Could not find encoder for codec id 27: Encoder not found

When attempting to output a video from the system (an mp4), on initialisation it prints the !!! TYPE message followed by Could not find encoder for codec id 27: Encoder not found then proceeds as normal.

At the end of processing it will error with AttributeError: 'NoneType' object has no attribute '__array_interface__'.

I believe this is caused by opencv-python pip package not being shipped with x264 (open-source h264 encoder), due to GPL issues? (see skvark/opencv-python#81)

Suggestion is to potentially catch this issue before processing lengthy videos. I did a search of the issues here and didn't find anything related, so hopefully there's enough here that others may find the reason for their issue.