How to post-process a saved video file?

[compilebunny]

Question

I am using mediamtx to save RTSP streams from a camera to a video file. MP4 files are generated using

  # Record streams to disk.
  record: yes
  playback: no
  recordPath: /files/video%whatever
  recordFormat: fmp4  
  recordSegmentDuration: defined_time_period

I want to post-process each resulting mp4 file as it is completed. I tried using

runOnRecordSegmentComplete: /bin/post-processing-program

but /bin/post-processing-program never gets run.

How can I post-process each video file that is recorded to disk?