[LAD] Jack audio questions to aid in my development of audiorack

[Ethan Funk]

> On Sat, Nov 16, 2019 at 02:47:26PM -0700, Ethan Funk wrote:
> > 1. With the low-latency kernel, jack dropouts/underruns are a
> > problemwhen jack is configured to bridge to pulseaudio.  Without a
> > pulseaudiobridge, the dropout are nonexistent.
> 
> I'd suggest to get rid of pulseaudio. It doesn't do anything
> usefulfor an application like yours.

Getting rid of pulseaudio is probably the right thing to do.  Thanks
for pushing me in that direction.

> > 2. I have a similar issue with zita-a2j and zita-j2a with lost
> > ofdropouts on the ALAS side, even though the jack side shows no
> > overruns.
> 
> How does this show up (i.e. how do you know it is the ALSA side) ?

It shows up as broken audio to/from the device, with no under-runs
logged by jack. All the rest of the jack audio flow is unaffected.

> What do you get with the -v option ?

I don't know because I am using Ubuntu Studio Control to manage the
create of zita-j2a/a2j instances on my test system.  I wanted an "easy"
way for potential users to set up jack and Ubuntu Studio Control is
nice and easy.  zita bridges are working fine on my development
machine, where I manually set them up, so there must be something in
how Ubuntu Studio Control is spawning the zita bridges.  That's why I
am also looking for the source code for Ubuntu Studio Control.  Ubuntu
Studio Control make jack setup supper simple, and almost a pleasure for
the average user.  

> > Can extra buffering be applied to the zita programs?  Maybe that
> > iswhat the -n option is for?
> 
> Using more periods could hide the problem, but it's never a
> realsolution.
> Are you sure things are running with real-time scheduling ? 

Yes.
ps -eLfc shows FF for for the scheduling policy of at least one of the
threads in the processes of interest.

> This requires some configuration in /etc/security/limits.conf,as well
> as for Jack itself.

I had gone down that road originally on the machine I am using for
development.  On my test system, I used the Ubuntu Studio Installer,
which does a very nice, friendly job of setting up a stock Ubuntu
machine for use with jack.

> Why do you need zita-a2j/j2a anyway ? Using a single multichannelcard
> is usually the better solution.

I have one multichannel audio interface for everything important:
program out, studio monitors, headphones, guest mic, host mic,
etc.  But it sure is nice to be able to use the built-in audio for a
cue channel and talkback mic, where latency is not important.  Also
handy for USB turntables, and other random devices that are
occasionally used in a radio show without latency being important.

Thanks,
Ethan...


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.linuxaudio.org/archives/linux-audio-dev/attachments/20191116/bb00f06e/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 833 bytes
Desc: This is a digitally signed message part
URL: <https://lists.linuxaudio.org/archives/linux-audio-dev/attachments/20191116/bb00f06e/attachment.sig>