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Audio/Video Sync Tester - Online Lip Sync Check

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Audio/Video Sync Tester

Online Lip Sync Check & AV Delay Calibration

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Audio and video are perfectly aligned

0 beats played

Frequently Asked Questions

A lip sync check (or audio/video sync test) measures whether spoken words match the lip movements in a video. This online tool generates synchronized beeps and flashes so you can visually and audibly detect any timing mismatch — without uploading any footage.

Common causes include Bluetooth/Wi-Fi audio latency, incorrect sampling rates, video processing delays, streaming buffering, or device-specific issues. Even browser settings can introduce several milliseconds of delay.

Press Start Test. A red circle will flash on the screen while a short beep plays at the same interval. Watch and listen. If you notice the flash and beep are not simultaneous, adjust the Audio Offset slider until they feel perfectly aligned. The offset you choose is your personal device calibration.

This tool focuses on hardware/browser delay measurement. For true lip sync check of your own video, we recommend importing it into a video editor and manually measuring the offset. However, you can use the calibration number from this tool to adjust playback settings in your editing software.

A positive offset means the audio is intentionally delayed (sound lags behind the flash). A negative offset means the visual flash is delayed to simulate audio leading. After adjusting, you'll experience subjective perfect sync. You can note this value and apply it in media players or streaming software.

We use the Web Audio API for precise audio scheduling and requestAnimationFrame for visuals. Accuracy is typically within a few milliseconds on modern browsers. For professional calibration, a hardware AV sync analyzer is recommended.

Tip: Use wired headphones to minimize Bluetooth latency while testing.

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