[alsa-devel] Control the exact moment of output

Rob Janssen pe1chl at amsat.org
Wed Apr 30 10:11:28 CEST 2014

Patrick Shirkey wrote:
> Have you looked into netjack?
> Several of the network timing issues have been worked through quite
> extensively. We have used it to distribute data across several machines in
> a cluster and find it to be very stable and workable with acceptable
> latency over gigbit lan.
> You might find netjack gives you a good headstart on this project.
> Adding support for JACK is a minor task compared to rewriting (and
> testing) netjack.  You will also gain access to a host of other
> professional functionality and ALSA, OSS, FIrewire support too.
> In addition your software will play nice with other professional software
> and have direct access to data on the JACK graph as a bonus.

Thanks for the pointer!  It indeed appears that this project is trying the same thing as
we are doing.

It will require some further study.  Documentation appears to be scarce, I have not been
able to locate a document yet that describles what it actually achieves and what caveats
there are.  I saw one thing on the Wiki: it transmits data all the time.  We will probably need
some form of on/off control to avoid wasting bandwidth, but maybe it can be done in a CODEC.

I also saw it has fixed network latency setting, while I had already envisioned a system for
automatically determining the added latency based on feedback from the remotes.

But at least it provides a lot of insight into using Alsa in timing critical applications, something
I had been looking for.

(I know that writing documentation is a drag, but projects like Alsa and this one would be so
much more useful and accessible when there would be more detailed documentation that
goes beyond an installation HOWTO and a plain listing of available functions and parameters)


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