I noticed a lot of different questions about the subject MP3 in the legal website (https://law.stackexchange.com/search?q=mp3). But none of them answer my question really.
First of all, I'm thinking about including features in a technical service that should be compatible with MP3 files. This means I would like to know if it is legal for me decode and use a user-uploaded MP3 file. For example; converting it into another audio format. Or make an image of the frequency waves within that MP3 file. Is it I allowed to work with the MP3 format without paying a license fees?
Secondly, is it also allowed to encode an audio file into the MP3 format. For example a text-to-speech tool that outputs the audio in an MP3 encoded file.
So shortly; Can I legally use (read/encode to/decode from) the MP3 format without paying a license fee?