[FFmpeg-trac] #8971(ffmpeg:new): Contrast Adaptive Sharpening (CAS) is broken

[FFmpeg]

#8971: Contrast Adaptive Sharpening (CAS) is broken
-------------------------------------+-------------------------------------
             Reporter:  lextra2      |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:  ffmpeg       |                  Version:
             Keywords:  CAS          |  unspecified
  Contrast Adaptive Sharpening       |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 The [https://ffmpeg.org/ffmpeg-filters.html#cas Contrast Adaptive
 Sharpening filter] is broken. It causes chroma artefacts.

 I used the following command:
 {{{
 ffmpeg.exe -i input.png -vf cas=1 outputFFMPEG.png
 }}}

 The build version was this:
 {{{
 ffmpeg version 4.3.1-2020-11-08-full_build-www.gyan.dev Copyright (c)
 2000-2020 the FFmpeg developers
   built with gcc 10.2.0 (Rev3, Built by MSYS2 project)
   configuration: --enable-gpl --enable-version3 --enable-static --disable-
 w32threads --disable-autodetect --enable-fontconfig --enable-iconv
 --enable-gnutls --enable-libxml2 --enable-gmp --enable-lzma --enable-
 libsnappy --enable-zlib --enable-libsrt --enable-libssh --enable-libzmq
 --enable-avisynth --enable-libbluray --enable-libcaca --enable-sdl2
 --enable-libdav1d --enable-libzvbi --enable-librav1e --enable-libwebp
 --enable-libx264 --enable-libx265 --enable-libxvid --enable-libaom
 --enable-libopenjpeg --enable-libvpx --enable-libass --enable-frei0r
 --enable-libfreetype --enable-libfribidi --enable-libvidstab --enable-
 libvmaf --enable-libzimg --enable-amf --enable-cuda-llvm --enable-cuvid
 --enable-ffnvcodec --enable-nvdec --enable-nvenc --enable-d3d11va
 --enable-dxva2 --enable-libmfx --enable-libcdio --enable-libgme --enable-
 libmodplug --enable-libopenmpt --enable-libopencore-amrwb --enable-
 libmp3lame --enable-libshine --enable-libtheora --enable-libtwolame
 --enable-libvo-amrwbenc --enable-libilbc --enable-libgsm --enable-
 libopencore-amrnb --enable-libopus --enable-libspeex --enable-libvorbis
 --enable-ladspa --enable-libbs2b --enable-libflite --enable-libmysofa
 --enable-librubberband --enable-libsoxr --enable-chromaprint
   libavutil      56. 51.100 / 56. 51.100
   libavcodec     58. 91.100 / 58. 91.100
   libavformat    58. 45.100 / 58. 45.100
   libavdevice    58. 10.100 / 58. 10.100
   libavfilter     7. 85.100 /  7. 85.100
   libswscale      5.  7.100 /  5.  7.100
   libswresample   3.  7.100 /  3.  7.100
   libpostproc    55.  7.100 / 55.  7.100
 }}}

 When used on [https://i.postimg.cc/KZNqRd7B/input.png this image]
 I get [https://i.postimg.cc/WjD8vDyM/output-FFMPEG.png this output]

 Meanwhile, when using the following command with [https://github.com
 /GPUOpen-Effects/FidelityFX-
 CAS/blob/master/CasCmdLine/x64/Release/CasCmdLine.exe CasCmdLine.exe]
 {{{
 CasCmdLine.exe -Sharpness 1 -FP16 input.png outputCAS.png
 }}}
 I get [https://i.postimg.cc/Wp2sMRxV/output-CAS.png the correct output].

 Please note, the artifacts (with FFMPEG) are even worse when used on a
 video file, instead of an image.

--
Ticket URL: <https://trac.ffmpeg.org/ticket/8971>
FFmpeg <https://ffmpeg.org>
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