mime-type is derived from the file extension, and the extension alone is often not enough to differentiate an audio from a video file.  There are many container formats that may or may not contain video tracks. E.G. a .webm file could be audio/webm or video/webm.  Hydra is just doing `MIME::Types.of('foo.webm')` and taking the first mime-type, this is not sufficient if you want valid metadata.