the part of film or video production taking place after all the scenes have been shot, during which the final version of the film or tape is edited, the soundtrack is mixed, and music and special effects are added
See postproduction in American Heritage Dictionary 4
(pōstˌprə-dŭkˈshən)
noun
A final stage in the production of a film or a television program, occurring after the action has been filmed or videotaped and typically involving editing and the addition of soundtracks.