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

Torben!

>> 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. 

You mean in the case where jack would only operate on AVB streams and
not use any local sound interface?

I was thinking of the case where jack operates on a local backend and
does SRC on AVB ports, if neccessary.

>> 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.

It is not I who wants it, it is the spec that demand a phase synchronous
clock that matches AES criteria, and bit transparency, amongst other things.

> but to just output a stream.... no special hardware is needed.

If you just produce sound (and do not care about synchronization with
other sound sources) or want to store the data, yes. In any other case
you need a means of hardware synchronization.

> clock extraction out of streams becomes harder with higher jitter.
> so with an exact ptp clock, things are dead easy.

Just a bit of housekeeping.


Flo
-- 
Machines can do the work, so people have time to think.
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