ADR

ADR (Automated Dialogue Replacement), also called looping, is the process of re-recording dialogue in a controlled studio when the original on-set audio is unusable, whether from noise, overlapping sound, or a line change. The actor watches the picture and listens to the original take through headphones, then performs the line again in sync with their lip movements. A dialogue editor and mixer then place the new recording precisely against picture and blend it so the studio take matches the perspective, room tone, and tone of the surrounding scene. The hard part is making clean studio audio sit naturally in a real environment, which means matching reverb, EQ, and ambience so the swap is invisible. Good ADR rescues otherwise unusable performances and is standard practice on most film and television.