Latency is one of the most important aspects of online music performance, and also perhaps the least understood. We are writing a series of blog posts to shed more light on the concept and nuances of latency. We’ll start in this post with a primer on how latency works in both in-person and online music performance environments.
As it relates to online music performance, latency is the time it takes for the music played by one musician to reach the ears of another musician in a session. If there is too much latency in a session, musicians will have trouble playing in sync with each other.
We are often asked, “does JamKazam have no latency?”. The answer to this question is no. Latency exists in in all music performance environments, including in-person performance. Here’s a relatively simple way to think about and understand latency (warning, a bit of math incoming).
Latency in the Physical World
The speed of sound is about 1 foot per millisecond. A millisecond is one thousandth of one second. If two musicians are playing music in the same room 15 feet away from each other, there will be 15 milliseconds of latency in their live performance. This is both typical and quite tolerable. Now let’s consider a marching band on a football field. Let’s say the band is spread out from one 20-yard line to the other. That’s 60 yards = 180 feet, and that translates to 180 milliseconds of latency between musicians on the far ends of the band. This is far too high to play in sync together by ear, which is why marching bands need drum majors to supply a visual signal of the tempo to keep the band playing in sync over these distances.
Latency in the Digital World
While the speed of sound is about 1 foot per millisecond, digital sound can move across the Internet closer to the speed of light at about 100 miles per millisecond. For those inclined to understand the details of this estimate/calculation, there is a paragraph at the end of this article. If we were to ignore other sources of latency and consider only Internet latency, this means that two musicians who are 1,500 miles apart would experience the same latency in an online session as two musicians sitting 15 feet apart in a room together – i.e. 15 milliseconds in both cases. However, there are two other sources of latency in online sessions – audio processing latency and jitter-driven latency. These are explained in our Part 2 blog post on the subject of latency: Sources of Latency in Online Music Performance.
Curious To See How This Works?
While we understand the natural skepticism many musicians feel about the ability to play together live in sync in online sessions, we’d point out that musicians have now played in more than 3 million online sessions on JamKazam. You can check out a small handful of sample performances in this YouTube video, with all the musicians playing on JamKazam from their homes over the Internet. If you’re interested in trying it out, you can do so risk-free by going to https://www.jamkazam.com and signing up for a free account. We have a support team that can help you get set up and playing online successfully in private sessions with your band or in open/public sessions with other musicians if you’re not in a band.
Estimating the Speed of Digital Sound Across the Internet
As promised above, here’s some data/math behind music/audio in the digital world. We’ll start with a caveat that this is in imprecise estimate by its nature, but here goes… The speed of light in a vacuum is about 299,792,458 meters per second (m/s), but light travels slower in fiber optic cables due to the refractive index of the glass, which typically ranges from 1.44 to 1.5. So an Internet packet can travel about 125 miles in 1 millisecond through a fiber optic cable. However, network latency includes other factors like switching, routing, and processing delays, which reduce the effective speed, as well as last mile connectivity in some cases through cable connections. As a result, we lower the estimated speed to about 100 miles in 1 millisecond.