[PD-ot] how low (latency) can you go?
Bryan Jurish
moocow at ling.uni-potsdam.de
Sat Dec 16 22:52:54 CET 2006
On 2006-12-16 20:44:22, Hans-Christoph Steiner <hans at eds.org> appears to
have written:
>
> On Dec 16, 2006, at 1:14 PM, Bryan Jurish wrote:
>
>>
>> On 2006-12-16 19:02:08, Hans-Christoph Steiner <hans at eds.org> appears
>> to have written:
>>> And always, when talking about latency, I feel the need to point out
>>> the speed of sound: 340 m/s or .34 m/ms. So if your speakers are 2m
>>> away from you, that's 6ms of latency. You could spend days tweaking
>>> your machine to get 3ms less latency, or you could move 1m closer to
>>> your speakers. Puts things into perspective...
>>
>> indeed 'tis true. but 5ms vs. 10ms makes a major
>> subjective/perceptual difference if we're talking about playing an
>> electro-acoustic instrument in and getting a munged signal out...
>
> Do you have any references on that? I think it could be perseptable to
> a very experienced musician, but I don't think there is a major effect.
well, i wouldn't call myself a *very* experienced musician, but plugging
a guitar into the computer and just running the signal through a simple
[adc~]->[dac~] in pd with 10ms reported latency (latency.pd gives
10-11ms) is easily detectable, it being a pain in the wazoo to play
(probably has to do with the fact that i am at best only a mediocre
guitarist, but that's not the point :-/). also, 10ms is roughly the
minimal "willed action -> muscular implementation" latency on your
average homo sapiens architecture (get a stopwatch, try it out ;-)
> From the studies that I have read, jitter has a much larger affect
> than latency in terms of affecting performance. (I need to find
> some references myself... ;)
i think you're right there. i know Reinhold Kliegl and Ralf-Thomas
Krampe have done a lot of rhythm perception studies in Potsdam, with
professional musicians, amateur musicians, and non-musicians as
subjects, and the pros pretty much blew everyone else away precision-wise.
> Performers are actually quite adept at adjusting to latency. Just
> think of an orchestra or choir: there could be 20ms or more of
> latency from one side of the stage to the other, yet its not hard
for > a moderately trained group to handle it.
as a former orchestra inmate myself, i seem to recall concentrating
mostly on keeping a constant time myself -- the "big picture" ("big
sound?") just isn't available to a 3rd tier 2nd violinist -- i went by
the conductor's tempo and the momentum i got from those around me: the
only real trick was keeping it constant, but that's "just" training:
hence perhaps the jitter-related problems even for the pros...
> Another key factor in performance is
> physical feedback, which has a much faster feedback loop that the audio
> system. Trained musicians can feel a mistake and correct it long before
> the sounds are consciously perceived. (I first saw that in print on one
> of Miller's papers http://crca.ucsd.edu/~msp/Publications/icmc93.ps)
>
> One realm were I could see that latency would be important would be when
> measuring response time to a stimulus, like in a psychological
> experiment. But even still, as long as the latency is steady (i.e. low
> jitter), the latency is not a big deal.
it can certainly be compensated for if it is known, but for me as a
guitarist, it amounts essentially to learning an entirely new style,
since i'm just plain not good enough to compensate before the glitches
become painfully audible...
marmosets,
Bryan
--
Bryan Jurish "There is *always* one more bug."
jurish at ling.uni-potsdam.de -Lubarsky's Law of Cybernetic Entomology
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