[FFmpeg-trac] #9407(ffmpeg:reopened): Broken Conversion: yuv444p10le to yuv444p

FFmpeg trac at avcodec.org
Mon Sep 6 06:01:17 EEST 2021

#9407: Broken Conversion: yuv444p10le to yuv444p
             Reporter:  Michael      |                    Owner:  (none)
  Witten                             |
                 Type:  defect       |                   Status:  reopened
             Priority:  normal       |                Component:  ffmpeg
              Version:  unspecified  |               Resolution:
             Keywords:  pix_fmt yuv  |               Blocked By:
  yuv444p10le yuv444p 10-bit format  |
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
Comment (by Balling):

 >I think a transfer function issue

 a) we do not support EOTF awared scale, see #6694
 b) ycbcr to ycbcr does not require going to linear RGB. Everything is done
 on R'G'B. (The exceptions are of course newer ICtCp, BT.2020-cl
 (everything on Blu-ray and streams uses bt.2020-'''n'''cl though)) and
 chromaticity derived constant luminance systems. Those operate on linear

 c) Please note that Imagemagick has a bug that it says it is sRGB when it
 only has gAMA chunk without sRGB chunk, it is present on all from svg
 images on wikipedia, an insane bug that destroyes colors. And also that
 0.4545445 is just 2.2 pure gamma which is not sRGB, in this case ffmpeg
 appers to set the tag and even say it is perceptual rendering intent
 inside sRGB chunk. Now, perceptual can be handled  very differently by
 different software, so... also please note that it is tagged as sRGB, but
 the correct is gAMA chunk of 1/2.4, since BT.709 transfer must be
 presented using 2.4 pure gamma on perfect display. This is also a bug in
 ffmpeg, of course. We do  ot change the transfer either.

 Now, I do not think how you think we will fix it if it were not fixed in
 the past 10 years or so...
Ticket URL: <https://trac.ffmpeg.org/ticket/9407#comment:9>
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