Batch embed metadata (or create m4a) for all items possible?

[xcy7e]

In addition to #847 I wondered if it's possible to embed metadata and/or create .m4a-files for all items at once, or batch-wise.

It's possible for a single book, which is somewhat awesome. Is it possible to apply this for all items at once?
(Maybe using another tool out there?)

Is there a console command for abs that I can make use of using bash, or so?