[linux-audio-dev] a question re: the MIDI spec

[Martijn Sipkema]

> > [...]
> > > > > > The problem here is that class compliant devices suffer bad timing
> > > > > > because they use bulk transfers for MIDI data. The standard for
> > > > > > MIDI over FireWire is much better.
> > [...]
> > > > > Is the timing really that bad?  I don't even think a firewire 8x8
> > > > > rackmount MIDI interface exists, so my options are kinda limited. :/
> > > >
> > > > Timing is especially bad when there is other data being transferred on
> > > 
> > > "Especially bad" is still pretty vague. What might look bad on paper might be 
> > > acceptable in context... 
> > 
> > It's not unusable, but IIRC it can get to several ms of jitter.
> 
> Why is that? The USB iso clock is every ms IIRC, so naively you
> would expect the maximum jitter to be just under 1ms (if the bus was
> saturated by audio transfers), and less in proportion to the degree of
> saturation.

Yes, one would expect that (if there are no other bulk transfers), but
somehow this does not seem to be the case:

http://www-2.cs.cmu.edu/~eli/papers/icmc01-midiwave.pdf

--ms