Re: [LAD] zita-ajbridge and aloop

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To: <linux-audio-dev@...>
Date: Wednesday, July 17, 2013 - 8:09 pm

On Wed, Jul 17, 2013 at 05:21:12PM +0200, IOhannes m zmoelnig wrote:

> when running zita-a2j resp. -j2a in verbose mode, i understand that

It's not that bad, it just indicates that there is some timing
jitter. This can happen for a variety of reasons, see below.

> more troubling however, is that whenever i start an alsa application

You could try playing with the value in jclient.cc, line 437
to avoid this. Note that the delay error value printed by -v
is averaged over 1/4 second, while the one tested is not.

> (btw, i'm using robin's jackd2-1.9.10+nobus+20130114gite4730c6c-NMU1)

This is really a combination of all possible worst-case scenarios.

* Does your HW have a high resolution timer that Jack can use
for its microseconds timer ? If not there will be trouble.

* Same for the aloop device. It emulates a HW device at some
configured sample rate, and therefore depends on an accurate
timer in order to do this without loads of jitter.

* I have *no* idea of the correct implementation of the DLL used
in Jack2, but zita-ajbridge does critically depend on it.

* For anything USB, 44.1 kHz is really asking for trouble. With
48 kHz you have at least a a simpler relation to the USB interrupt
rate of 1 kHz, and if that doesn't help using -n 3 probably will.
I don't know 'Andrea Electronics'...

* Keep in mind that zita-ajbridge was not designed to be used
this way. Its primary use is to add an additional (decent)
soundcard to Jack, and I have my doubts about aloop.

> finally: i'm wondering a bit on how to choose proper values for

For Jack vs. zita-*2* there are no restrictions. In normal use
(that is adding a real sound card to Jack), you would make the
period size of zita-*2* shorter than the one used by Jack
(unless that is already quite small) to avoid additional latency.

I don't know how having different period sizes on both ends of
an aloop would affect it.

Ciao,

--
FA

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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Messages in current thread:
[LAD] zita-ajbridge and aloop, IOhannes m zmoelnig, (Thu Jul 11, 1:59 pm)
Re: [LAD] zita-ajbridge and aloop, Dominique Michel, (Thu Jul 11, 6:49 pm)
Re: [LAD] zita-ajbridge and aloop, Joel Roth, (Fri Jul 12, 12:52 am)
Re: [LAD] zita-ajbridge and aloop, Dominique Michel, (Fri Jul 12, 9:17 pm)
Re: [LAD] zita-ajbridge and aloop, Fons Adriaensen, (Thu Jul 11, 3:58 pm)
Re: [LAD] zita-ajbridge and aloop, IOhannes m zmoelnig, (Mon Jul 15, 11:46 am)
Re: [LAD] zita-ajbridge and aloop, IOhannes m zmoelnig, (Wed Jul 17, 3:21 pm)
Re: [LAD] zita-ajbridge and aloop, Fons Adriaensen, (Wed Jul 17, 8:09 pm)
Re: [LAD] zita-ajbridge and aloop, IOhannes m zmoelnig, (Wed Jul 17, 3:29 pm)