[PD] hid object and latency

Hans-Christoph Steiner hans at eds.org
Wed Oct 10 19:08:13 CEST 2007

USB HIDs are usually polled every 8ms to 10ms, which is plenty fast  
(have you ever noticed the latency of your mouse pointer or  
clicks?).  I have not seen any reports of latency caused by [hid],  
but I suppose it could be possible.


On Oct 7, 2007, at 8:30 PM, Warrior Bob wrote:

> Hi list,
> First off, I'm new to pd but it seems to be a fantastic environment.
> Big thanks to everyone who's worked on it.
> I've run into a problem.  I built a pd patch to translate joystick
> button inputs into MIDI note signals using hid and noteout.  Indeed
> it functions correctly, and there are no logic errors that I can find
> as far as which button triggers which note.  However there is
> noticeable latency, too much to use to play an instrument in realtime.
> Using a MIDI keyboard to send the same notes (bypassing pd), I
> encounter no latency that I am able to discern easily.  I believe the
> latency must be related to pd, either in my patch or in the hid
> object, or in my joystick's USB interface (a playstation to USB
> converter).  Is this a known issue in pd or hid, or has anyone
> encountered this before?
> If it helps, I am running on a G4 Macintosh, using pd .38.4 extended,
> and using the IAC Driver to get MIDI data between programs.   I have
> hid polling at 1ms intervals, and am using the Ableton Live demo as
> my destination (triggering the Impulse plugin).
> I am almost totally convinced that the latency is in the USB
> interface, and therefore there is nothing I can do, but I figured it
> was worth asking.  I spent a while going through the list archives,
> Google, and the documentation but did not find anything.
> Thanks in advance!
> Dave H.
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Computer science is no more related to the computer than astronomy is  
related to the telescope.      -Edsger Dykstra

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