Currently in order to hide unsupported media types from my renderer (PS3) I have to enable the 'ignore-unknown' setting and then setup a large number of mappings between filetype extensions and mime types. In combination with bug #1771561 this can be painful.
I think it would be a better system to supply a list of mime types in the config that should be served by the server
e.g., audio/mpeg, audio/mp4, video/mpeg, video/mpeg2, video/mp4
Then filetype mappings can still be handled by libmagic but 'unsupported' files are hidden from the renderer.