Actor mouths pre-recorded dialogue or song with choreographed movement — saves time, guarantees consistent performance. Real-time ADR on camera.
The actor stands in front of the camera, the playback track is running — and they have to precisely match what they recorded in the studio beforehand. This is lip dubbing, and it's one of the most underestimated disciplines on set. You're not working with a live performance here, but with a blueprint. The audio is finished, the lip-sync has to be right, and the body movement follows an invisible score.
In practice, it works like this: The music or dialogue has already been recorded — in the studio, with better sound design, in ideal acoustics. Now your performer is on set, listening to the playback via a monitor or headphones, and has to synchronize their lips, mouth, facial expressions, and often their entire body language. This sounds easier than it is. The rhythm has to be right, the lip movements have to appear authentic, but at the same time be visible to the camera. You have to work closely — the focus puller needs precise information about the depth of field, because every head movement counts.
The big advantage: You save time. A complex singing scene where your star would sing live would kill you in the edit. Thousands of micro-pop artifacts, breathing sounds, pitch fluctuations. With playback sync, you have complete control. You press play, the actors perform, you roll multiple takes, and later you cut together the best video performance with the guaranteed clean audio.
Typical: Musicals, concert films, also reality scenes with diegetic music — whenever a character is supposed to sing and the sound design cannot be created live. The camera setup must enable this — a good viewing angle of the mouth and eyes, stable lighting, no distracting reflections on the lips (because every highlight will be visible in the edit). It also requires communication: The monitor with the playback must work smoothly, and the sound department must coordinate the track with the sound engineering.
Common mistake: Too visible miming along to the playback without real emotion. The lips move, but the eyes are empty. Good actors manage to build an inner performance while working to someone else's audio. This is technically — and psychologically — a different task than live speaking. You have to understand this and guide the performer, otherwise you'll see it later in the edit: artificial, staged, faked.