Please note that using certain encoding/decoding technology in some countries without first paying the appropriate license fees may mean that you are infringing on various patent holders' rights. Please check out the situation in your country first.
Ots Studio can import and transcode to MP3 any audio for which you have a DirectShow Filter on your system. However, you must have already installed the LAME encoder to achieve MP3 encoding. If you don't already have the LAME encoder installed, see here.
Note: Files with DRM (Digital Rights Management) are not supported.