Make the clap test
Record locally in OBS, not a stream. Clap once, sharply and in view of the camera, at the start, and again at the end of a recording as long as your normal stream. Step through the file one frame at a time and count the frames between the frame where your hands meet and the start of the clap’s sound.
Which OBS control to use
Sound first means the picture is late, so the sound needs delaying: Audio Mixer, the source’s menu, Advanced Audio Properties, Sync Offset (ms). Picture first means the sound is late, so the picture needs delaying: a Video Delay (Async) filter on a webcam or capture source, or a Render Delay filter on other sources. Sync Offset and Video Delay (Async) go up to 20,000 ms; Render Delay stops at 500 ms. Sync Offset changes the stream and the recording, not what you hear through monitoring.
A gap that grows
If the end clap is further apart than the start clap, the offset grows, and no fixed value holds for a whole stream. Match the sample rates of OBS and every audio device (usually 48 kHz), then look for dropped frames and unstable USB before setting any delay. The audio sync guide has the order.
For the complete connection plan, use the streaming setup builder. You can keep older equipment in your plan.
Sources
- OBS Studio 32.2.2 source: interface labels (Advanced Audio Properties, Sync Offset)
- OBS Studio 32.2.2 source: filter names (Video Delay (Async), Render Delay)
- OBS Studio 32.2.2 source: Sync Offset range (-950 to 20,000 ms)
- OBS Studio 32.2.2 source: Video Delay (Async) range (0 to 20,000 ms)
- OBS Studio 32.2.2 source: Render Delay range (0 to 500 ms)
- OBS Knowledge Base: Audio Mixer Guide
- OBS Knowledge Base: Filters Guide