Lip sync, also known as audio to video synchronization, refers to the matching of lip movements to live or recorded video, and it’s a critical element for good user experiences. Have you ever tried to watch a clip or a TV show where the lip sync wasn’t quite matching up? It’s frustrating and distracting, and you probably had to shut it off.

Ideally, lip sync should be within +45 to -125 milliseconds for most people not to notice. In general, if the audio is offset by more than 200 milliseconds, people definitely notice and start to twitch a little. Our brains are at least two times more sensitive to early audio than to late audio. That’s because audio doesn’t come before video in the natural world. Do you see lightning first, or hear the crack of thunder? The slow speed of sound relative to the speed of light has conditioned us to expect to hear the audio after we’ve seen the corresponding event .

The most unsettling lip sync errors may be the ones we can’t “see.” For most viewers, if the audio is between 45-25 milliseconds early and 90-125 milliseconds late, the brain does not consciously register a lip sync error. However, studies have indicated that synchronization offsets in these bands can have the subconscious effect of making the program material seem less believable and therefore less trustworthy.

Dynamic Delay EQ to the Rescue!
Audio and video streams typically have significant differences in latency, so maintaining lip sync can be inherently challenging. Exacerbating the issue is the fact that pro AV installations frequently involve separate audio processing and video distribution systems. Thus, synchronizing audio and video signals that are transmitted and processed separately can range from difficult to apocalyptic because the two systems aren’t “aware” of one another’s processing times and don’t have a common master clock. Often, these factors can cause problems with phasing, echoing between output devices, and the occasional bout of mass hysteria triggered by audio and video signals that are wildly out of alignment. Introducing manual delays in each signal path is the usual approach for fixing sync problems. However, that takes significant time during commissioning, and if anything changes in the system after it’s deployed (users never connect their own devices, right?), all your hard work is ruined. Yuck.

Luckily, Tesira manages the entire audio and video signal path for you. Tesira’s built-in processing algorithms understand exactly how long it takes each signal to pass through every device and over the network, allowing it to precisely synchronize everything. The result is TesiraLUX’s robust, integrated lip sync management that synchronizes audio and video output within 20 milliseconds or less. We call this Dynamic Delay Equalization. Patented by Biamp, this technology enables Tesira to dynamically detect changes in the propagation delay of each audio and video signal path and automatically adjust on the fly to keep every signal time aligned. So, go ahead and process, route, combine, or separate the audio and video streams at will — we’ve got you covered.

Learn more about TesiraLUX, lip sync, dynamic delay EQ, and their impact on your video installations. If you’re ready to see TesiraLUX in action, you can also contact your Biamp sales representative to schedule a demo.