[sdiy] Bunching of MIDI clock messages

René Schmitz uzs159 at uni-bonn.de
Wed Sep 11 14:28:25 CEST 2013

Jörg Schmitz has analysed the timing of some software sequencers
some years ago:

The trouble seems to be the time-slices of the OS, as can be seen from 
the distributions.


Am 11.09.2013 13:32, schrieb rburnett at richieburnett.co.uk:
> How common is "bunching up" of MIDI clock messages due to erratic
> transmission out of sequencers?
> For example, if I check for the reception of a MIDI clock message every
> 2 millisconds in a receiving instrument is that sufficient?  (In theory
> 2ms polling rate should be sufficient to support tempo up to 1250 BPM
> provided the clock events arrive with even spacing!)  Or do you think I
> should cater for the possibility of receiving as many as seven MIDI
> clock events transmitted "nut to butt" over my 2 millisecond polling
> period!?!?
> I know the MIDI specifications says that MIDI clock messages are to be
> transmitted with even spacing at the average tempo rate, but I don't
> think i've ever seen a maximum jitter specification anywhere?  (I can
> just imagine sequencer software getting preempted in a Windows
> environment, and later transmitting all of the overdue MIDI data in an
> intense burst.)
> Any thoughts/experience on this?
> Cheers,
> -Richie,
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uzs159 at uni-bonn.de

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