High latency is a surefire way to ruin a climactic moment in your favorite movies, TV shows, or games. Latency refers to the delay between the image on your TV and the audio coming out from your soundbar. It's most easily noticeable when characters talk on-screen, as their voices can be heard before or after their lips move, which can ruin the immersiveness of your media. Depending on the kind of wired connection you're using, you may experience different amounts of latency.
If you love to watch a lot of movies or TV shows, it's important to ensure that your audio is in sync with your video. When you have high amounts of latency, you can experience issues most noticeably in lip-synching: this is when voices don't match up with lip movement. Latency is also important for gamers, as out-of-sync audio or visuals can put you at a disadvantage if you're playing with other people. While wired connections can help reduce this issue, especially when compared to wireless connectivity options like Bluetooth, they can still have latency issues. As a result, some manufacturers like Samsung include an audio sync feature in their soundbars or TVs to counter this. However, we don't currently test the efficiency of these features in our soundbar tests.
The Latency test refers to the latency over three wired connections: ARC, Optical, and Full HDMI In. We connect the same Samsung Q80T TV with the desired soundbar and wired connection, so the results are comparable. A tripod with a camera phone is set up approximately 5.75ft away from the TV to film the results. We then play the audiovisual latency video seen down below on the TV and record the process.
In this video, there's an audible ping that occurs once every second. Each ping should ideally be in time with the moment the white ball touches the moving white platform at the bottom of the screen. At the same time, the left circle should alternate between green and white while the red circle on the right side appears. Our video is slowed down to 20% to more easily see the sound delay.
We measure latency in milliseconds (ms), and we consider a good latency value to fall between -55 ms to 75 ms.
However, as hinted above, latency can be measured in both positive or negative values. For example, The Vizio SB36512-F6 has an ARC latency of 75 ms. A positive latency value indicates that the visuals come before sound. Conversely, this same soundbar has -85 ms via its Full HDMI In connection. A negative latency value indicates that sound comes before visuals. A higher positive latency value is more acceptable than a higher negative latency value, as it's easier to notice sound coming before visuals than the other way around. For example, if you're watching a movie, you'll more likely notice the actor's voice before their lips start moving. When the results are more (or less) than -55 ms to 75 ms, you start to experience noticeable latency.
That said, latency results can vary depending on the frame synch between the 60fps YouTube video we use and our 240fps recording speed. However, if this test is performed multiple times, the difference is approximately 4-6 ms, which isn't very noticeable. Other factors like TV input lag fluctuation can influence latency. Some apps and devices also compensate for latency, so your experience may vary. Lastly, your equipment, like the device you're using to watch and listen to this test video, could have latency in itself and could change the perception of the video.
Note that our Reaper software was skipping frames, as its project settings were set at 30fps instead of 60fps. As a result, it was missing the 'ball on white bar' image that we use to measure the latency accuracy. Unfortunately, most of our test results could be off by potentially +/- 16.7 ms. We're currently working to address this issue.
HDMI ARC stands for 'Audio Return Channel'. It's a protocol introduced as part of HDMI version 1.4 in 2009, and since then, has become a somewhat common addition on soundbars. This connector allows audio signals to travel to and from the soundbar and eliminates the need for a secondary cable to send audio from your TV back to your soundbar. The protocol also adds HDMI CEC, which allows you to control HDMI-connected devices with one remote control.
Some soundbars also support eARC or 'enhanced Audio Return Channel', which allows the bar to play object-based surround signals and lossless formats such as Dolby TrueHD or DTS-HD MA, commonly found on Blu-ray discs. The HDMI Forum, a non-profit corporation that develops new versions of HDMI Specification, has also made 'Lip Sync Correction' mandatory on eARC, while it's only optional on ARC. This should ensure that video and audio are automatically in sync. In short, this connection is favorable if you like to watch very high-quality, surround content.
In the ARC Latency test, we connect the bar via HDMI ARC to the TV. Using the TV's YouTube app, we play the latency video.
Optical is also known as a S/PDIF connector. It uses waves of light within fiber optic cables to relay audio signals from a source like your TV to your soundbar and support surround sound up to 5.1 channels. However, they can only relay audio, and you'll need a different cable to transmit video between devices. That said, this connection is handy if you have an older TV or soundbar without an HDMI port.
In the Optical Latency test, we connect the bar via Optical In to the TV. Using the TV's YouTube app, we play the latency video.
If your TV or soundbar doesn't support HDMI ARC, some soundbars and TVs have a high-definition multimedia interface or HDMI connection, which can transmit uncompressed signals without a loss in quality. Unlike HDMI ARC, Full HDMI In can only receive audio. Some users prefer to connect devices like a Blu-ray player or console directly to the soundbar to play all sound codecs.
In the Full HDMI In Latency test, the soundbar and TV are connected to an HDMI splitter. The splitter takes the source device's signal and sends it to the other devices connected to it, which are the soundbar and TV. For our source device, we use our test PC, and we play the YouTube video. At the same time, we change the audio source on our PC to match the correct source on the soundbar.
Latency can really ruin a good movie, TV show, or gaming session. Luckily, depending on which connection you use to hook up your soundbar to your TV, you can minimize the risk of out-of-sync audio or video. Some TVs and soundbars also come with their own audio sync features to further improve their latency. At the end of the day, however, some apps and devices compensate for latency differently, so your real-world experience may vary.