Re: [ecasound] Cannot connect to JACK Ecasound with Jack - 'Error! Cannot connect to JACK ... server!'

From: Kai Vehmanen <kvehmanen@email-addr-hidden>
Date: Sun Apr 17 2005 - 15:37:28 EEST

On Fri, 15 Apr 2005, Free Lunch wrote:

> Something bad happened at one point.. My first WAV ended at 471707692
> bytes. Fortunately, I ran everything under wrapper scripts to
> automatically re-start any applications that failed (jackd, ecasound,
> ecasignal). Unfortunately, I didn't log the output from the software
> so there isn't really any diag info available.

I recommend running long test runs with the same exact setup, and try
to see if you can recreate the problem. If jackd is run with strict
settings, the system has to be fairly well tuned so that it runs without
glitches for long periods of time. On the bright side, once tuned, jackd
runs does run reliably.

You should also watch out for system events: heavy X screensavers,
logrotated, updatedb and etc cron runs. These won't necessarily cause
problems to audio, but still they cause unnecessary extra load that you
don't when doing audio work. I once had updatedb running during a JACK
demo at one event, and even though window drawing was _very_ slow, audio
played without glitches the whole time! Of course during the demo no idea
on what in the world was happening with the system - I had just tested the
whole demo on the same hw the day before. :)

> One serious glitch occurs when I terminate ecasignalview with an
> interrupt. It often causes ecasoundview to also terminate (and my
> recording!). I assume that is not expected behavior? I think there
> was a message about 'audio chain broken'. I will try and reproduce.

A known design limitation of JACK is that changing connections can cause
glitches to audio (in the same way as plugging analog mixer cables can
cause pops ;)). Other client connections should not be broken, but in
practise it often happens - especially other clients connected to same
ports as the ones you've disconnected, might need to be reconnected. There
have been some proposal how to address these problems, so situation might
improve in later JACK releases (=> but not before 1.0).

> I would still like to run ecasound and ecasignalview simultaneously
> without Jack, if that is possible. Simpler is better in these cases.

You can use the ALSA dsnoop plugin:
-> "Software mixing" -> "dsnoop"

Copy and paste the "pcm.mixin" definition to your ~/.asoundrc and
then you can do:

ecasound -i alsa,mixin -o foo.wav
ecasignalview alsa,mixin null

At least on my system, I don't get any glitches when I start and stop
multiple apps using the 'mixin' device.

In addition to the above link, another good resource to learn about
asoundrc is:

I'm no expert with this stuff, so I recommend subscribing to alsa-user
mailing list if you have any tricky questions about asoundrc. :)

  Audio software for Linux!
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Received on Sun Apr 17 16:15:07 2005

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