[FFmpeg-trac] #7037(avcodec:open): ffmpeg destroys HDR information when encoding

FFmpeg trac at avcodec.org
Thu Dec 19 00:41:16 EET 2019

#7037: ffmpeg destroys HDR information when encoding
             Reporter:  mario66      |                    Owner:  cehoyos
                 Type:  enhancement  |                   Status:  open
             Priority:  normal       |                Component:  avcodec
              Version:  git-master   |               Resolution:
             Keywords:  libx265 hdr  |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |

Comment (by mario66):

 Yes, I know, it is a "bad link". But I do not have any more scripts, I
 didn't find any script that works. I think there is currently none. (If
 there was one no need for this bug report)
 Then there is this link: https://forum.doom9.org/showthread.php?t=175227
 where people just tinkered around a set of parameters so that they got the
 meta data transferred for a particular video. (Which needs to be changed
 for every video individually)
 But to be honest I did not thinker around with any scripts or parameters,
 I started this bug report where I hoped people would understand the issue
 and submit a fix.
 Because in the end I would not be able to tell if everything went
 successfully or if there was a "twist" which I was not aware of. But you,
 I hoped, are the experts. You could tell whether an output is complete or
 incomplete, and you can tell what exactly one needs to do to avoid loss of
 HDR information. I think it is better if there is something official, a
 documentation or functionality, coming from the developers itself. This
 will be of great value for all of your users!

 I outlined above what would be the ideal outcome of a fix:
 1) In the end what should be possible is that the transcoded video behaves
 exactly the same in terms of HDR. My TV should use the same parameters for
 processing the video, i.e. all the meta data should be indistinguishable.
 I should not be able to tell a difference between the original and the
 transcoded version except if you have very good vision and can see the
 compression artifacts (which I cannot for example).
 2) A clear documentation of what works and what does not work and what you
 have to be aware of

 You keep telling that "nvidia NVAPI already support (in windows only)
 dolby vision signalling". But this is irrelevant since I use x265 codec
 inside ffmpeg. Also x265 supports HDR10 but then when combined with ffmpeg
 all the meta data are lost. This is an ffmpeg issue, not a codec issue.

 Thanks four your tenacity, I hope I could clarify a bit more. :-)

Ticket URL: <https://trac.ffmpeg.org/ticket/7037#comment:52>
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