Re: Sooperlooper or Mobius? Going back to software.

[Jeffrey Larson <jeff@zonemobius.com>]

 > The difference in latency between the Presonus Firepod (8 channel)  
and
 > the RME800 was huge.  The latency with the Firepod was in the  
order of
 > 350ms.

It is a common misconception that audio interfaces "have latency" and  
that
one will be faster than another.  Audio interfaces all have a very
small amount of analog/digital conversion latency and they are all
about the same.

What we think of as latency is actually something we have to tune to
account for the all the crap that can happen moving the samples from
the A/D converter to the audio application.  This is affected by lots
of things including the device driver software, CPU speed, amount of
RAM (virtual memory paging), network adapters demanding attention,
video cards demanding attention, and all the hidden system processes
that are running at the same time.

Badly written device drivers can cause delays that require higher
latency to avoid clicks and pops.  Since most people don't think
of the hardware and the device driver as different things a certain
device can be branded as having "high latency" which may actually
be fixed later by a driver update.  Always make sure you have the
latest drivers.

 > There were some other problems too (my video chipset and the
 > Firepod's chipset didn't peacefully co-exist on the PCI bus -- this
 > could have caused bandwidth/latency issues, too.)

I think you've nailed it.  Video chips/cards are a common source of
contention that can cause delays which require larger buffer sizes to
avoid clicks.  I don't doubt that swapping the PCI interface for a
Firewire interface solved this problem, but so too could have swapping
the video interface for a higher-end card with dedicated memory.

The RME is a very fine device and they seem to be very good at
writing device drivers.  But we can't make blanket statements
like "the RME has lower latency than the Firebox".  It worked
for you, but there may be no difference on another machine.

Jeff