A method of associating metadata with a media signal receives an identifier for the media signal, uses the identifier to look up metadata in a metadata database, validates the metadata by checking attributes of the media signal relative to at least a portion of the metadata to provide validated metadata; and provides the validated metadata to a requesting application. Related methods enable searching of metadata across metadata databases, routing metadata requests to the metadata databases, controlling access to and validating metadata for media content, and re-associating valid metadata with media content.