elias@i7:~/code/ffmpeg/docker-images/4.1/ubuntu$ docker run -it --device=/dev/blackmagic:/dev/blackmagic -v /srv/assets:/srv/assets -v /etc/blackmagic/BlackmagicPreferences.xml:/etc/blackmagic/BlackmagicPreferences.xml flaneurtv/ffmpeg:snapshot-sdk-11.1 -f lavfi -i testsrc2=size=3840x2160:rate=25 -f decklink -pix_fmt uyvy422 'DeckLink 4K Extreme'
ffmpeg version N-93757-ge94447c Copyright (c) 2000-2019 the FFmpeg developers
  built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.11) 20160609
  configuration: --enable-decklink --disable-debug --disable-doc --disable-ffplay --enable-shared --enable-avresample --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-gpl --enable-libass --enable-libfreetype --enable-libvidstab --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx265 --enable-libxvid --enable-libx264 --enable-nonfree --enable-openssl --enable-libfdk_aac --enable-libkvazaar --enable-libaom --extra-libs=-lpthread --enable-postproc --enable-small --enable-version3 --extra-cflags='-I/opt/ffmpeg/include -I/tmp/blackmagic/include' --extra-ldflags='-L/opt/ffmpeg/lib -L/tmp/blackmagic/include' --extra-libs=-ldl --prefix=/opt/ffmpeg
  libavutil      56. 26.100 / 56. 26.100
  libavcodec     58. 52.100 / 58. 52.100
  libavformat    58. 27.103 / 58. 27.103
  libavdevice    58.  7.100 / 58.  7.100
  libavfilter     7. 50.100 /  7. 50.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  4.100 /  5.  4.100
  libswresample   3.  4.100 /  3.  4.100
  libpostproc    55.  4.100 / 55.  4.100
Input #0, lavfi, from 'testsrc2=size=3840x2160:rate=25':
  Duration: N/A, start: 0.000000, bitrate: N/A
    Stream #0:0: Video: rawvideo (I420 / 0x30323449), yuv420p, 3840x2160 [SAR 1:1 DAR 16:9], 25 tbr, 25 tbn, 25 tbc
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo (native) -> wrapped_avframe (native))
Press [q] to stop, [?] for help
[decklink @ 0x176b200] Found Decklink mode 3840 x 2160 with rate 25.00
Output #0, decklink, to 'DeckLink 4K Extreme':
  Metadata:
    encoder         : Lavf58.27.103
    Stream #0:0: Video: wrapped_avframe, uyvy422, 3840x2160 [SAR 1:1 DAR 16:9], q=2-31, 200 kb/s, 25 fps, 25 tbn, 25 tbc
    Metadata:
      encoder         : Lavc58.52.100 wrapped_avframe
[decklink @ 0x176b200] There are not enough buffered video frames. Video may misbehave!
    Last message repeated 6 times
[decklink @ 0x176b200] There are not enough buffered video frames. Video may misbehave!
    Last message repeated 5 times
[decklink @ 0x176b200] There are not enough buffered video frames. Video may misbehave!
    Last message repeated 6 times
[decklink @ 0x176b200] There are not enough buffered video frames. Video may misbehave!
    Last message repeated 6 times
[decklink @ 0x176b200] There are not enough buffered video frames. Video may misbehave!
    Last message repeated 6 times
[decklink @ 0x176b200] There are not enough buffered video frames. Video may misbehave!
    Last message repeated 6 times
[decklink @ 0x176b200] There are not enough buffered video frames. Video may misbehave!
    Last message repeated 6 times
[decklink @ 0x176b200] There are not enough buffered video frames. Video may misbehave!
    Last message repeated 6 times
[decklink @ 0x176b200] There are not enough buffered video frames. Video may misbehave!
frame=   84 fps= 13 q=-0.0 Lsize=N/A time=00:00:03.36 bitrate=N/A speed=0.509x    
video:44kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
Exiting normally, received signal 2.