Re: [LAU] netjack and WiFi

On Sat, Jan 09, 2010 at 02:30:35PM -0500, Michal Seta wrote:
> Hi all,
>
> Happy new decade!
>
> Back on that WiFi jamming issue I wrote about a while ago. Thank you
> all for the various suggestions. I have spent most of my time trying
> to get somewhere with netjack as I found it the most promising, not
> only in terms of efficiency but also scripting and control. However,
> I have hit some brick walls which are certainly due to the nature of
> WiFi networks (packet collisions and such) which make my setup very
> unstable.
>
> First of all, in my setup, there will be one "server" computer
> collecting 5 signals from the 5 musicians and playing them for the
> audience. Moreover, the operator (or software) will send back 5 mono
> signals to performers (one signal per performer). The idea is that
> each performer hears only one instrument at a time.
>
> Currently the show stopper lies in alsa_in and alsa_out components.
> Whenever I run both on my netbook (Atom 1.6G with Atheros
> Communications Inc. AR5001 Wireless Network Adapter (802.11g)) they
> consume around 70-80%CPU and they peak at around 50% each whenever
> they choke on net over/underruns. They eventually segfault (and
> sometimes bring the jack server down with them. This particularly
> true whenever the WiFi signal signal strength is weak (around 50-60%).

you might want to use -q0 to reduce the quality of the resampler.
however they will give you CPU spikes, with the current packet loss
algorithm. because jack will run pretty fast, when it catches up after
a period of sync loss.

i am sorry that its not working so good currently.
while trying to fix a different bug, i changed the packet loss
behaviour, and its pretty useless for your case now.

> I was especially surprised at the high CPU consumption of those apps,
> as I figured that if all they do is schlep audio to and from the
> soundcard they would keep a low profile... My built-in audio
> interface is:

no. they resample the audio they transfer. and libsrc can be quite heavy
in high quality mode.

> It is an Acer Aspire One netbook. Running Karmic with jack compiled
> by hand, version 0.118.0

-- 
torben Hohn
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