Audio drifts out of sync during long recordings
Sound and picture start together and separate over time. Usually clock drift between capture devices, a variable frame rate source, or a saturated recording drive.
Published
Constant offset versus growing drift
A constant offset that never changes is device latency. Fix it once with the sync offset field in Advanced Audio Properties. Drift that grows over a long session is a different problem: two devices are running on slightly different clocks, and the gap accumulates.
Fixing drift
- Set every audio device to the same sample rate as OBS (Settings → Audio → Sample Rate). A microphone at 44.1 kHz feeding a 48 kHz pipeline is resampled continuously, and resampling is where drift appears.
- Avoid using a USB capture card's audio and a separate USB microphone as independent clocks over multi-hour sessions where you can route both through one interface instead.
- Check the Stats dock for skipped or missed frames. A recording that is quietly dropping frames will look out of sync even though the audio is correct.
Variable frame rate output
If the recording plays in sync in one player and drifts in an editor, the file is probably variable frame rate. Record MKV and remux to MP4 from the OBS File menu, and make sure the recording drive can sustain the write rate you are asking for. A drive that stalls forces OBS to write frames late, which is stored as timing irregularity in the file.
Repair an existing file
An already-recorded file with constant offset can be corrected in any editor by shifting the audio track. Growing drift needs the audio stretched rather than shifted, which is why fixing the capture chain is worth more than fixing individual recordings.