I used id3v2 with this command
for i in *.mp4; do id3v2 --artist "Artist Name" "$i"; done
with the intention to populate the otherwise empty tag fields of some mp4 videos in a folder. It worked with the mp3 files but it rendered the videos unplayable. Using a simple
ffmpeg -i unplayable.mp4 restored.mp4
returned
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x55b02df528c0] Format mov,mp4,m4a,3gp,3g2,mj2 detected only with low score of 1, misdetection possible!
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x55b02df528c0] moov atom not found
unplayable.mp4: Invalid data found when processing input
Also trying to strip all the id3 tags didn't help.
My guess is that id3v2 somewhat messed up the file headers and it should be easy to restore them. However googling the problem reveals a carnival of software solutions, shareware, online services and such dedicated to repairing mp4 files hence my post here.