[FFmpeg-user] Help with metadata writing (mp4)... what's possible?

Gyan Doshi gyandoshi at gmail.com
Thu Dec 6 20:48:36 EET 2018

On 07-12-2018 12:10 AM, Karen Norton wrote:

> My questions are about finding the full scope of keys that can be written
> with ffmpeg because the sites I reference give varying sets of keys. I
> would like to find a comprehensive list of keys for all files in general
> (video and audio) but for mp4 in particular. I would also like to know
> about writing custom tags/keys. Is this possible for mp4 in general but
> more importantly mp4 with ffmpeg. :-D

The MP4 file format itself does not provide any restrictions on metadata 
keys. The list in my SU answer lists all the iTunes tags that our muxer 
currently supports. Custom global tags are possible if

    -movflags use_metadata_tags

is added to the command.

Then -metadata somekey=somevalue can be stored. I should update my 
answer to reflect this. I can't test this but it's possible that Apple 
applications may not read these or any other tags if this method is used.


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