FFMPEG does not necessarily provide video_info["duration"] for video stream files

[DaveDuck321]

Example traceback for an mkv file generated using OBS "Record to File":

...
File "hackcambridge2022/src/video_processor.py", line 30, in __init__
  if float(self.video_info["duration"]) > 120:
KeyError: 'duration'

[antroseco]

Does this work? (https://superuser.com/a/945604)
ffprobe -v error -select_streams v:0 -show_entries stream=duration -of default=noprint_wrappers=1:nokey=1 input.mp4