[FFmpeg-trac] #9085(avcodec:reopened): JPEG: YCCK too green
FFmpeg
trac at avcodec.org
Wed Mar 24 00:18:00 EET 2021
#9085: JPEG: YCCK too green
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Reporter: Balling | Owner:
Type: defect | Status: reopened
Priority: normal | Component: avcodec
Version: git-master | Resolution:
Keywords: mjpeg cmyk | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
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Comment (by Balling):
Okay my latest idea is that it is subsampling issue, subsampled CMYK and
YCCK (yeah, CMYK is also insanely affected, at least that uses in Ci
endcoding, see #4772) are good and not subsampled are bad. That is
regression of d56c373391d334d3dc29c752955fd17f0cef7ff9.
Franky speaking I am starting to fear that this is just a problem of not
limiting CMYK green values... CMYK is not a triange or prism (in XYZ) and
so we get that problem. Green should be limited to much lower values.
I also found good test here: https://github.com/mozilla/mozjpeg/issues/23
Also, we will try to fix this in Chromium, and if it will work with our
native jpeg decoder, we will try to get to fallback (that is ffmpeg).
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Ticket URL: <https://trac.ffmpeg.org/ticket/9085#comment:23>
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