Only fetch metadata for files without it

I’d like to have aTV only fetch metadata for files that do no have it.

Most of my library has metadata – I use an OS X app called iFlicks that adds iTunes-compatible metadata and cover art to video files. This works fine and is read properly by aTV Flash when I have metadata fetching turned off. However, if I turn fetching on, aTV will ignore the file’s metadata and find its own info and cover art, which is sometimes incorrect and slower. But I also have files with no metadata which I would want aTV to retrieve.