How could I delete metadata (Artist, Comments, Copyright, Engineer, Keywords, etc.) from MP3 and AVI files?
I suppose you already know that ExifTool can't do this. I don't know much about the capabilities of other metadata editors, so I can't help here.
- Phil
For AVIs, your best bet is FFMpeg. See this SuperUser answer (https://superuser.com/questions/441361/strip-metadata-from-all-formats-with-ffmpeg) for details.
You can also use for MP3s (see this [StackOverflow answer (https://stackoverflow.com/questions/20193065/how-to-remove-id3-audio-tag-image-or-metadata-from-mp3-with-ffmpeg)), but there are probably better tools that specifically deal with MP3s. I often seen mp3tag (https://www.mp3tag.de/en/index.html) mentioned when it comes to dealing with MP3 metadata. Additionally, Windows can be used to clear metadata from some files, right-click -> Properties -> Details tab -> Remove Properties and Personal Information