Lip Sync

Two situations get called this. First, syncing separately recorded audio to camera footage, done with a clap, waveform matching or the automatic sync in your editing application. Second, drift, where picture and sound start together and gradually separate over a long take. Drift usually comes from variable frame rate footage out of a phone or screen recorder, or from two devices whose clocks run at very slightly different speeds. The fix is converting to a constant frame rate before you edit, rather than nudging the audio and hoping. Audiences spot sound arriving ahead of the picture far sooner than sound arriving late, so err towards late.