Record a clap, slate or any sharp sound-with-motion through your vMix chain, then drop the file here.
Everything runs in this browser — nothing is uploaded.
Record something with a sharp, visible sound — a hand clap, a clapper board, a drumstick hit — through the same vMix inputs you stream with, then open the recording here. The picture and the audio are decoded from the same file, so any offset you measure is exactly what your viewers hear.
Open the Audio Mixer, click the cog on the audio input, and adjust Delay (ms) in the General tab. If audio is early (negative offset), add that many ms of Audio Delay. If audio is late (positive offset), take that many ms away from the Audio Delay on that input.
A video mark can only be as precise as one frame (33 ms at 29.97 fps). A clap that happens between two frames shows the hands already together on the next frame, so the true event is up to one frame earlier than the mark. Average several claps to tighten the estimate, or use a higher frame rate recording.
| Space / K | Play / pause |
| ← → or , . | Step one frame |
| Shift + step | Ten frames |
| J L | Back / forward 1 second |
| V | Mark current frame as the video event |
| A | Mark waveform cursor as the audio event |
| [ ] | Nudge cursor ±1 ms (Shift = 10 ms) |
| P | Audition 400 ms of audio from the cursor |
| + − / wheel | Zoom waveform |
| Shift + wheel / drag | Pan waveform |
| Z / F | Zoom to marks / fit whole file |
| Enter | Save the current pair as a measurement |
| Click waveform | Place the audio cursor (video stays on its frame) |
| Shift + click waveform | Seek the video to that point |