MP4 metadata tags

[Wayne-nulitics]

I would like the ability to add metadata tags to the MP4 file, on initialization or on CompletedFileWritingAction, similar to what is possible using https://ffmpeg.org/ffmpeg-all.html#Metadata-1

This does not have to be dynamic editable, just to be able to set it on initialization or on closing the file. This explains it a bit more: https://wiki.multimedia.cx/index.php?title=FFmpeg_Metadata