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

FFmpeg trac at avcodec.org
Mon Dec 16 14:51:17 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 Balling):

 Replying to [comment:34 mario66]:
 You are 100 percent wrong. 10 bit color has nothing to do with HDR. It is
 just used because 1) it was done to accelerate technology (and it worked:
 Nvidia had to activate 10 bit color in Photoshop on geforce line (actually
 what they did is they activated 10 bit in WINDOWED OpenGL API))
 2) perceptual quantizer is HDR and HDR IS PQ. Unfortunately, 8 bit was
 really not enough for it. That is all. Also banding issues as the HDR data
 should be modified according to display capabilities (so if mastering data
 and display data is not the same you will have convertion). And 8 bit is
 possible, for example dolby vision is just 8 bit on the wire (with
 metadata to 12 or 10 bits) (but 10 bit in files with metadata to 12 bits).

 So. HDR is only about new tone curve, the PQ. Ehat is so cool about PQ?
 Well, in gamma tone curve (the sRGB standard) stands that when light
 intensity reaches less than 0.1 nit or greater than 100 nit, there is no
 more differentiation in the color value.
 While PQ (ST.2084) provides detail in both the 100 to 10000 nit, and the
 0.001 to 0.1 nit ranges.
 See https://docs.microsoft.com/en-us/windows/win32/direct3ddxgi/high-

 So blacks are more black (not the black itself, it is the same) and whites
 are whiter (not the white itself again).

Ticket URL: <https://trac.ffmpeg.org/ticket/7037#comment:36>
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