vc2 enc: gray output

[ami_stuff]

the same problem happens with 5000x5000 resolution

./ffmpeg -i test2.jpg -y -vcodec vc2 out.mkv
ffmpeg version N-112164-gcb26b85953 Copyright (c) 2000-2023 the FFmpeg developers
  built with gcc 11 (Ubuntu 11.4.0-1ubuntu1~22.04)
  configuration: 
  libavutil      58. 25.100 / 58. 25.100
  libavcodec     60. 27.100 / 60. 27.100
  libavformat    60. 13.100 / 60. 13.100
  libavdevice    60.  2.101 / 60.  2.101
  libavfilter     9. 11.100 /  9. 11.100
  libswscale      7.  3.100 /  7.  3.100
  libswresample   4. 11.100 /  4. 11.100
Input #0, image2, from 'test2.jpg':
  Duration: 00:00:00.04, start: 0.000000, bitrate: 108862 kb/s
  Stream #0:0: Video: mjpeg (Baseline), yuvj420p(pc, bt470bg/unknown/unknown), 7680x4320 [SAR 1:1 DAR 16:9], 25 fps, 25 tbr, 25 tbn
Stream mapping:
  Stream #0:0 -> #0:0 (mjpeg (native) -> dirac (vc2))
Press [q] to stop, [?] for help
[swscaler @ 0x557b04c34500] deprecated pixel format used, make sure you did set range correctly
    Last message repeated 3 times
[vc2 @ 0x557b04bd35c0] Format does not strictly comply with VC2 specs
Output #0, matroska, to 'out.mkv':
  Metadata:
    encoder         : Lavf60.13.100
  Stream #0:0: Video: dirac (drac / 0x63617264), yuv420p(tv, bt470bg/unknown/unknown, progressive), 7680x4320 [SAR 1:1 DAR 16:9], q=2-31, 600000 kb/s, 25 fps, 1k tbn
    Metadata:
      encoder         : Lavc60.27.100 vc2
frame=    0 fps=0.0 q=-0.0 size=       0kB time=00:00:00.00 bitrate=N/A speed=N/frame=    1 fps=0.3 q=-0.0 size=       1kB time=00:00:00.00 bitrate=N/A speed=  [out#0/matroska @ 0x557b04bd0640] video:6834kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.008087%
frame=    1 fps=0.2 q=-0.0 Lsize=    6835kB time=00:00:00.00 bitrate=N/A speed=   0x    
[vc2 @ 0x557b04bd35c0] Qavg: 114

./ffmpeg -i out.mkv -y out.jpg
ffmpeg version N-112164-gcb26b85953 Copyright (c) 2000-2023 the FFmpeg developers
  built with gcc 11 (Ubuntu 11.4.0-1ubuntu1~22.04)
  configuration: 
  libavutil      58. 25.100 / 58. 25.100
  libavcodec     60. 27.100 / 60. 27.100
  libavformat    60. 13.100 / 60. 13.100
  libavdevice    60.  2.101 / 60.  2.101
  libavfilter     9. 11.100 /  9. 11.100
  libswscale      7.  3.100 /  7.  3.100
  libswresample   4. 11.100 /  4. 11.100
Input #0, matroska,webm, from 'out.mkv':
  Metadata:
    ENCODER         : Lavf60.13.100
  Duration: 00:00:00.04, start: 0.000000, bitrate: 1399811 kb/s
  Stream #0:0: Video: dirac, yuv420p(tv, bt470bg/bt709/bt709, progressive), 7680x4320 [SAR 1:1 DAR 16:9], 25 fps, 25 tbr, 1k tbn
    Metadata:
      ENCODER         : Lavc60.27.100 vc2
      DURATION        : 00:00:00.040000000
Stream mapping:
  Stream #0:0 -> #0:0 (dirac (native) -> mjpeg (native))
Press [q] to stop, [?] for help
[swscaler @ 0x5566938801c0] deprecated pixel format used, make sure you did set range correctly
    Last message repeated 3 times
Output #0, image2, to 'out.jpg':
  Metadata:
    encoder         : Lavf60.13.100
  Stream #0:0: Video: mjpeg, yuvj420p(pc, bt470bg/bt709/bt709, progressive), 7680x4320 [SAR 1:1 DAR 16:9], q=2-31, 200 kb/s, 25 fps, 25 tbn
    Metadata:
      DURATION        : 00:00:00.040000000
      encoder         : Lavc60.27.100 mjpeg
    Side data:
      cpb: bitrate max/min/avg: 0/0/200000 buffer size: 0 vbv_delay: N/A
frame=    0 fps=0.0 q=4.4 size=       0kB time=00:00:00.00 bitrate=N/A speed=N/A[image2 @ 0x55669385d980] The specified filename 'out.jpg' does not contain an image sequence pattern or a pattern is invalid.
[image2 @ 0x55669385d980] 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.
[out#0/image2 @ 0x556693852d40] video:190kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
frame=    1 fps=0.0 q=4.4 Lsize=N/A time=00:00:00.00 bitrate=N/A speed=   0x