MusicBrainz Picard error tagging video files

Question

MusicBrainz Picard is an excellent music tagging tool, able to fingerprint audio, even in video files… in theory! It's just not being able to write the tags onto the video files, spewing this error instead (line numbers may vary):

E: 11:16:58 Traceback (most recent call last):
  File "picard/util/thread.pyo", line 46, in run
  File "picard/file.pyo", line 210, in _save_and_rename
  File "picard/formats/mp4.pyo", line 179, in _save
  TypeError: 'NoneType' object does not support item assignment

This has been ticketed on MusicBrainz's issue tracking system over a year ago, so I thought I'd see if anyone here might have a clue…

Answer 1

FIXED. The issue is with the files, not Picard. Rewrapping them with ffmpeg (no need to reencode) does the trick:

ffmpeg -i *.mp4 -c copy -y