Audio and video out of sync: causes and the 30-second fix

What "in sync" means

Video is a sequence of pictures; audio is a stream of samples. The player must present each frame at the right moment relative to the audio clock. Sync problems appear when the two clocks disagree — and the tolerance is small: most people notice a mismatch of about 100 ms, and anything over 200 ms is obvious.

Cause 1: the file's audio offset (most common with downloads)

Rips and remuxes sometimes carry an audio delay of 100–500 ms. This is in the file itself: no player can fix it automatically, because there is no "correct" answer — the file simply has the audio track starting early or late. The fix is an audio delay offset in the player.

In PurePlay: open the player → audio menu → Audio delay. Each tap is 0.5 s; positive values delay the audio. Adjust once and the whole film is in sync.

Cause 2: the player's rendering pipeline

On some devices the audio output has latency that the player must compensate for. Bluetooth headphones add 100–250 ms of their own (SBC/AAC codec buffering). A good player applies an audio output latency compensation; a naive one does not, and lip-sync is off only when using headphones. If the film is in sync on the speaker but not with Bluetooth, that is the cause — and it is not fixable from the file.

Cause 3: decoding fallback

When a hardware decoder fails and the player falls back to software mid-file, the two streams can drift apart for a moment. A good engine re-syncs to the audio clock. If you see a one-off jump where the audio is suddenly ahead, pause and resume once; if it recurs, switch decoding to software for the whole file.

The 30-second fix

1. Pause at a scene with clear lip movement.
2. Note whether sound is early or late.
3. Open the audio delay control and tap until the lip-sync matches (0.5 s steps).
4. Positive = audio later, negative = audio earlier.
5. Reset when you change file — the offset is per-file, not global.

What not to do

• Do not re-download the whole film because the first 200 ms are off — check the audio delay first.
• Do not adjust device-wide audio settings; the problem is per-file.
• Do not use "fix sync" apps that re-encode the file; a remux with -c copy is lossless and takes seconds.

Subtitle sync and audio sync are different

Subtitles follow their own timestamps. If the subtitles are off but lip-sync is fine, you need the subtitle delay control, not the audio delay. See the subtitle sync guide for that case.

When it is the device

Some Android skins apply a global audio effect chain that introduces latency — often a "sound enhancement" or "audio spatialisation" feature. If every video app is slightly out of sync with Bluetooth, turn those effects off and test again. This is outside the player's control.

Summary

• Constant offset → audio delay control in the player (positive = later).
• Only with Bluetooth → headphone/codec latency, not the file.
• Sudden jump mid-film → decoding fallback; try software decoding.
• Want a permanent fix → remux with FFmpeg and -c copy.