Re: [linux-audio-user] connecting soundcards using JACK

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Subject: Re: [linux-audio-user] connecting soundcards using JACK
From: Eric Dantan Rzewnicki (rzewnickie_AT_rfa.org)
Date: Tue Nov 09 2004 - 21:11:37 EET


On Tue, Nov 09, 2004 at 02:47:18PM +0100, Jeroen Wijnhout wrote:
> On Tuesday 09 November 2004 05:29, Nathan Callahan wrote:
> > It's not possible to start jackd on more than one soundcard. You can,
> > however use ecasound's jack output to kind of simulate it.
> > Start jackd on the AC97 card, then issue the command:
> > ecasound -B:rtlowlatency -f:s16,2,44100 -z:nomultitrack -z:nointbuf
> > -o:jack -i:alsa,<iMic ALSA device>
> > This is based on a script that I had set up to do something similar. I
> > can't quite remember why all of those options are there, so they might
> > not be necessary.
> > This may be a little unstable, but it's much better than trying to keep
> > the soundcards synced properly. No guarantees, YMMV.
> Thanks for the tip. It sounds promising, but I don't get it to work properly.
> I've started jackd with:
> jackd -Rv -d alsa -d default -p 512 -n 3 -r 44100
> Everything runs fine (no xruns).
> Then I start ecasound as you mentioned, which after a 10 seconds or so says:
> - [ Engine init - Driver start ] -------------------------------------------
> (eca-engine) Using realtime-scheduling (SCHED_FIFO).
> (audioio-alsa) warning! playback overrun - samples lost! Break was at least
> 6.66 ms long.
> zombified - calling shutdown handler
> - [ Controller/Batch processing finished ] ---------------------------------
> - [ Engine exiting ] -------------------------------------------------------
> (eca-controller) Disconnecting chainsetup: "command-line-setup".
> (audioio-jack-manager) Connection closed!
> - [ Chainsetup disconnected ] ----------------------------------------------
> (audioio-alsa) WARNING! While reading from ALSA-pcm device C0D0, there were 1
> overruns.

You may be able to twiddle with the options and get different results
from a settup like this, but I doubt you will ever get good results. You
are still asking ecasound to take 2 different clock sources and mesh
them together. It's unlikely that this will ever work without causing
xruns.

-Eric Rz.


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