Fix audio that is out of sync with the picture

Lips move and the words arrive a moment later. Distracting within seconds, and a few seconds to correct.

Why it happens

Usually the file: audio and video were muxed with a small offset, common in older rips and re-encodes. Sometimes it is the output path — Bluetooth headphones and speakers add latency of their own.

Nudging it into place

Audio delay shifts the sound earlier or later while the film keeps playing. Watch one line of dialogue and adjust until lips and words agree — the offset is constant, so fixing one line fixes the film.

It is remembered

The offset saves against that file, so you correct it once and never again.

Ruling out your headphones first

Before adjusting anything in the player, consider how you are listening. Bluetooth adds a delay of its own — often a tenth to a third of a second — which has nothing to do with the file and follows you from film to film. If the same offset appears on everything you watch, the headphones are the cause. Plugging in wired output for one minute confirms it.

A reliable way to judge the offset

Find a close-up where someone speaks clearly, and watch the mouth rather than listening. If the sound arrives after the lips move, the audio is late and needs pulling forward. Adjust in small steps while the film continues playing — a tenth of a second is perceptible, and most files need less than half. Trying to judge it during action or music is much harder than during plain dialogue.

When the gap grows as the film runs

A constant offset is a muxing error and one adjustment fixes it for good. A gap that widens over the film is a frame-rate mismatch introduced when the file was made, and no single offset will hold across two hours. In that case a different copy of the film is a faster remedy than fighting the one you have.

Worth knowing