I use MP3TAG to manage my Video MP4 because its the easiest. The problem I have had for a while is that information is in the %comment% field and I need to use Tag-Tag copy it to %podcastdesc% field it previews as blank.
Now if I manually enter information in %podcastdesc% I can see information.
the %podcastdesc%is the field Itunes and AppleTV use to show a description of the video or movie aka Plot
the %tvseason% and %tvshowepisode% are working fine
I can't reproduce this behaviour.
If I try to copy the content of COMMENT into the tag PODCASTDESC I can see the preview as expected:
How exactly (screenshot?) do you try it to get the preview as blank?
its actually the other way around. The %comment% has the data I want to move to %podcastdesc%
The Field PODCASTDESC in this Convert Tag->Tag case is the TARGET field.
The Format String combines existing SOURCE fields (or parts of the content of such source fields).