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

FFmpeg trac at avcodec.org
Sun Jan 19 13:21:50 EET 2020

#7037: ffmpeg destroys HDR metadata 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):

 I appreciate that you start to care about the average end user who is not
 so familiar with color spaces. Indeed, as Balling suggested, even for SDR
 videos tags like "colour_primaries=BT.709" are present, and they are lost
 after transcode!
 Now I'm not sure if this is even a problem because TVs could assume this
 as the default color space, but still it is a scary thought that all my
 transcoded videos are destroyed by missing color information. For example
 what happens if I buy a new TV that does not assume BT.709 as the default?
 Will I be even able to watch the videos without huge shift in color space?

 I think this topic has too long been ignored. Color management experts
 like you always knew how to tweak those options, but 99,9% of end users
 did not. I did not find any reference to this missing meta data problem in
 any guides on how to transcode a Blu Ray video. I think this is not known
 to the general public. I'm always eager to learn new things but there are
 always things even I do not know that I do not know them. The "unknown
 unknowns". There is no chance to learn them if no one writes about this.

 There is a lot of room for improvements in documentation, and I would be
 very happy if this would also be a result of our interesting discussion. I
 tried to trigger something with this ticket:
 https://trac.ffmpeg.org/ticket/8482 but was closed by my fried "cehoyos"
 who has no interest in improving this project.

Ticket URL: <https://trac.ffmpeg.org/ticket/7037#comment:70>
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