Re: [EXTERNAL] Re: ISO 22028-5 Support (adding dWLm (Diffuse White Luminance Metadata)

The ISO spec states it this way:

If the luminance of the diffuse white differs from the default reference display nominal diffuse white

Luminance defined in 4.5.5 (203nits), it should be indicated using dWLm (Diffuse White Luminance Metadata) metadata.

There could be a desire by creatives to vary diffuse white from “reference white condition” (± some latitude). This is where the metadata is useful. There are also SDR examples where for “single-master HDR/SDR workflows” groups map to SDR with the expectation that the viewing peak luminance is at/above 203nits (not 100nits).

MovieLabs SDR to HDR conversion recommendation uses MDCV to describe SDR’s diffuse white luminance level but they could instead dWLm to describe the content itself.

Chris

From: Pierre-Anthony Lemieux <pal@sandflow.com>
Date: Sunday, December 10, 2023 at 4:57 PM
To: Seeger, Chris (NBCUniversal) <Chris.Seeger@nbcuni.com>
Cc: Leonard Rosenthol <lrosenth@adobe.com>, Chris Blume (ProgramMax) <programmax@gmail.com>, Leo Barnes <lbarnes@apple.com>, public-png@w3.org <public-png@w3.org>
Subject: Re: [EXTERNAL] Re: ISO 22028-5 Support (adding dWLm (Diffuse White Luminance Metadata)
Ok, so, when Rec. 2100 color spaces are signaled, dWLm should indicate 203 nits?

On Sun, Dec 10, 2023 at 1:35 PM Seeger, Chris (NBCUniversal)
<Chris.Seeger@nbcuni.com> wrote:
>
> From BT.2408:
>
>
>
> “The reference level, HDR Reference White, is defined in this Report as the nominal signal level
>
> obtained from an HDR camera and a 100% reflectance white card resulting in a nominal luminance
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> of 203 cd/m2 on a PQ display or on an HLG display that has a nominal peak luminance capability of
>
> 1 000 cd/m2. That is the signal level that would result from a 100% Lambertian reflector placed at the
>
> centre of interest within a scene under controlled lighting, commonly referred to as diffuse white.”
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>
>
> And
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>
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> “A2.6 Conclusions
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> The HDR Reference White level of 203 cd/m2 in Table 1 of this Report is consistent with the mean
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> diffuse white as measured in the content analyzed in this Annex.”
>
>
>
> It is my understanding that in the case of HDR at a reference peak white level, reference white and diffuse white have the same luminance level in nits of 203 cd/m2 in BT.2408 under the conditions described above.
>
>
>
> China has suggested they would like to use a higher ref/diffuse white luminance and Cinema desires (in my discussions) that diffuse white is variable by scene.
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>
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> So, in my opinion it is valuable to have metadata that describes the variability of diff/ref white in still photography or video to assist in optimized tone mapping.
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>
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> For SDR our TV Luminance survey suggests that for consumer TV viewers, the SDR peak white value is approximately the same as HDR reference white or 203nits (100nits is left over from CRT’s and is a technical reference level only; not reflecting the real world).
>
>
>
> -Chris
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>
>
>
>
> From: Pierre-Anthony Lemieux <pal@sandflow.com>
> Date: Sunday, December 10, 2023 at 1:40 PM
> To: Seeger, Chris (NBCUniversal) <Chris.Seeger@nbcuni.com>
> Cc: Leonard Rosenthol <lrosenth@adobe.com>, Chris Blume (ProgramMax) <programmax@gmail.com>, Leo Barnes <lbarnes@apple.com>, public-png@w3.org <public-png@w3.org>
> Subject: [EXTERNAL] Re: ISO 22028-5 Support (adding dWLm (Diffuse White Luminance Metadata)
>
> What is the relationship between _diffuse white luminance metadata_
> and _reference white_ specified in [Report ITU-R
> BT.2408](https://urldefense.com/v3/__https://www.itu.int/pub/R-REP-BT.2408<https://urldefense.com/v3/__https:/www.itu.int/pub/R-REP-BT.2408>)?__;!!PIZeeW5wscynRQ!ub763y3GiKz8Vc_InDmIAdz1KhEW63ph3Kc-5caFlEQ2w5agLgaIVK-KIv88_bIwMOMBzc-MO81sNw$
>
> On Sun, Dec 10, 2023 at 9:48 AM Seeger, Chris (NBCUniversal)
> <Chris.Seeger@nbcuni.com> wrote:
> >
> > Thanks Leonard.
> >
> > Get Outlook for iOS
> > ________________________________
> > From: Leonard Rosenthol <lrosenth@adobe.com>
> > Sent: Sunday, December 10, 2023 12:33:02 PM
> > To: Seeger, Chris (NBCUniversal) <Chris.Seeger@nbcuni.com>; Chris Blume (ProgramMax) <programmax@gmail.com>; Leo Barnes <lbarnes@apple.com>
> > Cc: public-png@w3.org <public-png@w3.org>
> > Subject: [EXTERNAL] Re: ISO 22028-5 Support (adding dWLm (Diffuse White Luminance Metadata)
> >
> >
> > To clarify, I am NOT suggesting we hold 3rd edition for this!   I think we should publish 3rd edition as is – with no additions.  My understanding is that we make any technical changes at this point, we have to go back to IPR reviews, etc. – it’s just not a matter of “sneaking it in”, and to your point – we want this out sooner rather than later.
> >
> >
> >
> > If changes come out of the Feb meeting, including what you propose below, we can address those in a future update.
> >
> >
> >
> > The work isn’t just around ICC profiles as we understand their use today – but also the possibilities of what other types of data/info they can/should contain (specifically around HDR) and how that would interact with native format functionality.  For example, if TC 42 & ICC decide that the “diffuse white tag” should be inside an ICC profile instead of a format-centric chunk – then we would need to update our spec to address that case, and what would happen if they both existed, etc.
> >
> >
> >
> > Stripping of public chunks is not recommended – and we should be sure to make sure we make that clear in our Marketing/Comms.   (NOTE: ignoring them in a decoder, which is permitted, is not the same thing)
> >
> >
> >
> > Leonard
> >
> >
> >
> > From: Seeger, Chris (NBCUniversal) <Chris.Seeger@nbcuni.com>
> > Date: Sunday, December 10, 2023 at 12:15 PM
> > To: Leonard Rosenthol <lrosenth@adobe.com>, Chris Blume (ProgramMax) <programmax@gmail.com>, Leo Barnes <lbarnes@apple.com>
> > Cc: public-png@w3.org <public-png@w3.org>
> > Subject: Re: ISO 22028-5 Support (adding dWLm (Diffuse White Luminance Metadata)
> >
> > EXTERNAL: Use caution when clicking on links or opening attachments.
> >
> >
> >
> > Hi Leonard,
> >
> >
> >
> > Can we agree that we don’t want this to hold 3rd edition any longer than a month? The CICP chunk is more important than anything because it’s holding up content creators making native HDR graphics for production.
> >
> >
> >
> > The diffuse white tag is a simple addition and I think most important addition. I’ve done the work in a branch that is submitted and I’m hopeful it will be easy to review.  The diffuse white tag ties into work to change the floating point normalization in other standards.
> >
> >
> >
> > ICC profiles are in my eyes a useful method, but not as important as a real PNG chunk since it will be harder to strip (once supported), so I’d hope we don’t hold up work in W3C.
> >
> >
> >
> > Leonard, I’m happy to be a proponent for secondary work in ICC once 3rd edition is done.
> >
> >
> >
> > Best,
> >
> >
> >
> > Chris Seeger
> >
> > Director, Advanced Content Production
> >
> > Office of the CTO
> >
> > C: 551-238-3768
> >
> >
> >
> >
> >
> > From: Leonard Rosenthol <lrosenth@adobe.com>
> > Date: Sunday, December 10, 2023 at 11:59 AM
> > To: Seeger, Chris (NBCUniversal) <Chris.Seeger@nbcuni.com>, Chris Blume (ProgramMax) <programmax@gmail.com>, Leo Barnes <lbarnes@apple.com>
> > Cc: public-png@w3.org <public-png@w3.org>
> > Subject: [EXTERNAL] Re: ISO 22028-5 Support (adding dWLm (Diffuse White Luminance Metadata)
> >
> > Yes, I (and hopefully Chris L. as well) am meeting with that group and ICC in Tokyo in February to coordinate future work on HDR and still images. Given that we have a number of issues on the table for that meeting – which can/will impact PNG – I would recommend that we don’t rush anything.
> >
> >
> >
> > Leonard
> >
> >
> >
> > From: Seeger, Chris (NBCUniversal) <Chris.Seeger@nbcuni.com>
> > Date: Sunday, December 10, 2023 at 9:31 AM
> > To: Chris Blume (ProgramMax) <programmax@gmail.com>, Leo Barnes <lbarnes@apple.com>
> > Cc: public-png@w3.org <public-png@w3.org>
> > Subject: ISO 22028-5 Support (adding dWLm (Diffuse White Luminance Metadata)
> >
> > EXTERNAL: Use caution when clicking on links or opening attachments.
> >
> >
> >
> > Hi All,
> >
> >
> >
> > Is it too late to add one more chunk to 3rd Edition that is inline with our MDCV efforts?
> >
> >
> >
> > I was recently made aware of ISO 22028-5 which defines High dynamic range and wide colour gamut encoding for still images (HDR/WCG). It adds an additional metadata: Diffuse White Luminance Metadata. It’s a great companion to the new chunks we’ve added in PNG.  The ISO effort has defined one more important element that I’ve been proposing for SMPTE ST 2086 (and am close to bringing to SMPTE).
> >
> >
> >
> > Diffuse White Luminance Metadata allows for improved tone-mapping because it establishes a point above which compression of highlights might begin.
> >
> >
> >
> > It’s a simple two-byte additional chunk which I’ve authored to a branch if anyone wants to take a look (Issue #390).  I need a chunk value to insert to finish up.
> >
> >
> >
> > Best,
> >
> > Chris