Decrease latency through the Helix Board/Firefly
Posted by Rick Shao on 16 November 2015 08:06 AM
So what is latency? In essence, latency simply means 'delay'. So, in our instance, it refers to the delay in audio that exists between two devices (eg. the Helix Board and the computer). But why does it exist? Well, as most computers do not offer real-time operating systems - meaning they do not always perform all processes immediately upon request - on occasion the computer won't record/receive audio as fast as it should.
The end result is pops, clicks, lags and glitches in the audio. To compensate for this, the Phonic Control Panel (like many other manufacturers) offers a 'buffer' function. This allows the computer to take samples of the audio, place them in memory (RAM - Random Access Memory) until it's ready to be processed. Once one sample is taken from the RAM and processed, another takes its place within the RAM.
So it's important to remember that, while it is possible to get zero audible latency, the idea of there being absolutely no latency between your mixer and computer is just a pipe-dream. You can, however, minimize it so that you'll never even know it's there.
The first thing you can do is check out our article "Optimizing a PC for use with the Helix Board or Firefly digital interface". Here we discuss the various ways you can help improve your system's performance. The smoother your computer runs, the less chance there is of the pops, clicks, etc, and the lower you can set your buffer settings.
A buffer setting of about 512 samples per second (or lower) should give you perfectly acceptable results. This is really what you need to aim for, but sometimes - depending on your computers performance - it may be unobtainable.
There are a couple of other ways to combat latency, however.
First off, you can try using hardware monitoring. Monitoring the recorded signal may give you an idea of how your recording is going, but at the end of the day if your levels are set correctly where is the harm in monitoring directly from the mixer itself?
You can also try changing the sampling rate. If you were to double the sampling rate used and go from, say, 48 kHz up to 96 kHz, your latency will be cut in half. Why? Because the samples are twice as large, therefore you'll be using up the buffer twice as fast.
All the above tricks should help lower your latency, and hopefully reduce the possibility of pops, clicks and such. It's important to remember that, while your computer may be a high-end system, it doesn't necessarily mean there isn't something that will cause the problems described in this article. Follow the steps described and hopefully you'll see some real improvement.