[FFmpeg-trac] #10000(undetermined:reopened): PNG produced from BT.709 video should be tagged as gAMA 2.4

[FFmpeg]

#10000: PNG produced from BT.709 video should be tagged as gAMA 2.4
-------------------------------------+-------------------------------------
             Reporter:  Balling      |                    Owner:  (none)
                 Type:  defect       |                   Status:  reopened
             Priority:  normal       |                Component:
                                     |  undetermined
              Version:  git-master   |               Resolution:
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
Changes (by Balling):

 * status:  closed => reopened
 * resolution:  needs_more_info =>

Comment:

 Even after f7bab37c8e66f3c77a5fbb5b5b72c10b0fb4ca5a it still writes Gamma
 1.961, that is incorrect. It must be 2.4 gamma. At least it writes PNG
 cICP now, so mpv should work correctly now, YES!! But AFAIK, fallback for
 BT.709 must be 2.4 gamma, but I cannot see that in the spec here
 https://w3c.github.io/PNG-spec/#example-4

 Command line

 ffmpeg -i C:\Users\ZAQU\Downloads\example.h264 -v:frames 1 mcasa.png

 ffmpeg.exe -v verbose -i C:\Users\ZAQU\Downloads\example.h264 -v:frames 1
 mcasa.png
 ffmpeg version N-109662-g2c3107c3e9-20230125 Copyright (c) 2000-2023 the
 FFmpeg developers
   built with gcc 12.2.0 (crosstool-NG 1.25.0.90_cf9beb1)
   configuration: --prefix=/ffbuild/prefix --pkg-config-flags=--static
 --pkg-config=pkg-config --cross-prefix=x86_64-w64-mingw32- --arch=x86_64
 --target-os=mingw32 --enable-gpl --enable-version3 --disable-debug
 --enable-shared --disable-static --disable-w32threads --enable-pthreads
 --enable-iconv --enable-libxml2 --enable-zlib --enable-libfreetype
 --enable-libfribidi --enable-gmp --enable-lzma --enable-fontconfig
 --enable-libvorbis --enable-opencl --disable-libpulse --enable-libvmaf
 --disable-libxcb --disable-xlib --enable-amf --enable-libaom --enable-
 libaribb24 --enable-avisynth --enable-chromaprint --enable-libdav1d
 --enable-libdavs2 --disable-libfdk-aac --enable-ffnvcodec --enable-cuda-
 llvm --enable-frei0r --enable-libgme --enable-libkvazaar --enable-libass
 --enable-libbluray --enable-libjxl --enable-libmp3lame --enable-libopus
 --enable-librist --enable-libssh --enable-libtheora --enable-libvpx
 --enable-libwebp --enable-lv2 --disable-libmfx --enable-libvpl --enable-
 openal --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-
 libopenh264 --enable-libopenjpeg --enable-libopenmpt --enable-librav1e
 --enable-librubberband --enable-schannel --enable-sdl2 --enable-libsoxr
 --enable-libsrt --enable-libsvtav1 --enable-libtwolame --enable-libuavs3d
 --disable-libdrm --disable-vaapi --enable-libvidstab --enable-vulkan
 --enable-libshaderc --enable-libplacebo --enable-libx264 --enable-libx265
 --enable-libxavs2 --enable-libxvid --enable-libzimg --enable-libzvbi
 --extra-cflags=-DLIBTWOLAME_STATIC --extra-cxxflags= --extra-
 ldflags=-pthread --extra-ldexeflags= --extra-libs=-lgomp --extra-
 version=20230125
   libavutil      57. 44.100 / 57. 44.100
   libavcodec     59. 57.100 / 59. 57.100
   libavformat    59. 36.100 / 59. 36.100
   libavdevice    59.  8.101 / 59.  8.101
   libavfilter     8. 54.100 /  8. 54.100
   libswscale      6.  8.112 /  6.  8.112
   libswresample   4.  9.100 /  4.  9.100
   libpostproc    56.  7.100 / 56.  7.100


 PS C:\Users\XXXX> exiftool.exe  mcasa.png
 ExifTool Version Number         : 12.44
 File Name                       : mcasa.png
 Directory                       : C:/Users/XXXX
 File Size                       : 87 kB
 File Modification Date/Time     : 2023:01:26 12:59:24+03:00
 File Access Date/Time           : 2023:01:26 12:59:42+03:00
 File Creation Date/Time         : 2023:01:26 12:59:24+03:00
 File Permissions                : -rw-rw-rw-
 File Type                       : PNG
 File Type Extension             : png
 MIME Type                       : image/png
 Image Width                     : 1280
 Image Height                    : 720
 Bit Depth                       : 8
 Color Type                      : RGB
 Compression                     : Deflate/Inflate
 Filter                          : Adaptive
 Interlace                       : Noninterlaced
 Pixels Per Unit X               : 1
 Pixels Per Unit Y               : 1
 Pixel Units                     : Unknown
 White Point X                   : 0.3127
 White Point Y                   : 0.329
 Red X                           : 0.64
 Red Y                           : 0.33
 Green X                         : 0.3
 Green Y                         : 0.6
 Blue X                          : 0.15
 Blue Y                          : 0.06
 Gamma                           : '''1.961'''
 Image Size                      : 1280x720
 Megapixels                      : 0.922


 Sample is here: https://github.com/wang-bin/QtAV/files/1132086/example.zip
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/10000#comment:5>
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