That's a configuration problem, and not hard to correct. Tell him to go into the audio settings, then "advanced audio settings", and add the "sync offset" in milliseconds required to bring the audio and video into sync.
Also, it's likely that his camera is mostly at fault; OBS with my Logitech camera doesn't have any significant lag. OBS itself has very little lag.
That’s desync, not latency/lag. They’re different things, and this solution will actually make the lag worse as it deepens the buffer. OBS virtual cameras definitely have noticeable lag with most people I have seen using them on Teams/Zoom.
I've experimented with OBS at well and decided not to use it for this specific reason. The lag is kinda subtle but on the other side of a test call (with someone else at my own desk) I was able to notice it quite well in interactions and it felt kinda annoying. Since I want the whole thing to feel as natural and positive as possible for the lager end, that was a non-starter. I can do without multiple cameras and gimmicky be-right-back screens.
The meaning of lag is notoriously varied--I think GP understood it as a consistent delay, and you and GGP are saying that OBS introduces an inconsistent delay, i.e., dropped frames or stuttering. The one using the virtual camera should be able to diagnose through the stats 'Frames missed due to rendering lag', 'Skipped frames due to encoding lag', and 'Dropped Frames (Network)', unless the virtual camera driver is somehow the culprit.
Or does one of you mean that even the constant delay is significant enough to be noticed on top of the video call latency?
I just realized that I don't know how the missed/skipped counters are actually defined--presumably frames are skipped for encoding if the encoder can't keep up with the framerate and missed for encoding if if any other part of the pipeline preceding it cannot.
> Or does one of you mean that even the constant delay is significant enough to be noticed on top of the video call latency?
That's what I meant. Video call latency is noticeable but in most cases is not detrimental to conversation (or I have gotten used to mentally correcting for it). Colleagues who have used virtual webcams often have a noticeable additional 100-300ms steady-state latency which goes over the threshold for easy conversation, for me at least.
Also, it's likely that his camera is mostly at fault; OBS with my Logitech camera doesn't have any significant lag. OBS itself has very little lag.