Like many others, I'm experiencing the dreaded audio synchronization drift issue. For me, the issue is even more pronounced than for others because my rtsp h.264 producing IP cam doesn't have audio, and I'm using my computer's line-in. So the audio comes in at realtime and the video from the ip-cam is already lagged ~1.5sec by default.
What I've noticed though is that as the stream progresses, the audio gets further and further out of sync. FAST. In just 3 minutes, the original 1.5sec difference between the audio and video becomes 5 seconds (eg. +3.5s, or ~ +1sec/60sec synch drift). Of course this makes everything unusable... and there really aren't a lot of options for capturing rtsp h.264 streams for live streaming to youtube....
i've literally altered every option in obs as well as within the vs plugin but to no avail. in the regular 'video' input source, there are two options---use buffering and the ability to output audio to stream only / output audio to desktop that people say between those two, they're able to fix their audio sync issues... but the vsp doesn't realllly have those options.
Also the VSP only accepts integer framerates whereas the regular video input source in obs supports decimal framerates. this is the one thing I haven't attempted test since i can't with VSP, even though I know I'm getting a steady 30 out of my ip cams. =/.