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

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Subject: Re: [linux-audio-dev] a question re: the MIDI spec
From: Steve Harris (S.W.Harris_AT_ecs.soton.ac.uk)
Date: Sat Sep 11 2004 - 12:43:16 EEST


On Fri, Sep 10, 2004 at 10:40:05PM +0100, Martijn Sipkema wrote:
> [...]
> > > > > 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.

- Steve


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