jpeg rgb file with subsampling decodes incorrectly

[ami_stuff]

​https://raw.githubusercontent.com/libjxl/testdata/1405a214a8232991c585dc2164b5dec5bd559a33/jxl/flower/flower.png.im_q85_rgb_subsample_blue.jpg

it has 4:4:1 (22:22:11) subsampling

./ffmpeg -i flower.png.im_q85_rgb_subsample_blue.jpg -y out.bmp
ffmpeg version N-109855-g2296078397 Copyright (c) 2000-2023 the FFmpeg developers
  built with gcc 9 (Ubuntu 9.4.0-1ubuntu1~20.04.1)
  configuration: 
  libavutil      58.  1.100 / 58.  1.100
  libavcodec     60.  2.100 / 60.  2.100
  libavformat    60.  2.100 / 60.  2.100
  libavdevice    60.  0.100 / 60.  0.100
  libavfilter     9.  1.100 /  9.  1.100
  libswscale      7.  0.100 /  7.  0.100
  libswresample   4.  9.100 /  4.  9.100
Input #0, image2, from 'flower.png.im_q85_rgb_subsample_blue.jpg':
  Duration: 00:00:00.04, start: 0.000000, bitrate: 215322 kb/s
  Stream #0:0: Video: mjpeg (Baseline), yuvj444p(pc, bt470bg/unknown/unknown), 2268x1512, 25 fps, 25 tbr, 25 tbn
Stream mapping:
  Stream #0:0 -> #0:0 (mjpeg (native) -> bmp (native))
Press [q] to stop, [?] for help
[swscaler @ 0x55bc14914d40] deprecated pixel format used, make sure you did set range correctly
    Last message repeated 3 times
Output #0, image2, to 'out.bmp':
  Metadata:
    encoder         : Lavf60.2.100
  Stream #0:0: Video: bmp, bgr24(pc, gbr/unknown/unknown, progressive), 2268x1512, q=2-31, 200 kb/s, 25 fps, 25 tbn
    Metadata:
      encoder         : Lavc60.2.100 bmp
frame=    0 fps=0.0 q=-0.0 size=       0kB time=00:00:00.00 bitrate=N/A speed=N/[image2 @ 0x55bc147d68c0] The specified filename 'out.bmp' does not contain an image sequence pattern or a pattern is invalid.
[image2 @ 0x55bc147d68c0] Use a pattern such as %03d for an image sequence or use the -update option (with -frames:v 1 if needed) to write a single image.
frame=    1 fps=0.0 q=-0.0 Lsize=N/A time=00:00:00.00 bitrate=N/A speed=   0x    
video:10047kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown

[Balling]

Yep

[Balling]

Fixed in b18a9c29713abc3a1b081de3f320ab53a47120c6.

[Balling]

Broken again in c3625ccfcd74bacff2ec6764dea8ef2beb5e9ef7.

[Balling]

​https://patchwork.ffmpeg.org/project/ffmpeg/patch/20230419181126.38662-3-leo.izen@gmail.com/

Will fix it.

[Leo Izen]

Fixed by 869248c053856e654002f0650b02d22648b563ba.