Earlier quoted context omitted.
That’s not the legal criterion that’s used. Using a different codec is different that using the idea of a book to write your own book.
the "codec" is not really the point. playing an MP3 at a venue, streaming it or distributing it is a copyrighted act because, despite not being a verbatim copy of the original material, it is capable of producing a nearly-verbatim version of that intellectual property well enough that most people won't be able to notice the difference. similarly, as has been shown (by numerous publishers and authors), LLMs are capabl…
If that is true, you have a legal claim and can sue them. I doubt that’s true in the general case though.
The “does it hurt the original publisher” is a test for fair use BTW, just because you hurt the sales of someone doesn’t necessarily make it copyright infringement. That is only relevant if you try to defend using fair use (and it’s only part of the test that’s used to decide fair use).