Conversion failed after ffmpeg call

[wiederin]

When I run the command: ffmpeg -nostdin -threads 1 -i 'udp://@0.0.0.0:8554?overrun_nonfatal=1&fifo_size=50000000' -f:v mpegts -fflags nobuffer -vf format=yuv420p -f v4l2 /dev/video42
I get the error output:

ffmpeg version n4.3.1 Copyright (c) 2000-2020 the FFmpeg developers
  built with gcc 7 (Ubuntu 7.5.0-3ubuntu1~18.04)
  configuration: --prefix= --prefix=/usr --disable-debug --disable-doc --disable-static --enable-cuda --enable-cuda-sdk --enable-cuvid --enable-libdrm --enable-ffplay --enable-gnutls --enable-gpl --enable-libass --enable-libfdk-aac --enable-libfontconfig --enable-libfreetype --enable-libmp3lame --enable-libnpp --enable-libopencore_amrnb --enable-libopencore_amrwb --enable-libopus --enable-libpulse --enable-sdl2 --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libv4l2 --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-libxcb --enable-libxvid --enable-nonfree --enable-nvenc --enable-omx --enable-openal --enable-opencl --enable-runtime-cpudetect --enable-shared --enable-vaapi --enable-vdpau --enable-version3 --enable-xlib
  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
[h264 @ 0x5558233ad100] non-existing PPS 0 referenced
    Last message repeated 1 times
[h264 @ 0x5558233ad100] decode_slice_header error
[h264 @ 0x5558233ad100] no frame!
[h264 @ 0x5558233ad100] non-existing PPS 0 referenced
    Last message repeated 1 times
[h264 @ 0x5558233ad100] decode_slice_header error
[h264 @ 0x5558233ad100] no frame!
[h264 @ 0x5558233ad100] non-existing PPS 0 referenced
    Last message repeated 1 times
[h264 @ 0x5558233ad100] decode_slice_header error
[h264 @ 0x5558233ad100] no frame!
[mpegts @ 0x555823386a40] Could not find codec parameters for stream 2 (Unknown: none ([128][0][0][0] / 0x0080)): unknown codec
Consider increasing the value for the 'analyzeduration' and 'probesize' options
[mpegts @ 0x555823386a40] Could not find codec parameters for stream 3 (Audio: ac3 ([129][0][0][0] / 0x0081), 0 channels, fltp): unspecified sample rate
Consider increasing the value for the 'analyzeduration' and 'probesize' options
Input #0, mpegts, from 'udp://@0.0.0.0:8554?overrun_nonfatal=1&fifo_size=50000000':
  Duration: N/A, start: 159.360000, bitrate: N/A
  Program 1 
    Stream #0:0[0x1011]: Video: h264 (High) ([27][0][0][0] / 0x001B), yuvj420p(pc, bt709, progressive), 1920x1080 [SAR 1:1 DAR 16:9], 29.97 fps, 29.97 tbr, 90k tbn, 59.94 tbc
    Stream #0:1[0x1100]: Audio: aac (LC) ([15][0][0][0] / 0x000F), 48000 Hz, stereo, fltp, 196 kb/s
    Stream #0:2[0x200]: Unknown: none ([128][0][0][0] / 0x0080)
    Stream #0:3[0x201]: Audio: ac3 ([129][0][0][0] / 0x0081), 0 channels, fltp
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (native) -> rawvideo (native))
[swscaler @ 0x555823451a80] deprecated pixel format used, make sure you did set range correctly
[video4linux2,v4l2 @ 0x5558233d9740] Unable to open V4L2 device '/dev/video42'
Could not write header for output file #0 (incorrect codec parameters ?): Operation not permitted
Error initializing output stream 0:0 -- 
Conversion failed!

I can start the preview in vlc without any issues. Is there something that needs to be changed?