a) The video that fills a key. Also used to describe the key itself.

Insert for most keys is “self,” that is, a key that is filled with the same video that cuts the hole. Ampex switchers also allow “matte” fill with an internally generated color and “bus fill” where any bus source may be selected to fill the key. b) An edit mode meaning to record a new video over a certain section of an existing video where the entry and exit are both defined and no new time code of control track is recorded.