Adding Metadata to .MP4 File

[GarbageHaus]

I am looking to add metadata to the .mp4 that is produced after using hv_generate_video.py.

Unless I've misunderstood something the PyAV seems to indicate that this library has no way to accomplish this currently. (PyAV-Org/PyAV#1601)

I think this can be accomplished using subprocess, but this is a messy solution. I'm not really sure what the best option here is since I don't want to introduce another 3rd party library nor have a library in the project that isn't going to be used.

[GarbageHaus]

See PR: #80

[kohya-ss]

I don't think adding a new library is desirable, and using ffmpeg to add metadata, if it's in our path, seems like a messy but practical solution.