ffmpeg live feed input

List input devices:
ffmpeg -f decklink -list_devices 1 -i dummy
List supported formats:
ffmpeg -f decklink -list_formats 1 -i 'Intensity Pro'
Capture video clip at 1080i50 (format 11):
ffmpeg -f decklink -i 'Intensity Pro@11' -acodec copy -vcodec copy output.avi
Capture video clip at 1080i50 10 bit:
ffmpeg -bm_v210 1 -f decklink -i 'UltraStudio Mini Recorder@11' -acodec copy -vcodec copy output.avi
Capture video clip at 1080i50 with 16 audio channels:
ffmpeg -channels 16 -f decklink -i 'UltraStudio Mini Recorder@11' -acodec copy -vcodec copy output.avi

REF: https://ffmpeg.org/ffmpeg-devices.html