[sdiy] Bunching of MIDI clock messages

[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,