[sdiy] Bunching of MIDI clock messages
tom at electricdruid.net
Wed Sep 11 21:23:36 CEST 2013
That's how I did it. Seemed reasonable to me. I would imagine other people have had the same idea as us both. I have to admit that partly my motivation was to avoid repetitive MIDI clock and other real-time data clogging up the MIDI input buffer, rather than any high-minded sense of timing accuracy!
On 11 Sep 2013, at 13:39, ChristianH <chris at chrismusic.de> wrote:
> Wouldn't it be more reasonable to immediately increment some internal
> time code counter right from the MIDI reception interrupt handler,
> rather than checking for it at some other time after passing through a
> FIFO? Isn't that what real-time messages are about?
> Ok, probably some locking mechanism will be needed to prevent
> concurrency issues.
> On Wed, 11 Sep 2013 12:32:31 +0100 rburnett at richieburnett.co.uk wrote:
>> 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
>> 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?
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