Use custom file fields

I'm just wondering wether it would be possible to make use of custom file fields. I can add fields to video file types (e.g. credits, custom thumbnail, ...) those will be available in the video field (e.g. inside a player template) but the user can not see/fill them when uploading a video inside a node/add
Using admin/content/file is no option here.
Media does somehow support it I guess- not sure what's necessary to get the custom fields show up on node/add or node/edit?!