[LAU] Value of low-latency in audio?

[Brent Busby]

On Fri, 11 Dec 2009, david wrote:

> Just wondering. Without an RT kernel here, my 2 laptops seem to run my 
> simple audio needs pretty well at 64msec latency. At least, it's never 
> bothered my playing along with computer-generated audio.

If your recording card can provide its own monitoring (M-Audio Delta and 
RME Hammerfall family both can), then for most things, your Jack latency 
doesn't seem to even matter.  I keep mine set to 21ms 99% of the time I 
use Jack, even though my system is very fast and stable, and is capable 
of running at *2ms* all day without xruns.  When the recording card is 
providing your monitoring, you basically have *zero* latency regardless 
of how your Jack settings are configured, and then it doesn't matter, 
because then you're in the wonderful world of hardware.  :)

Where it does start to matter is when you start using software-based 
sound sources, like LinuxSampler, or virtual synths.  Your recording 
card's monitoring can't help you much with that, and then you just need 
good enough latency to not end up feeling like you're hearing the output 
of what you're playing only after it's gone through a tape delay. 
Probably anything under 10ms is decent, but if you don't have some awful 
USB-based interface (which are a recipe for latency hell usually), you 
can probably do a lot better than even that.

> I see people on the list running much lower latencies than 64msec, and
> seemingly trying to get even lower ...

It does seem to be almost a competition sometimes...  Seriously, as some 
other people have pointed out once on here, you get a certain amount of 
natural latency in the acoustic world just from having a jazz group 
performing on a stage with some space between the players, since sound 
does take some time to travel, and the human ear can perceive *really* 
small timing differences in sound arrival timing as stereo position, 
distance, direction, and all that.  It still doesn't keep anyone from 
playing music on a stage though!  Any Jack latency under 10ms is really 
good.  I keep mine at 21ms when I'm working entirely with hardware 
monitoring and hardware musical instruments and effects (which is most 
of the time).  The Hammerfall/Multiface has its own hardware-based 
zero-latency monitoring and makes it not matter at all in that 
circumstance.

-- 
+ Brent A. Busby	 + "We've all heard that a million monkeys
+ UNIX Systems Admin	 +  banging on a million typewriters will
+ University of Chicago	 +  eventually reproduce the entire works of
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+ James Franck Institute +  we know this is not true." -Robert Wilensky