Simple Explanation

Making sure that the sound matches the mouth movements on screen.

Concise Technical Definition

The synchronization of audio with video so that sound is heard at the correct time relative to visual events, especially speech.

Layman-Friendly Analogy

Like watching someone speak on a video and their voice matches their lips—if it doesn’t, it's like a badly dubbed movie.

Industry Usage Summary

In video production and home theater, lip sync issues arise when video processing delays image output; compensating with audio delay (typically 40 ms–80 ms) restores sync. AV receivers and broadcast gear often include adjustable delay settings for this purpose.

Engineering Shortcut

Audio delay to align with slower video stream; prevents mismatch.

Full Technical Explanation

Lip sync refers to the coordination of audio and video signals so that speech and visual events occur simultaneously as perceived by the viewer. In most modern video systems—especially flat-panel displays like LCD and OLED—video processing introduces latency, causing a mismatch where the sound is heard before the corresponding visual event. To correct this, systems apply a deliberate delay to the audio signal, typically in the range of 40 ms–100 ms, depending on frame rate and processing depth. For instance, a two-frame delay at 50 Hz is approximately 80 ms. Professional broadcast environments may require delays up to 8 frames to accommodate complex video effects chains. AV receivers, processors, and editing software often offer lip sync adjustment features to ensure proper alignment.