I noticed in early 2025 that, when I used my USB external webcam together with OBS Studio for video sessions, that the video signal was falling gradually and increasingly behind my audio signal and, indeed, real time. Sometimes it took 10 minutes, sometimes it took an hour, but eventually, my video would become so far out of sync with my audio that it became too distracting to continue. Restarting OBS Studio brought the camera back in sync with my microphone.

The problem lay in buffering, so I turned it off, and now all seems well.

  1. In OBS Studio, open the Properties for your V4L2 Video Source.
  2. Look for the option Use buffering and unselect it. In OBS Studio 31, this is a checkbox, so uncheck it.

I don’t know whether you need to restart OBS Studio for this change to take effect, but you might.

With buffering off, my webcam has not (yet) fallen behind noticeably, even after over 90 minutes of continuous use on my laptop. If the symptom remains, it is much much much less noticeable.

A Fix?

The nice folks in the OBS Studio community are working on a fix as of July 25, 2025.

Key References

Some Details

First, the ingredients that led to the symptom:

  • OBS Studio 31.0.4 running on Flatpak
  • Anker PowerConf C200 external USB webcam connected by USB-A
  • Røde lapel microphone connected to an audio-to-USB adapter connected to an external (powered) USB hub connected by USB-A
  • The Zoom client for Linux
  • Pop!_OS 22.04

The symptom: the video signal echoed through OBS Studio and transmitted over Zoom gradually and increasingly fell behind real time, although my audio signal stayed very close (close enough!) to real time for me not to notice the difference. Video fell more and more out of sync with audio (and real time) without a clear pattern for when it would happen nor how much. I only knew that it happened increasingly, so that choosing a fixed audio offset would not solve the problem.

With all these variables, you can imagine how many permutations I had to test to gather information. Sometimes I could run my camera for 30 minutes and not notice a difference and sometimes I could run my camera 10 minutes and start seeing my video fall noticeably behind. As I was thinking about what could be happening, I was ruling ingredients out, such as Flatpak, the USB hub, the microphone, the webcam (my laptop’s internal webcam seemed fine), the Zoom client, the Zoom web app on Chrome, the current version of OBS Studio… it took weeks to gather enough information to be able to ask for help in a meaningful way.

Why not just use my internal webcam? Because on it I look pink like a lobster… part of the time. I like this external USB webcam precisely because it provides a nicer and more consistent picture.

Finally, I managed to point the finger quite strongly at OBS Studio, which led me to ask on the forum. It took nearly two weeks, but someone replied not only with a helpful idea, but with a very likely explanation for all the behavior I was seeing: OBS Studio was buffering the frames and insisting on displaying “out of date” frames rather than jumping forward to the front of the queue. When the computer was under heavier load, the frame queue kept expanding and OBS Studio kept insisting on displaying frames in sequence, rather than jumping forward. The issue seems to revolve around the difficult question of which timestamps to trust coming from which clocks.

Very well, then: turn buffering off, which results in perhaps dropping more frames, but eliminates the problem of never catching up to the front of the frame queue.

Presumably this buffering also affects my laptop’s internal webcam, but I presume that external webcams connected by an external USB port are more likely to be affected by variations in the computer’s workload. I suppose if I kept OBS Studio open for 24 hours and kept my laptop busy from time to time, even a buffered internal webcam video source might fall behind real time.

So there it is. I don’t know whether I will ever regret turning buffering off, but at least for now, my voice and my face are reunited, which is plenty good enough for today.