04-08-2020, 10:26 AM
Hello everyone. I'd like to ask a question about jitter. I connect the control unit of my Roland electronic drums to the computer with Behringer UMC202HD USB interface. The latency value is approximately 4 ms and is OK but the Jitter input and Jitter output values fluctuate continuously. They almost always remain on the green but sometimes, for a moment, they exceed 0.50 ms and turn yellow. I haven't figured out if this can only affect sound quality or even latency. In addition, I would like to know how I can make the Jitter stable and keep it constantly on the green. Thanks.
Getting a little more technical: jitter is the VARIATION in the latency you experience, from roughly 1 second to the next. Using the numbers stated above, you would describe your latency as "4ms, plus or minus about a half-millisecond" What causes the latency to vary like that? Well, understand that your audio information is broken up into packets of data that travel thru your computer interface and computer software & hardware, (and during a jam session) over the Internet to others. These packets travel over shared electrical "highways" that carry other packets as well. At any given instant in time, there may be congestion - some packets may "hit more traffic traveling" than the other packets, just because other things are going on at the same time. Should you worry if it's yellow or red? In my experience the yellow coloring occurs when the jitter is above about 10% of the measured latency. And that pretty much is what you are seeing, as 0.5ms is about 10% of 4ms. Red is when the jitter is more than 25%, or above 1 whole millisecond for a 4ms latency. A difference in time delay of even a whole millisecond is almost unnoticeable to the ear, however, and therefore as long as your reported latency is a low value like 4ms, you should be fine as long as the jitter doesn't go crazy (I have seen jitter values in the hundreds of milliseconds, but that indicated a software problem). Where jitter DOES start to matter is the COMBINED latency & jitter of all players. Someone you're jamming with may have a gear latency of 10ms+/- 3ms jitter, and you may have an Internet latency of 13ms+/- 6ms jitter. The result would be a jam session of 27ms of end-to-end latency, varying by as much as 10ms. This will feel like sloppy playing, and everyone struggling to stay on the beat.
So think of them as 2 different performance values: Latency is the (more or less) fixed time delay between players. The combined jitter is that rapid fluctuation in time delay, which feels like players with bad senses of timing. Your brain can tolerate each to different amounts.
Hope this helps
