Zkusil bych něco takového:

ffmpeg -i input_file.mp4 -c copy -metadata title="Movie Title" -metadata author="Some Girl" output_file.mp4

dělá to bez rekódování.

Ještě jsem našel:

Can I delete metadata files?
Identifying and Removing Metadata

Right-click on the file. View its Properties. If there is metadata that you would like to remove, select the Details tab. Click Remove Properties and Personal Information.