Glossary
Lip sync delay
A mismatch between audio and video timing, often just a few frames, that makes dialogue seem slightly out of sync with lips.
Lip sync delay happens when the audio and video paths in a home theater process signals at slightly different speeds, so sound arrives a fraction of a second before or after the matching picture. It is most noticeable during close-up dialogue, where even a delay as small as one or two frames can make speech look subtly out of sync with mouth movement in a way viewers immediately notice.
This usually happens because video processing, such as upscaling or HDR tone mapping inside a TV or projector, takes slightly longer than the audio path through a receiver or soundbar, which processes and outputs sound faster by comparison. Most receivers and some TVs include a lip sync or audio delay adjustment specifically to add a small, deliberate delay to the audio path to compensate.
A common mistake is assuming the source device is at fault and swapping streaming boxes or cables, when the delay is often introduced by the display's own video processing chain instead. If dialogue drifts out of sync, checking for a lip sync adjustment in the receiver or soundbar's audio settings menu is usually a faster fix than replacing hardware.