[FFmpeg-trac] #11342(ffmpeg:new): colorspace filter does not apply dither=fsb when in/out primaries is the same

[FFmpeg]

#11342: colorspace filter does not apply dither=fsb when in/out primaries is the
same
-------------------------------------+-------------------------------------
             Reporter:  Seb          |                     Type:  defect
               Status:  new          |                 Priority:  minor
            Component:  ffmpeg       |                  Version:  git-
             Keywords:  colorspace   |  master
  dither dithering                   |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 I have 10bits BT.709 videos and i want to use colorspace filter to convert
 to 8bits (personal choice over format filter).
 The problem is that dither=fsb options does not work when output primaries
 is the same as input.

 This example does not apply any dithering :
 {{{
 % ffmpeg -i input -vf colorspace=all=bt709:format=yuv420p:dither=fsb [...]
 }}}
 But dither=fsb works with this workaround, by forcing a primaries
 transformation (i used bt2020 but it could be anything).
 {{{
 % ffmpeg -i input -vf
 zscale=p=2020,colorspace=all=bt709:format=yuv420p:dither=fsb [...]
 }}}

 Note:Dither is also disabled with fast=1

 For now i can use my workaround, but this slows down the encoding by a lot
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/11342>
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