[FFmpeg-trac] #8455(avcodec:new): libaom-av1 damages brightness range by switching yuvj420p to yuv420p

[FFmpeg]

#8455: libaom-av1 damages brightness range by switching yuvj420p to yuv420p
-------------------------------------+-----------------------------------
             Reporter:  john123      |                    Owner:
                 Type:  enhancement  |                   Status:  new
             Priority:  wish         |                Component:  avcodec
              Version:  git-master   |               Resolution:
             Keywords:  libaom       |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-----------------------------------

Comment (by pdr0):

 Official aomenc does not support full range flag (yet)

 It's not really a "bug" per se; it's just the default ffmpeg behaviour .
 It clamps  for full range YUV flagged as full range. ie.  yuvj420p =>
 yuv420p (Y 0-255 => 16-235, CbCr 0-255 => 16-240 for 8bit) . The clamping
 is what you are seeing for the changes in levels

 Some workarounds to bypass ffmpeg behaviour (clamping full range yuvj420p
 to yuv420p) would be to either strip the full range flag (using bitstream
 filters, or 3rd party tools), or -vf
 scale=in_range=pc:out_range=pc,format=yuv420p or similar using -vf zscale

 But this means output will be full range YUV, but NOT flagged as full
 range. This can be pose problems, depending on what the target is for
 playback . Ideally, AV1 should get full range flags, like AVC, HEVC,
 eventually.

--
Ticket URL: <https://trac.ffmpeg.org/ticket/8455#comment:8>
FFmpeg <https://ffmpeg.org>
FFmpeg issue tracker