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[ttml2] Signaling HDR pixels in PNG for use with <image>

From: Pierre-Anthony Lemieux via GitHub <sysbot+gh@w3.org>
Date: Wed, 15 Feb 2017 21:30:59 +0000
To: public-tt@w3.org
Message-ID: <issues.opened-207933961-1487194258-sysbot+gh@w3.org>
palemieux has just created a new issue for 
https://github.com/w3c/ttml2:

== Signaling HDR pixels in PNG for use with <image> ==
The TTML2  allow PNG images to be displayed. In order to allow the use
 of the `image` with HDR video (see #233 for additional background on 
HDR video), TTML2 should support PNG sources carrying HDR images as 
specified in the 
[attached](https://github.com/w3c/ttml2/files/778427/png_st2084_20170125.zip).
 The latter is intended to be compatible with current PNG 
implementations and uses existing PNG structures:

- HDR pixels are carried PQ-encoded using full-range quantization
- the profile name field of the iCCP chunk is used to signal the color
 system
- implementations that do not recognize the magic profile names but
support the iCCP chunk will process the image using an embedded ICC
profile, which can evolve as the ICC standard evolves
- implementations that do not recognize the iCCP chunk should display
the image according to the cHRM and gAMA chunks
- implementations that ignore iCCP, cHRM and gAMA chunks will still
display the image
- implementations that merely blit the PNG onto video with the same
HDR colorspace, but without any color conversion, would end-up with an
adequate image
 

Please view or discuss this issue at 
https://github.com/w3c/ttml2/issues/244 using your GitHub account
Received on Wednesday, 15 February 2017 21:31:05 UTC

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