Re: [Jack-Devel] Jack-Devel Digest, Vol 56, Issue 47

On Sat, Feb 26, 2011 at 09:29:55PM +0100, Florian Faber wrote:
> On 02/26/2011 09:16 PM, Arnold Krille wrote:
> 
> > But afaik git has the advantage that one can move whole development branches 
> > including history from one server to the other. So we could also start on 
> > github or something and get it completely included in a more mainline jack-
> > repository without loosing historic commits like "it works!" or "Initial 
> > commit"...
> 
> I believe you guys see it with from the wrong perspective. I don't see
> AVB support in jack as a backend, but as a simple bridge from AVB ports
> to jack ports.  This can be achieved by simple stand-alone tools, much
> like netjack.

netjack also has a backend.
if you want to slave jack to some external clock, you need to write a
backend. 

so for the case where you want to slave jack to some avb devices,
you need to write a backend.
this use-case is particularly interesting, because it will work with
normal hardware. (it probably doesnt even need a software ptp
implementation)

> 
> If you want to provide physical inputs or outputs for Ravenna on your
> machine, there's nothing you can do without special hardware - for the
> moment. You have to produce a phase synchronous clock, synced via PtP,
> and provide a means to timestamp incoming samples and output samples at
> the correct point in time.

this doesnt seem to be true.
sure... if you want different output device clocks to be correlated,
then you need an accurate ptp clock.

but to just output a stream.... no special hardware is needed.
clock extraction out of streams becomes harder with higher jitter.
so with an exact ptp clock, things are dead easy.

netjack1 is pretty good with extracting a clock from a WAN stream.


-- 
torben Hohn

1298818326.11029_0.ltw:2,a <20110227145137.GB2977 at siel dot b>