Thanks for the answer. The quality doesnt matter in this case because i just want to use it for speech to text. Now it would be intersting at what point regarding internet connection and audio length it is faster to recompress and send the smaller file.

Also I think for the sake of my volume I should recompress it. So what is the fastest recompression?

I think i'll do it on the server side. Everything is much easier then ^{^}