HDR10+ eco-system!

I posted a question along these lines to the HDR10+ Technologies people on this video, but there are no replies yet.  ::)

Title: Re: HDR10+ workflow
Post by: vastunghia on March 22, 2022, 06:33:03 PM
Hi Tim,

thanks for your comments! You are definitely a few laps ahead on HDR10+ ;)

Yes currently the HDR10+ trims are applied on the basis of a black box by DVR, and cannot be changed... not exactly sure I would be able to obtain better results via manual settings though, to be honest. But yes, pretty weird that there is no possibility to change them.

I too will need to experiment to see if same HDR10 footage with and w/o HDR10+ metadata looks different on my entry-level LCD TV (~ max 550 nits). Also, not clear to me whether I should keep 'Enable Tone Mapping Preview' enabled during grading. Is DVR trying to simulate how my final rendered video will show on my TV with HDR10+ metadata? And if so, is it reliable? What I see for sure is that enabling it has the effect of lowering overall luminosity a little bit, in my case.

More experiments needed for sure...

S
Title: Re: HDR10+ workflow
Post by: timbytheriver on March 23, 2022, 10:02:11 AM
Also, not clear to me whether I should keep 'Enable Tone Mapping Preview' enabled during grading. Is DVR trying to simulate how my final rendered video will show on my TV with HDR10+ metadata?
This is the theory I believe. In practise I believe it's still work in progress.  ::)

Another unknown to factor-in is the TV's own tone-mapping when it gets near to its max-nit value. Each TV manufacturer has its own black-box to achieve this. So how exactly DVR can accurately simulate this remains to be seen.

My experiments were so frustrating because I never saw any noticeable changes with/without HDR10+ metadata. After this I lost heart in testing further!  :( Maybe you will fare better since your target display max-nit level of ~550 is a better test case for metadata control  – if you are grading say to 1000nits max. The rule of thumb seems to be that the nearer the target display is to the max grading nit level – the reduced need for metadata to produce a 'roll-off'. And if the TV is doing this anyway – what's the point of the metadata at all? So many questions!

This guy's channel has some very informative info on HDR10+ https://www.youtube.com/channel/UCyzCqHyxr0uIF3eVFc9KPEQ

We can though all agree that Magic Lantern files are capable of out-puting excellent source material for HDR!  :)



Title: Re: HDR10+ workflow
Post by: vastunghia on April 07, 2022, 02:06:03 PM
Stumbled upon a weird behavior of DVR today, as I realized that it was not embedding correct HDR10 metadata (MaxFALL in particular) in another video project I was working on. The exported .hdr10 file read MaxFALL = 659, but the DVR-rendered ProRes video had 400 (which appears to be DVR default value) according to MediaInfo.

HEVC encoding of the ProRes master with x265 did not help even when passing x265 the –max-cll “1000,659” option, as for some reason the input ProRes master file metadata (400) was passed on to the output HEVC rendered file, regardless of my specific use of the -max-cll option.

So I had to figure out a way to fix this in the rendered HEVC file, and I think I succeeded. Details in the first post.

Sergio

Ps: still need to investigate whether the inclusion of HDR10+ metadata does add anything to visual experience vs plain-vanilla HDR10 metadata on my 550-nit capable TV. Hope to find the time soon.
Title: Re: HDR10+ workflow
Post by: vastunghia on April 07, 2022, 09:22:34 PM
...and I still don't get exactly how the HDR10+ grading workflow should be carried on in DVR. As of now, I
Main question here is: does step 5 make any sense at all? Does this mean there is an iterative process, repeating steps 2-3-4-5 over and over again? Or, put another way, will the "Analyse All shots" command induce a change in HDR10+ trims after a small correction in grading?

Guess I will try and ask on the DVR forum. If any luck, will post back here.

Sergio
Title: Re: HDR10+ workflow
Post by: vastunghia on April 08, 2022, 09:26:10 AM
DVR manual says "The Enable Tone Mapping Preview checkbox lets you turn the tone mapping trim being applied off and on, so you can evaluate how the downconverted SDR version looks on your HDR display", so I draw these (hopefully) final conclusions:
Adjusted once again first post to reflect this.

Sergio
Title: Re: HDR10+ workflow
Post by: timbytheriver on April 08, 2022, 10:02:04 AM
Hi Sergio

Very interesting re the incorrect MaxFALL values being passed by the ProRes file. I hadn't noticed this. Thanks for the fix!

Just out of interest, have you used this HDR10+ metadata test file with your 550nit panel? https://ff.de/hdr10plus-metadata-test/ I see no change on my panel running the clips. It would be useful to know your result!

Re the 'HDR Mastering is for X' and bezier curves, anchor points et al, you might also be interested in this thread on the DVR forum: https://forum.blackmagicdesign.com/viewtopic.php?f=21&t=97953&p=824715#p824715

The HDR10+ workflow is very poorly implemented and documented at present imo.  :-\

Title: Re: HDR10+ workflow
Post by: vastunghia on April 08, 2022, 11:02:07 AM
Just out of interest, have you used this HDR10+ metadata test file with your 550nit panel? https://ff.de/hdr10plus-metadata-test/ I see no change on my panel running the clips. It would be useful to know your result!

Thank you Tim, nice test, I tried it on my TV and I definitely see very different results as HDR10+ metadata change, e.g. severe clipping in highlights in the second version of the clip and so on.

Re the 'HDR Mastering is for X' and bezier curves, anchor points et al, you might also be interested in this thread on the DVR forum: https://forum.blackmagicdesign.com/viewtopic.php?f=21&t=97953&p=824715#p824715

Very useful, thank you! From this I understand that (1) from DVR there is the possibility of exporting also Profile-B json HDR10+ metadata (didn't notice!) and that (2) currently TargetedSystemDisplayMaximumLuminance seems to be hard-coded @400 nits in HDR10+ json file. This may be somehow related to DVR exporting HDR10 metadata with MaxFALL = 400 maybe? Heaven knows. Probably not.

The HDR10+ workflow is very poorly implemented and documented at present imo.  :-\

To say the least. This is an understatement actually ;).

Planning to prepare PQ10 / HDR10 / HDR10+ prof-A / HDR10+ prof-B versions of the same video to test on my TV. Will take some time, but keep you posted.

Sergio

Ps: I also had a closer look at HDR10+ json exported from DVR and noticed that in some cases TargetedSystemDisplayMaximumLuminance is set @0 nits :o Not clear what's going on here at all. Whole process looks pretty buggy, manual inspection is needed everywhere. EDIT: looks like Profile-A json files have TargetedSystemDisplayMaximumLuminance and MaxScl incorrectly set @0 nits, while Profile-B files have them respectively set @400 and 10000 nits (which is probably not optimal yet, but better than 0)! Updating post #1 to suggest exporting Profile B HDR10+ metadata.
Title: Re: HDR10+ workflow
Post by: timbytheriver on April 08, 2022, 11:57:33 AM
I tried it on my TV and I definitely see very different results as HDR10+ metadata change

Ha! Now I'm confused – and a bit jealous! ;)
Title: Re: HDR10+ workflow
Post by: vastunghia on April 08, 2022, 12:07:20 PM
Ha! Now I'm confused – and a bit jealous! ;)

Maybe you should not. I can think of 3 causes for your TV behavior:
S
Title: Re: HDR10+ workflow
Post by: timbytheriver on April 08, 2022, 01:31:57 PM
1. On paper yes – the Panasonic FZ952 luminance curve hard-lines at 900. Clips #1 & #2 highlights look identical though.
2. I think black-magic stuff certainly! This is the achilles-heel of the whole metadata thing: if it's just being overridden by the TV's black box, we might as well pack up and go home.
3. The on-screen badge changes to HDR10+ – so notionally it's seeing it correctly.

Title: Re: HDR10+ workflow
Post by: vastunghia on April 08, 2022, 03:30:06 PM
This is the achilles-heel of the whole metadata thing: if it's just being overridden by the TV's black box, we might as well pack up and go home.

Very well said. And indeed I think that is the case.

I think I read somewhere that HDR10+ suffers a lot from this (tv's doing magic on a not-so-strictly defined standard) while Dolby Vision does not, i.e. remains more consistent across different displays. But I may be wrong.

S
Title: Re: HDR10+ workflow
Post by: timbytheriver on April 12, 2022, 12:09:56 PM
7. When you are satisfied with the result, in DVR go to Deliver page, start with ProRes Master preset and then apply the following settings:

• Embed HDR10 Metadata: enabled

I've noticed that if this checkbox is enabled for the final ProRes render, the metadata may contain two sets of MaxFALL, MaxCLL data: One set is marked as MaxFALL_x_Original. I've taken to rendering the ProRes master without the Embed HDR10 metadata enabled, and just using the exported .json file as the definitive source for the metadata. This might avoid these duplicate data sets. Who knows…!

As a PS I seem to be able to throw plain HDR10 files up to 4000nits Max at my TV – and it does a great internal job of tone-mapping the overs! The same HDR10+ file with all the nice metadata in place is recognised as such – but there really doesn't appear to be a visually superior roll-off happening. This tells me that either the TV is doing a good job, or the metadata is being overridden by the TV (bad).

Obviously we need the correct valid metadata present in a production environment, but I wonder how many TVs out there in the wild are just ignoring the colourist's carefully crafted mastering, and quietly 'doing their own thing'…  :o


 
Title: Re: HDR10+ workflow
Post by: vastunghia on April 19, 2022, 09:58:02 PM
I've noticed that if this checkbox is enabled for the final ProRes render, the metadata may contain two sets of MaxFALL, MaxCLL data: One set is marked as MaxFALL_x_Original.

Yes, I noticed too, I think this is what is going on under the hood:
So in my view this should be harmless, but I can also understand the reason one could feel more comfortable in avoiding any unnecessary metadata here.

This tells me that either the TV is doing a good job, or the metadata is being overridden by the TV (bad).

I think you should be happy as long as you do not see any clipping occurring whatsoever, at least in the first place. I still do not fully understand why a TV should display clipping as a result of its incapability to reach extreme nit values. So I guess your TV manufacturer is sharing my view somehow.

I wonder how many TVs out there in the wild are just ignoring the colourist's carefully crafted mastering, and quietly 'doing their own thing'…  :o

Yup, you just have to walk into a TV store where they are typically displaying the same video on dozens of different TV models... they all look so different. I think we just have to live with it. But that's why I'm happy I'm not a professional video maker... I just want my private footage to look the way I want on my particular TV (which I use for grading). So guess I'll have to stick to my TV forever ;D

S
Title: Re: HDR10+ workflow
Post by: timbytheriver on April 21, 2022, 01:13:39 PM
I still do not fully understand why a TV should display clipping as a result of its incapability to reach extreme nit values.
I believe only grading reference monitors are designed to display the results of actual clipping – they have a hard clip in other words, so that colourists can actually see the effect of over-driven signals, and should have the technical skills to limit this to avoid damage. Modern consumer TVs are I think designed never to hard-clip, because a) Most consumers would think it was a visually 'broken'. b) Constant high-nit values would cause damage.

Tbh, I'd prefer it if I could switch my TV into a hard-clip mode, especially when trying to work with dynamic metadata in HDR flavours. I wonder whether there's a way… Maybe a custom calibration LUT?

Btw, did you ever get to actually see the effect of your HDR10+ metadata on your display?  :D

Title: Re: HDR10+ workflow
Post by: vastunghia on April 27, 2022, 01:15:21 PM
Btw, did you ever get to actually see the effect of your HDR10+ metadata on your display?  :D

I prepared 4 versions of the same clip, namely
The clip included some very bright scenes, some more balanced scenes, as well as some very dark scenes with a few bright spots.

To assess the four versions of the clip, I photographed the TV screen from a long distance in a dark room, of course taking Raw pictures and baking them with exactly the same (somewhat neutral) settings in ACR.

The results:
So yes, in the end I could find some differences with my TV -- but very subtle, in many cases visible more by comparing the sample pictures histogram rather than really perceivable with the naked eye.

Sergio
Title: Re: HDR10+ workflow
Post by: vastunghia on April 28, 2022, 12:20:13 PM
Edited post #1 to reflect further findings, namely
Title: Re: HDR10+ workflow
Post by: timbytheriver on April 28, 2022, 03:17:38 PM
Hi Sergio

Thank you for your comprehensive testing and feedback. I'm still digesting it. It certainly seems to agree broadly with my own, in that the 10+ metadata seems to be doing only very subtle things – a good thing I guess. And still we don't know if/how the TV is doing its own 'trim'. If DVR allowed us access to the trim controls we could I suppose make extreme adjustments – the easier to see the metadata at work.  Is there any change in DVR v18 I wonder?

I read on some forum the other day that a major Hollywood studio has just withdrawn from the HDR10+ alliance. Words like "Dead duck…" were being used with reference to HDR10+ future… Sadly this might all be a bit Betamax in a year's time… :(

*Edit I note with a slight *groan* that a) No talk of HDR10+ update in DVR18(beta), but b) oddly this is added: "Support for the HDR Vivid standard." This is apparently a version of the HDR10/PQ standard that the Chinese market is leaning toward. I think it sounds like one of those dodgy showroom picture styles on a TV – to be avoided! :0
Title: Re: HDR10+ workflow
Post by: vastunghia on April 28, 2022, 05:52:26 PM
I read on some forum the other day that a major Hollywood studio has just withdrawn from the HDR10+ alliance. Words like "Dead duck…" were being used with reference to HDR10+ future… Sadly this might all be a bit Betamax in a year's time… :(

Yup they've been saying that HDR10+ is dead for a long time already. And I think they are right. Personally, if I didn't own a TV which is capable of HDR10+ only (and not Dolby Vision), I would not have much interest in this technology. Even though I don't see a royalty-free contender to Dolby.

But then again, considering the very limited benefit that dynamic metadata seems to bring to my TV (at least with respect to static metadata HDR), maybe the real point is that we should not be joining the dynamic metadata hype.

At this stage this is more a style exercise to me, fueled by some curiosity in how these technologies work (not very well I must say after digging into it).

S

Ps: I had to google Betamax  ;)
Title: Re: HDR10+ workflow
Post by: timbytheriver on April 28, 2022, 07:05:02 PM
Ps: I had to google Betamax  ;)
Oops. Just showed my age… ;)