In the case of live concert performances, lip-synching is done by some singers to ensure that the vocal performance will sound as good as the CD, but it can be considered controversial, especially if the audience believes that they are viewing a live singing performance. In film production, lip synching is often part of the post-production phase. Dubbing foreign-language films and making animated characters appear to speak both require elaborate lip-synching. Many video games make extensive use of lip-synced sound files to create an immersive environment.
Contests and game shows
In video games
Television transmission synchronization
(source : wikipedia)