How to Eliminate Audio Delay (Lip-Sync Issues) in Live Broadcasts

Overview

Lip sync or audio delay issues can be very frustrating but fear not, we’ll go over how to fix them! These issues can arise when audio and video are processed by your production system or reach it at different times. So in this guide, we’ll explain how to both diagnose and fix audio delays within streaming and broadcast, including setups using HDMI, SDI, PTZ cameras, NDI as well as hardware based encoders. 

Symptoms of Audio Delay

Typically lip sync issues are going to be the most common, if the speaker’s mouth moves before the sound is heard then you’re having lip sync issues. However, there are also other types of audio delays such as the audio leading actions by a noticeable amount, or if your livestream appears out of sync even when local monitoring seems correct.

Step-by-Step Instructions

1. Determine Whether Audio Is Early or Late

One of the ways to do this is by recording a short video where you get someone to stand in front of the camera and begin clapping or speaking. During the playback of the video, check whether the audio leads or lags.

If the audio is early, you will need to delay the audio.
If the audio is late, you will need to delay the video.

2. Add Audio Delay in Your Mixer or Encoder

Thankfully, most production tools, like OBS, allow for audio delay adjustment.

Here are some places you might be able to find the settings for these:

• Audio mixers: often under audio delay or delay compensation
• Hardware encoders: usually available in the audio input configuration
• OBS Studio: this can be found within Advanced Audio Properties as the Sync Offset adjustment

It’s best to start small and then fine tune as necessary, so start with a delay of 100 to 200 milliseconds and then add or subtract as necessary until you get the desired result.

3. Account for Camera-Related Latency

Sometimes it can simply be caused by how you have your camera connected to the production setup. Different connection types will have differing amounts of delay. For example, HDMI and SDI cables will often have very minimal latency meaning you likely won’t have much issues caused by them, while NDI, RTMP, and RTSP streams can add significantly more due to the fact that they are tied to a network which can add extra delay thanks to congestion or simply because of the distance the signal is being sent. If you want to mix IP video feeds with hardwired feeds then you might need to add some audio delay so that the feeds add up.

4. Reduce Video Latency at the Source

Often it can be worth it to check the camera or switcher for certain features that might be enabled that can introduce buffering. Some examples of these features would be frame sync or general buffering modes. Some models might have a low latency mode and in cases where you’re experiencing sync issues it might be worth enabling. 

5. Test and Fine-Tune

Finally once you’ve gone through all these steps, it’s time to loop back to step one and do another clap test! If everything looks good then congratulations, the problem is solved. If there are still some issues, then keep adjusting the delay until it all matches up. 

Troubleshooting Tips

• If audio is ahead of the video, increase audio delay.
• If video is ahead of the audio, reduce or remove buffer settings.
• Wired connections reduce latency more reliably than wireless or Wi-Fi links.
• Standardize all camera sources to the same resolution and frame rate whenever possible.
• Verify that all audio and video sources are enabled and routed correctly.