AV Sync Test
Calibrate audio/video timing with a synchronized flash-and-beep reference and millisecond-to-frame conversion.
Test settings
Microphone return estimate
Optional acoustic loopback estimate for the speaker-to-microphone path.
Recent calibration history
Stored only for this browser session.
No calibration history yet.
An AV Sync Test helps you check whether sound and picture are reaching you at the same time. When audio arrives before or after the visual event, speech can feel unnatural, lip movements may not match dialogue, and gaming, streaming, editing, or home-theater playback can feel noticeably out of sync.
Use the AV Sync Test above to compare a synchronized visual flash with a short test beep. You can then adjust the audio offset in milliseconds until both events appear aligned. The tool also converts your offset into frames, making it useful for TVs, soundbars, projectors, capture cards, OBS setups, Bluetooth devices, and video-production workflows.
If you are troubleshooting a broader delay problem, start with our guide on why audio is delayed to understand the most common causes across devices and playback chains.
How to Use the AV Sync Test
Start by choosing the frame rate that matches your playback or production setup. Common options include 23.976, 24, 25, 29.97, 30, 50, 59.94, and 60 FPS.
Then:
- Choose a visual mode such as flash, scanner, or flash plus scanner.
- Set the test interval and tone frequency if needed.
- Start the AV Sync Test.
- Watch the visual reference and listen to the beep.
- Adjust the audio offset until the beep appears to occur at the same moment as the flash or scanner reference.
- Use the fine-adjustment buttons for smaller changes.
- Review the offset in both milliseconds and frames.
- Use fullscreen mode when testing a TV, projector, or large display.
A positive value means the tool is delaying the audio relative to the visual event. A negative value means the audio is being advanced.
If you are also investigating general playback latency, compare your setup with the Audio Latency Test, which focuses on the full acoustic output-to-input path rather than visual synchronization.
How the AV Sync Test Works
The tool creates a repeating timing reference using two events:
- a visible flash or scanner marker
- a short audio beep
The goal is to make both references appear simultaneous.
If the beep seems to happen after the visual event, audio is effectively late. If the beep appears to happen before the visual event, audio is effectively early.
You can compensate by adjusting the offset until the two references feel aligned.
This is different from measuring raw audio latency. AV sync involves the relative timing between the video path and the audio path, and both can introduce processing delays.
Video delay may come from scaling, frame interpolation, image enhancement, refresh processing, decoding, or display buffering. Audio delay may come from Bluetooth, HDMI processing, soundbars, AV receivers, operating-system buffers, or software.
For deeper background on how users perceive timing differences, see our guide to audio latency perception.
Understanding Audio Early and Audio Late
AV sync problems become much easier to fix when you identify which side is ahead.
Audio late means the visual event happens first and the sound arrives afterward.
Audio early means you hear the sound before the visual event appears.
The direction matters because the correction you apply must match the problem.
In this tool:
- Positive offset delays audio.
- Negative offset advances audio.
- 0 ms means no additional manual correction is being applied.
The tool should be used as a calibration reference rather than as proof that every component in the signal chain is perfectly synchronized.
Milliseconds vs Frames
AV synchronization can be described in milliseconds or frames.
Milliseconds are useful for audio devices and playback settings, while frames are often easier to work with in video editing, broadcast workflows, capture software, and OBS.
Frame duration depends on frame rate.
For example:
| Frame Rate | Approx. Duration of One Frame |
|---|---|
| 24 FPS | 41.67 ms |
| 25 FPS | 40.00 ms |
| 30 FPS | 33.33 ms |
| 50 FPS | 20.00 ms |
| 60 FPS | 16.67 ms |
That means an offset of about 33 ms is roughly one frame at 30 FPS but about two frames at 60 FPS.
The AV Sync Test converts the offset automatically so you do not have to calculate the relationship manually.
Testing a TV, Soundbar, or AV Receiver
Home-theater systems can introduce AV sync problems because audio and video may travel through different processing paths.
A typical chain might include:
TV → HDMI → soundbar → audio processing
or:
Streaming device → AV receiver → TV
Video processing inside the television can add delay, while the soundbar or receiver may introduce a different amount of audio processing.
Use fullscreen mode and sit at your normal viewing position. Adjust the offset until the flash and beep appear aligned.
If your setup uses HDMI ARC or eARC, our guide to HDMI audio latency can help you identify where delay may be introduced.
Bluetooth and Wireless AV Sync
Bluetooth audio often introduces more latency than a direct wired connection because the signal may be encoded, transmitted wirelessly, buffered, decoded, and processed before playback.
This can create noticeable lip-sync issues, especially on devices that do not automatically compensate for Bluetooth delay.
If you are testing headphones or wireless speakers, compare your result with our Bluetooth Latency Test and read the explanation of Bluetooth audio latency.
For useful troubleshooting, test the same video first with wired audio and then with Bluetooth. The difference can help reveal whether the wireless path is contributing significantly to the sync problem.
OBS, Capture Cards, and Streaming
Streaming setups are another common source of AV mismatch.
A camera feed may arrive through a capture card while microphone audio enters through a separate USB interface or another device. Because those paths are different, they may not reach OBS at the same time.
You can use this AV Sync Test as a timing reference while adjusting synchronization values in your streaming setup.
If you use a capture device, see our guide to capture card audio latency. For streaming-specific adjustments, our OBS audio latency guide explains common causes and correction strategies.
Optional Microphone Estimate
The tool may also provide an optional microphone return estimate.
This mode plays a test sound and listens for its return through the microphone. Several measurements can be combined to show a median, average, and variation.
This is useful for identifying the acoustic playback path, but it should not be confused with direct video latency measurement.
The microphone cannot determine exactly how long your display took to show a frame. It measures the returned sound path, so treat this feature as additional diagnostic information rather than a complete AV synchronization measurement.
Accuracy and Limitations
Browser-based AV sync testing is useful for troubleshooting and practical calibration, but it is not laboratory equipment.
Results can be affected by:
- browser scheduling
- display refresh timing
- video processing
- operating-system audio buffering
- Bluetooth transmission
- HDMI processing
- AV receiver DSP
- soundbar processing
- frame interpolation
- microphone placement
- speaker distance
- background noise
A manual flash-and-beep test also depends partly on human perception.
For professional broadcast, certification, or engineering measurements, dedicated hardware and high-speed measurement tools may be more appropriate.
If your setup continues to behave inconsistently, review our guide to common audio latency problems and the site troubleshooting guide.
Privacy and Local Processing
The main flash-and-beep test runs locally in your browser.
Microphone access is only needed if you choose the optional microphone estimate. Audio analysis for that feature is used during the browser session to detect the returned test signal.
The tool does not need microphone access for manual AV offset calibration.
Frequently Asked Questions
What is an AV Sync Test?
An AV Sync Test helps you compare audio timing with a visual reference so you can identify whether sound is early, late, or approximately aligned with video.
What does a positive AV offset mean?
In this tool, a positive value means audio is delayed relative to the visual reference.
What does a negative AV offset mean?
A negative value means audio is advanced so it plays earlier relative to the visual reference.
How many milliseconds is one frame?
It depends on frame rate. At 60 FPS one frame is about 16.67 ms, while at 30 FPS one frame is about 33.33 ms.
Why is my TV audio out of sync?
Possible causes include video processing, HDMI devices, soundbars, receivers, Bluetooth audio, streaming hardware, or different audio and video processing paths.
Can I use this AV Sync Test for OBS?
Yes. The tool can provide a repeatable timing reference while you adjust audio synchronization settings in OBS or another streaming application.
Can it measure Bluetooth lip-sync delay?
It can help you observe the combined AV mismatch when Bluetooth is part of the playback chain, but it cannot isolate the Bluetooth codec from every other source of delay.
Is the microphone measurement the same as AV sync?
No. Microphone mode estimates the acoustic audio return path. It does not directly measure display or video-processing latency.
Why should I test more than once?
Browser timing, device buffering, display behavior, and other processing can vary slightly between tests. Repeating the calibration helps you determine whether the problem is stable or inconsistent.