Bluetooth is an ever-evolving tech with versions and variants popping up each year, and even third-party enhancements making older versions just as viable as newer ones! In among all this are some key specifications; things like the range of the connection, the "strength" or capacity of the connection and, importantly for this article,latency.
You'll see latency listed in specifications for all kinds of wireless devices, from headphones to car stereo adapters, and even the scoreboard in a multiplayer videogame! Understand what latency is, why it matters, and how to get the best wireless devices for less money by prioritising features well!
What is Latency?
Latency is a term used to describe an attribute of wireless devices. Latency describes the time it takes fora wireless signalto reach the target. Any device which connects wirelessly has to send its data through the air via technologies like radio-waves, infrared or networks like narrow-band mobile towers.
For example if you press "Shutdown" on your TV remote the signal is sent via infrared to the TV and then the TV processes the signal and shuts down. This is why you can experience input-delay or input-lag, as the travel-time combined with the processing time causes the command to not be instant.
Latency is measured in Milliseconds ordinarily, as it is very rarely very long. If you can measure the latency of a device in full seconds then the wireless connection is generally being interfered with! So, milliseconds or "ms" are used to simplify the measurement and present a nice, round number.
Some common examples of latency are:
- Using an IR TV Remote from Across a Room and Having Input Lag
- Speaking in a Skype / Zoom Meeting and it sounds like you spoke over / interrupted someone because you had not heard them speak yet due to latency, and vice versa
- Having desynchronisation in a videogame or stream with other players as the internet, servers and game processes all stack up latency creating input-lag
- Pausing, Playing and Skipping tracks on Bluetooth Headphones or a Bluetooth Speaker will occur slightly after you press the command on your phone / PC / Player
What is a Good Latency?
As mentioned above, latency is measured in Milliseconds. This gives a clue about the expected ranges of latency as usually we'd default to full seconds.
An important thing to remember; Lower Latency = Better Latency, this is not a case of wanting higher numbers! The lower the latency, the faster the connection.
Latency in modern Bluetooth 5.0 + devices can reach as low as 40ms natively. This means the signal is sent from the device to the receiver in 40 milliseconds or 0.04 seconds. As you can see, "0.04" is a bit clumsy so 40 milliseconds is used instead.
Open your phone's stopwatch and try to stop it before it reaches 0.04! (Okay, most phones don't actually show Milliseconds but the lowest I could get to was 0.08 seconds! Still thousands of times slower!)
While this level of latency is a target, and an achievable one, it does rely on perfect conditions and perfect compatibility between both devices. In reality, latency as high as 50 - 70ms will be generally unnoticeable too.
In fact, a "good latency" very much depends on the technology being used. For example many videogames will stop players connecting with latency above 100ms, while 33ms is required for perfect frame-matched viewing of TV with wireless headphones.
If your wireless devices don't have a video component (for example playing music on your car stereo via Bluetooth) then latency is a whole lot less important, because the music and video can't desynchronise. In these cases latency can be in the hundreds of milliseconds with very little affect beyond a delayed pause or volume control input.
General Latency Checklist
1. Does your connection need video and audio to be synchronised?
Yes -33ms latency ensures perfect sync at 30fps. 16ms ensures perfect sync at 60fps.
No -Move on to Question 2
2. Does your connection need frequent interaction?
Yes -Below 60ms is advisable for snappy controls and dynamic interactions
No -Any strong wireless connection will suffice
Bear in mind that "Perfect sync" is not really required for most viewing, even with video components. You will only begin to actively observe and notice lip de-sync and other anomalies when latency is very far from the target. For example, 40ms of latency is generally plenty for watching TV, despite the exact sync being closer to 33ms.
What Does "Low Latency" Mean?
Finally, beyond simple millisecond measurements, there are technologies which aim to provide "low latency" connections. When this term is used in general parlance it simply means "Below 60ms-ish" but in certain contexts the term has a more specific meaning.
The company Qualcomm have made Bluetooth enhancements for years and one of these was "aptX Low Latency". In this context, "Low Latency" was a specific technology which lowered response times in Bluetooth devices to 40ms. Back then, Bluetooth couldn't reach that low without this.
Nowadays, Bluetooth 5.0 already reaches latencies below 40ms and so the "Low Latency" enhancement became redundant. The term returned to a more general use, explaining any wireless device that communicated quickly.
For this reason, it's best to ignore the term "low latency" and look for an actual Bluetooth version or Millisecond measurement, to be absolutely sure of a product's latency.
Buy Adapters and Devices With Confidence
Having a grip on latency can help you buy the products you need for your usage. For example a pair of headphones for the kids in the back of a car don't need to be equipped to receive anything lower than the standard 50 - 80ms range as they will just have music from the car stereo left on, so won't be needing any instant controls or video sync.
If you are looking into a Bluetooth adapter for your TV, though, you'll need to check it can support latency as low as 40ms to ensure smooth synchronisation between video and audio.
