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

If it is variable by scene, could there be multiple dWLm chunks in an
animated PNG?

On Sun, Dec 10, 2023 at 4:57 PM Pierre-Anthony Lemieux <pal@sandflow.com>
wrote:

> 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
> >
> > 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.”
> >
> >
> >
> > And
> >
> >
> >
> > “A2.6 Conclusions
> >
> > The HDR Reference White level of 203 cd/m2 in Table 1 of this Report is
> consistent with the mean
> >
> > 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.
> >
> >
> >
> > 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.
> >
> >
> >
> > 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
> >
> >
> >
> >
> >
> > 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)?__;!!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
>