Hi All,
Hi All,
Could you elaborate on why cICP is not independent of mDCV and cLLI? Most video has existed without both mDCV and cLLI for many years. What would the adverse effects of their absence be?
Any method that accelerates the implementation of cICP in libpng without causing any other conflicts is essential. We have long lacked the ability to identify video formats in PNG still image formats which has caused mismapping for years (sRGB vs BT.709). With cICP, we will avoid further issues now that HDR and WCG are in common use.
John:
* Can you explain what you mean by “PQ with sRGB data”?
* Also, can you point me to H.273 that indicates 1.0 corresponds to 2,000 cd/m2? PQ peak white = 10,000 cd/m2 and 1.0 PQ in floating point is currently 1 cd/m2 (but will become diffuse white in cd/m2 if all goes well).
Best,
Chris Seeger
Director, Advanced Content Production
Office of the CTO
C: 551-238-3768
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Chris
From: Chris Lilley <chris@w3.org>
Date: Friday, January 3, 2025 at 8:12 PM
To: jbowler@acm.org <jbowler@acm.org>, Seeger, Chris (NBCUniversal) <Chris.Seeger@nbcuni.com>
Cc: Chris Blume (ProgramMax) <programmax@gmail.com>, Portable Network Graphics (PNG) Working Group <public-png@w3.org>
Subject: Re: [EXTERNAL] Re: [PNG] Meeting topics - Jan 6, 2025
I agree with John that delaying cLLI and mDCV would be unfortunate and
produce breakage.
On 2025-01-03 15:59, John Bowler wrote:
> It's trivial for me to implement those chunks and both are pretty much
> essential for producing correct test files, cLLI for PQ encoding with
> sRGB data (which would come out very dark without cLLI since the PQ
> 1.0 corresponds to 2000cd/m2; this is assuming I understand H273).
> mDCV when data with a different white point is encoded in a colour
> space, particular colour space 10 (SMPTE ST 428-1). Without those
> chunks the display will be confusing in a conformant decoder; bad for
> testing.
--
Chris Lilley
@svgeesus
Technical Director @ W3C
W3C Strategy Team, Core Web Design
W3C Architecture & Technology Team, Core Web & Media
