How to write metadata into images for Pixiv and how to convert Twitter MP4 to Webm

[xxpc9]

Still learning the syntax of this tool.

1. How do I write the title, tags, and comments metadata from Pixiv images to Image details?
   

2. How do I convert Twitter MP4 to Webm?

Thanks.

[mikf]

There is no native support for any of this, so
external tools run from an exec post processor
is the answer to both of your questions.

For 1) I do not what tool can write these fields. Maybe that's just EXIF data?
For 2) FFmpeg