Exaile says I don have the needed decoder, or i might need plugins to play this file. What does that mean?
Due to licensing restrictions, several common formats such as MP3 and AAC are not natively supported by Exaile’s media backend, gstreamer. You can remedy the situation by finding and installing the appropriate gstreamer plugins to handle your formats. Common open-source gstreamer plugin sets are known as “-bad”, “-ugly”, and “-ffmpeg”, or for a closed-source (but more legally stable) alternative, the fluendo plugins can be used. Most linux distros include some if not all of these plugins in their software repositories, so check what your distribution has available before trying to obtain these via other means.
