Better Latent Than Never
A long overdue discussion of audio latency issues

By JD Mars



The question of "what's the latency?" has a double meaning. When you ask, "what's the latency" of an audio card, you have to ask what latency it is that you speak of, forcing you to define "what's the latency?"

Breaking out of this Mobius Strip of questions, what is latency and what are the issues that surround it? There are essentially four instances where latency comes into play in the realm of digital audio devices and hard disk recording, with divergent ramifications.

ASIO Latency

ASIO is a standard for audio device drivers created by Steinberg. As much as possible, ASIO bypasses the Windows or Mac operating system, creating a more efficient communication between the audio device and the software. Currently, all of the Steinberg programs use ASIO (of course), while other programs (including software synthesizers) have also adapted the standard. The question, "what's the latency" in this instance is only relevant if the program is ASIO-compliant and if the audio card's device drivers also contain ASIO drivers.

Then, this question will need to be answered by the sound card company. Different sound cards will have different latencies at different sampling rates -- the higher the sampling rate, the lower the latency. In that sense, the latency occurs in numbers of samples, dependent on the number of samples that need to be put into a buffer before monitoring begins. Because the latency in samples is fixed or defined by the card, then the faster the sampling rate, the quicker a fixed number of samples will pass through the buffer. Hence, faster sampling rates = lower latencies. Often, a buffer size can be set in the sound card's control panel, and a lower buffer size = fewer samples that need to be buffered. As long as your system can handle the lower buffer size, lowest is best.

The latency in this case comes into play when we are monitoring in a "tape type" fashion, which is essentially monitoring through the program. We'll discuss Windows latency later in this article, which also affects the user while monitoring, but only with the efficiency of ASIO are we able to achieve this type of monitoring. It goes something like this: While I have the program in 'input,' I hear my instrument from the inputs of the program much like a pro tape deck. If I 'roll tape,' or rather put the program into play, I no longer hear the instrument until I punch in, again like a pro tape deck. All of this, unlike a pro tape deck, occurs with a bit of latency between what you're playing and what you're hearing through the program.

Steinberg says that 11 or 12 milliseconds of latency is acceptable. You can be the judge. At higher sampling rates, 3 ms latency might be possible. If you desire this type of monitoring, which is a fairly normal and accepted way of recording, then this may be the best that hard disk recording has to offer.

The EASI and MAS Standard

Emagic and MOTU have created a standard of their own, similar in nature to ASIO. Right now, only the latest, higher version of Logic Audio utilizes EASI, as is the case with MOTU's MAS standard. The same 'tape type' monitoring' is possible with EASI or MAS compliant device drivers.

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