[Ardour-Users] Enough Already was Sync between internal and external sources

[Arnold Krille]

On Thursday 22 January 2009 22:06:31 Mark Greenwood wrote:
> Some time ago there was a comment on this thread that made a point I
> found particularly interesting. It referred to latency in the hardware
> itself. I'm using a Firewire Edirol FA-66. Might there be some extra
> latency in the firewire interface? I agree with others who say 5ms
> should be musically irrelevant, but there is definitely a latency in my
> system that I can hear. Might firewire latency explain it? And if so,
> can it be compensated for, or lessened?

The latency introduced by firewire (or by usb) is indeed bigger then only the 
latency introduced by pci and the device itself with its converters and 
buffers. But when jack reports 5ms latency on freebob, the real latency 
shouldn't be more then 10ms in total.

> I've done some messing around and updated my version of Jack and started
> using FFADO instead of the Freebob I was using.. QJackCtrl now reports
> my latency as a fairly astonishing 2 ms. That of course is (only) the
> software latency, or so I believe. I will continue to experiment.

FFADO compensates the latency of pci(?) and firewire-protocol. So the only 
latency you have to add there is the latency of the device itself with its 
converters and small buffers.

Btw: My experience from telling professional musicians and technicians about 
linux audio (at LinuxTag) was raised eyebrows and "wow" to my "latency? 5ms on 
low grade consumer hardware."
When they talk about zero latency they mostly mean "hopefully less than 
20ms"...

Have fun,

Arnold
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