"Automated" or "Automatic" Dialog Replacement

Dialog that cannot be salvaged from production tracks must be re-recorded in a process called looping or ADR.

Looping originally involved recording an actor who spoke lines in sync to "loops" of the image which were played over and over along with matching lengths of recording tape.  ADR, though faster, is still painstaking work.

An actor watches the image repeatedly while listening to the original production track on headphones as a guide.  The actor then re-performs each line to match the wording and lip movements.  Actors vary in their ability to achieve sync and to recapture the emotional tone of their performance.

ADR is usually considered a necessary evil but there are moments when looping can be used not just for technical reasons but to add new character or interpretation to a shot.  Just by altering a few key words or phrases an actor can change the emotional bent of a scene.