Audio

How to fix audio/video sync (lip-sync) problems in a church stream

Few things make a stream look amateur faster than audio out of sync with the video — the preacher's lips moving a beat off from their words. The good news: it's almost always fixable with a single offset setting once you understand where the delay comes from. Here's how.

Why sync drifts in the first place

Audio and video usually travel different paths to your streaming software, and those paths take different amounts of time:

• Video from a camera often passes through a capture card, a converter, or an NDI encode/decode — each adding a little delay.
• Audio from the mixing desk usually arrives more directly and therefore earlier.

The result: audio tends to lead the video slightly. Your job is to delay the audio just enough to match the picture.

Step 1: Confirm which is ahead

Watch the preacher's lips on your program monitor:

• If you hear the word before the lips move → audio is ahead (the common case) → add audio delay.
• If the lips move before you hear it → video is ahead → the fix is a small video delay (or reduce audio delay), less common.

Step 2: Add an audio offset

Both major tools have a built-in sync offset — no external gear needed:

In OBS: right-click your audio source → Advanced Audio Properties → set a Sync Offset in milliseconds (positive delays the audio). Start around 100–150 ms and adjust.

In vMix: open the input's settings and adjust the audio delay for that input until it lines up.

1. Add a small delayStart with ~100 ms of audio delay.
2. Watch the lipsNudge up or down in 20–40 ms steps.
3. Lock it inWhen consonants match the mouth, you're synced.

Step 3: Test on the actual stream, not just locally

Encoding and the platform can add their own buffering, so check the real output — watch your live stream on a phone (muted room to avoid feedback) and confirm sync there, not only in your preview.

When sync keeps drifting

If it won't stay locked:

• Free-running clocks. Cheap capture devices can drift over a long service. A better capture path helps.
• Wireless audio. Some wireless systems add variable latency; test with them in the chain.
• Wi-Fi video/NDI. Move NDI over wired gigabit — Wi-Fi jitter causes inconsistent delay.
• USB overload. Too many devices on one bus can hiccup; spread them out.

Sync isn't just for cameras

Any element with its own path can drift — graphics and lower-thirds included. Because scripture overlays from TajiCast are sent over NDI as part of your production, they sit in the same synced pipeline as your other sources, so the verse lines up with what's being said.

A repeatable pre-service check

1. Point a camera at someone talkingIdeally the preacher at the podium.
2. Watch lips on the program feedJudge whether audio leads or lags.
3. Dial the offset and verify on a phoneConfirm on the real stream before you go live.

For getting the audio itself clean before it ever hits the sync stage, see great audio for your church live stream.