[linux-audio-user] Re: Firewire, what's the story?

Clemens Ladisch clemens at ladisch.de
Tue Dec 9 03:25:42 EST 2003


Mark Knecht wrote:
> On Mon, 2003-12-08 at 16:29, Jack O'Quin wrote:
> > Steve Harris <S.W.Harris at ecs.soton.ac.uk> writes:
> >
> > > Latency shouldn't be an issue - the 1394 bus is low latency - higher
> > > latency than PCI I expect, but still not measurable in audio terms.
> >
> > Does it have the same problem as USB, using fixed-time rather than
> > fixed-size packets?

Yes.

> > I seem to recall that it does, but that the packet size is smaller,
> > making the latency problem easier to deal with.
>
> Isoch - 1394 has a timer operating on the bus. This timer happens
> (roughly) every 125uS.

USB isochronous transfers happen once per millisecond.


Regards,
Clemens




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