Color on the Web CG meeting

TPAC, 07 Nov 2017


(see below)
Chris Lilley



mark watson, netflix


nigel meggit, bbc

simon fraser, apple

paul kerr, netflix

pierre lemieux, movielabs

chris lilley, w3c

frederick hubenette, google

chris cameron, google

bill hofman, dolby

Agenda suggestions

heif and jpeg xr handle hdr and wcg

canvas linear pixel math

tone mapping, hdr mapped to smaller space

rendering intent

using canvas rather than css to get finer control (!)

Actual meaning of black, white

"brightest graphics white" not 10,000nit flare


<smfr> https://www.w3.org/TR/ttml2/#hdr-compositing

raise issue on ttml2 compositing a) 2.4 gamma not real EOTF b) 80 nits not desirable value, too low

Can we fix IEC 61966-2-1:1999 for 80nits?

tv grading uses 100nits in dark room. so brighter in a mid lit room

Displaying HDR

how to get a good signal, then how to display that signal

secret sauce for the second part from tv manufacturers

tvs in hdr mode with a shader to boost up sdr content

<hubbe> https://docs.google.com/document/d/1A__vvTDKXt4qcuCcSN-vLzcQKuchnYmu8TFMDseIZJE/edit?usp=sharing

scrgb with 100 nits = 1.0

viewing environment modification not a linear shift - black area lift as well

css as the metadata

separate authorial from end-user decisions

three problems - compositing, viewing environment compensation, and tone mapping to display capabilities

compositing needs to know the level at which a paper white was graded. may be 100 for broadcast or may be like 300 for youtube hdr content

variable luminance gain like in ttml2

needs knowledge of the HDR is is compositing onto

uhd bluray grappling with the sdr hdr compositing for UI elements, now

HLG has a recommended way to composite SDR; 2020 and 2100 with PQ do not

<nigel> https://github.com/w3c/ttml2/issues/233#issuecomment-296168903

<nigel> https://github.com/w3c/ttml2/issues/397#issuecomment-313369591

<nigel> ACTION: nigel Find out where the assertion that sRGB peak white (narrow range) maps to 75% HLG originates

canvas beyond sRGB

half-float w 2 color spaces, extended sRGB like cg colorspace, and half float scrgb (linear)

first is what chrome composites hdr in today

working colorspace prevents extended RGB canvas being clipped to sRGB

displaycolorspace (P3) on mac, scrgb on ios




Summary of Action Items

[NEW] ACTION: nigel Find out where the assertion that sRGB peak white (narrow range) maps to 75% HLG originates

Summary of Resolutions

[End of minutes]