11 Nov
2009
11 Nov
'09
6:30 p.m.
Giso Grimm:
Maybe I am something missing, but what about the clock
synchronisation?
There are works to make ieee1588 (PTP) into linux, [1-4].
That might help.
In [5], they seem to get <10us offset from a master within 2minutes
converging time. [6] gives a little different picture.
It would be nice to allow synchronisation of several
devices via the
network connection. This transport medium typically has a lot of jitter
(even an unloaded gigabit system can be above 50µsec), however, the
jitter of typical AD/DA converters should be in the order of
nanoseconds.
Do you (or anyone else) know the maximum allowable jitter useful for
audio?
And in the case of several devices, how is it possible
to
compensate the absolute delay? All devices should be in phase, with a
deterministic inter-device delay.
We have to think about that, I have no answer today.
If it is only a single device it should be possible to
use netjack: Then
it behaves as a small host with its own sound card, and running jack
with netjack_client (or whatever it ins called in recent versions). Any
remote PC can run jack with the net backend to connect. Well, with
netjack for jack0.116.2 the connection request is made from the other
direction, in this case the open sound card, but connect requests could
be triggered via OSC. And Netjack2 for jack2 seems to work completely
differently.
So, it amount to write an alsa driver then?
Regards,
/Karl
[1] http://www.ixxat.com/evaluation-kit-linux-live-cd_en,24073,5873.html
[2] http://ptpd.sourceforge.net/
[3]
http://www.estamos.de/blog/2009/07/01/linux-2-6-30-hardware-assisted-time-s…
[4] http://bombadil.infradead.org/pipermail/ptpd/2009-November/000012.html
[5] http://ptpd.sourceforge.net/ptpd_2005_1588_conference_paper.pdf
[6] http://www.linuxclustersinstitute.org/conferences/archive/2008/PDF/Ohly_922…
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Lilla Aspö 148 Networks
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