Troubleshooting
Why Your Audio and Video Drift Out of Sync
Sound that starts right and slowly slides is a different fault from sound that is offset from the first frame. Knowing which one you have tells you how to fix it.
2 min read · Published 5 September 2026
There are two different faults here and people describe both as out of sync. Telling them apart takes ten seconds and saves an hour, because the fixes have nothing in common.
Play the first second, then skip to the last minute. If the gap is the same in both places, the audio is offset. If it is small at the start and large at the end, the audio is drifting.
A constant offset
The sound is simply early or late by a fixed amount, usually a fraction of a second, and stays that way throughout. This comes from recording chains where the picture and the sound took different paths: a Bluetooth microphone with its own latency, a capture card buffering frames, a phone recording the screen while the audio comes from the system mixer.
The fix is one number. Shift the whole audio track by the measured offset in any editor and the file is correct from end to end. Measure it once, on a moment with a sharp visual and audio cue, like a clap or a door closing.
A growing drift
This one is a clock problem. The picture and the sound were recorded against slightly different ideas of how long a second is, so a tiny error repeats every second and accumulates. Half a frame a minute is invisible for the first two minutes and a disaster by minute thirty.
The common causes are variable frame rate recordings, which phones and screen recorders produce by default, and files whose audio sample rate was assumed rather than read.
| Symptom | Likely cause | Fix |
|---|---|---|
| Same gap throughout | Recording latency | Shift audio once by the measured amount |
| Gap grows steadily | Variable frame rate | Convert to constant frame rate first |
| Gap grows after an edit | Mixed frame rates in one timeline | Set the sequence rate to match the footage |
| Sudden jump mid file | Dropped frames while recording | Re-record; this cannot be corrected cleanly |
Variable frame rate is the single most common cause of drift in screen and phone recordings. The file says thirty frames a second as an average, while the actual gap between frames changes with how busy the machine was. Editors trust the average, and the error accumulates from there.
Finding out which one you have
Read the file rather than guessing. The video file info tool on this site reports the frame rate the file declares and the audio sample rate alongside it. A recording that reports a frame rate with a long decimal, or one where the average and the real rate disagree, is a variable frame rate file and will drift.
If it is variable, convert the whole file to a constant frame rate before you edit rather than after. Fixing drift once it is baked into an export means re-stretching audio, which changes its pitch unless done carefully, and is always worse than converting the source.
Avoiding it next time
- Record screen capture at a constant frame rate if the software offers the choice
- Use wired audio where latency matters, or record a clap at the start so any offset is measurable
- Keep everything in one project at the same frame rate rather than mixing 30 and 29.97
- Check a long recording at both ends before you start cutting, not after
Common questions
Why does my audio slowly get ahead of the video?
Almost always a variable frame rate recording. The file declares an average frame rate, the real gap between frames varies with system load, and the editor trusts the average. The small error repeats every second and accumulates into a visible drift by the end of a long recording.
What is the difference between an offset and a drift?
An offset is the same size at the start and the end, and is fixed by shifting the audio once. A drift grows as the file plays, and shifting will not fix it because the error is proportional to time rather than constant.
Can sync be fixed after exporting?
An offset can, by shifting audio in a new pass. A drift is much harder once exported, because correcting it means stretching the audio over the full length, which affects pitch unless the tool compensates. Converting the original source to a constant frame rate and editing again gives a better result.
Does re-encoding fix sync problems?
Only if the re-encode converts a variable frame rate to a constant one. A straight copy of the streams preserves the fault exactly, which is why a file that drifts still drifts after a quick format change.