Any plug-in that would tell me what's the codepage of the mp3 is?
like utf-8, ANSI...

Thanks.

This is almost impossible to do reliably, since the same string could be valid in various codepages (it would just have a different meaning, or, if it's all ASCII characters, would be identical in many codepages). In most cases you should have some idea of what codepage the file is beforehand, and you can use the File Info "Override codepage" function to convert it.

One trick if you're absolutely stuck and have no idea what codepage something is: MS Office has a reasonably effective codepage guesser. To use it, open Notepad, copy some of the MP3 tags into a plain text file (the more text the better, just put one tag on each line), save it, and open the file with the Word (File -> Open -> File Type Text Files). It won't always be right, but it will give a "best guess" and the dialog will let you see what the file would look like with each codepage installed on your system. That will usually let you figure it out.