Automated dialogue replacement or Additional dialogue recording (ADR) is a film sound technique involving the re-recording of dialogue after photography, also known as "looping."
In conventional film production, a production sound mixer records dialogue during photography, but several uncontrollable issues, such as traffic or animal noise, during principal photography can cause the production sound to be unusable. This is also true for computer-generated imagery, since some of the "actors" were not actually present at the set.
When the film is in post-production, a Supervising Sound Editor or ADR Supervisor reviews all of the dialogue in the film and rules which actor lines will have to be replaced using the ADR technique.
ADR is recorded during an ADR session. An actor, usually the original actor on set, is called to a sound studio equipped with video playback equipment and sound playback and recording equipment. The actor wears headphones and is shown the film of the line that must be replaced, and often he or she will be played the production sound recording. The film is then projected several times, and the actor attempts to re-perform the line while watching the image on the screen, while an ADR Recordist records the performances. Several takes are made, and based on the quality of the performance and sync, one is selected and edited by an ADR Editor for use in the film.
