[LAD] [LAU] Open Source Audio Interface

Fons Adriaensen fons at linuxaudio.org
Thu Sep 11 21:17:26 UTC 2014

On Thu, Sep 11, 2014 at 09:10:36AM -0700, Len Ovens wrote:

> On Wed, 10 Sep 2014, Fons Adriaensen wrote:
> >On Tue, Sep 09, 2014 at 03:57:06PM -0700, Len Ovens wrote:
> >
> >>I thought I would move this over here. I know there is already work
> >>being done on this hw wise. These thoughts are for a point to point
> >>raw ethernet audio transport That still allows some normal network
> >>traffic as well.
> >
> >Zita-njbridge will do this, point to point or one to many.
> >
> >Each system can have its own sample rate and period size,
> >no word clock sync is assumed.
> Yes, this project would not replace that functionality.

If any audio HW would transmit the packet format expected by
zita-n2j (which is fairly simple), it would just work. You 
could even have many such interfaces connected at the same
time (all it takes is a network switch) and they wouldn't
need a common clock.

And of course it is possible to create a Jack backend that
accepts the same format but without the resampling (that's
in the pipeline actually).

Re. the format used by njbridge: for IPv4 the IP and UDP 
headers together take 28 bytes. That is less than 2 percent
of 1500, and is a small price for having packets that can be
handled by switches and routers. There is really no point in
trying to reduce that sort of overhead. The njbridge format
itself adds a 20 byte header to sample packets. This data is
used to identify the packet, to improve the timing and handle
skipped cycles, xruns, lost packets and the like. All together
the overhead is less than 3.5%.



A world of exhaustive, reliable metadata would be an utopia.
It's also a pipe-dream, founded on self-delusion, nerd hubris
and hysterically inflated market opportunities. (Cory Doctorow)

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