[LAU] Netjack questions

Len Ovens len at ovenwerks.net
Mon Jan 12 22:50:33 UTC 2015

On Mon, 12 Jan 2015, Russell Hanaghan wrote:

>> At work I've been using zita-njbridge with the default 10 ms buffering
>> over a wireless LAN. I don't think this can be repeated easily (I'm
>> working at Huawei Research so networks can be assumed to be performing
>> well). OTOH using a Cat6 cable and decent NICs this should just work.
>> Latency may still be too high for in-ear monitoring.
> I understand. I'm not too worried about the network side of stuff. I've 
> a variety of gear and have a long background associated to network 
> infrastructure. Is < 10ms possible in a stable fashion using the netjack 
> and your zita bridge? Even half that might be ok. It's a small stAge and 
> room is mostly brick (from 1886!!) with wood floor n ceiling. Some xtra 
> minor 'slap back' might be tolerable given difficulty hearing on stage 
> next to a bloody drum kit & guitar amps!

I would suggest zita bridge would be better for these reasons:

- jackd with a -net backend will crash/exit if the network connection 
fails even temporarily. zita bridge keeps reconnecting at both ends and jackd 
keeps running anyway.

- you need the audio interface at both ends anyway and would need to run 
either alsa-in/out or zita-a2j/j2a at one end at least. Using 
zita-netbraidge already includes that.

Netjack if compiled with opus, might handle wireless a bit better if audio 
quality can suffer somewhat. Opus minimum latency is 5ms.

Latency... by the time I get 30 feet away from the band, my notes sound 
slow to me. 30 feet away means from my amp as well, so effectively 60 
feet. Having my amp right beside me might make my playing sound better to 
me, but worse to the rest of the band  :) The average pipe organ has 
longer distances and the player can deal with that... even most stages are 
wider. SO try and see. The general rule seems to be audio IF latency times 
three for the network. So USB IFs might be too slow (actually I find 
Intel HDA is often worse).

I think it would be a great test though. Try the wireless first. There may 
be some dropouts and other oddness, but so long as there are not loud pops 
that hurt the ear, it may be ok for monitoring. Opus hides dropouts as 
best it can.

Len Ovens

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