Sampling rate for physical controllers

Feb 28, 2008 at 2:48pm

Sampling rate for physical controllers

Hi,

I’m looking for some information and references on appropriate sampling rates for physical controllers, specifically control surfaces with knobs and faders and so on. Personally I find that around 10-25ms sampling period seems to work fine, but I wonder are there any good studies or definitive results? I want to record incoming control data in Max accurately, but efficiently. Really my question is: how fast or at what frequency can someone typically move a knob or fader? or is it usually limited by the hardware in generally available controllers?

Thanks,

Aengus.

#36100
Mar 1, 2008 at 7:58am

aengus schrieb:
> Really my question is: how fast or at what frequency can someone
> typically move a knob or fader? or is it usually limited by the
> hardware in generally available controllers?

Generally available controlers is not very specific. If its Midi, its
event driven, the highest rate is the speed Midi can send data (ca. 1 ms
per command) I prefer that approach over any “Sampling rate” sometimes
called polling. A sample rate of 10-25 ms might be fine, but is always
too slow for catching rythmic events. I need the event in the moment it
happens. 1 ms is fine for that. If you do it with polling/sample rate,
you’d need a sample rate of 1 kHz which produces most of the time
unneeded data and locks your machine for no advantage…

Stefan


Stefan Tiedje————x——-
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#123617
Mar 4, 2008 at 11:52am

I understand that rhythmic events require much higher sample rates, but I’m thinking of an automation-type application -recording and playback of some continuous parameter value such as a level or the centre frequency of a filter- I can only think of ways of doing that in Max which involve metro-driven polling of a value. Also in my case, I want to process the control data and my processing requires that the data are recorded at a fixed sample rate.

Is there a definitive minimum for that sample rate? Or even a generally accepted range?

Thanks,

Aengus.

#123618
Mar 4, 2008 at 6:06pm

On Mar 4, 2008, at 3:52 AM, aengus wrote:

> Is there a definitive minimum for that sample rate? Or even a
> generally accepted range?

For knobish things, I’ve found that a 25-50 ms polling rate, with
(optionally) interpolation between points on playback, is a pretty
good compromise between maintaining gestural accuracy and data
reduction.

The Gesture Recorder stuff I put up on my site does that:

http://www.xfade.com/max

Chris Muir
cbm@well.com

#123619
Mar 4, 2008 at 10:58pm

There isn’t really a fixed “standard” when it comes to control latency.
If you talk to most musicians, they will want “as little as possible”,
but you are going to be limited by the speed of whatever hardware
communication protocol you use. Pretty much any hardware interface is
going to have some amount of latency, but it will vary with the
particular implementation. You will have to find your own happy balance
between data-rate, processing speed, hardware limitations, and
perceptual effectiveness. Most people I talk to find that up to 50ms is
musically tolerable, and sometimes more if temporal interpolation is
used effectively. I would probably try to keep it below 50ms if possible.

Andrew B.

#123620
Mar 4, 2008 at 11:50pm

Andrew Benson schrieb:
> Most people I talk to find that up to 50ms is musically tolerable,
> and sometimes more if temporal interpolation is used effectively. I
> would probably try to keep it below 50ms if possible.

Yes, if its a constant latency, no if its jittery (f.e. varies between 0
and 50 ms) – polling creates jitter. Midi is fine, fast and could be
thinned without loosing that precision with speedlim for example…

Stefan


Stefan Tiedje————x——-
–_____———–|————–
–(_|_ —-|—–|—–()——-
– _|_)—-|—–()————–
———-()——–www.ccmix.com

#123621

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