Re: [LAD] ALSA multi plugin and JACK xrun callbacks

hi!

sorry for warming up an older thread here...

On 12/16/2010 04:21 AM, Lee Azzarello wrote:
> Hello, I'm looking for some advice for an interesting symptom of
> putting my M-Audio Fast Track Pro USB sound card into ALSA multi mode.
> This sound card has four physical outputs which are mapped to two 2
> channel ALSA streams rather than one four channel stream. I used the
> ALSA multi plugin to combine these two streams into a single pcm
> device so JACK can interface with all four outputs. It is working
> nicely.
>
> Despite no perceptible problems in sound quality or latency, jackd is
> printing hundreds of XRUN callback warnings to the message console
> each second! I can operate the system perfectly fine, run multiple
> applications, connect them to the four virtual outputs with no audible
> timing issues.
>
> What is the meaning of this many XRUN callbacks per second? What kind
> of performance will this impact if not sound playback?

i've just tried to link a hdspm (using faberman's driver) and an ancient
digi9652 into a monster 90 channel device.

my .asoundrc looks like this:

pcm.multi {
    type multi;
# the hdspm: first 64 channels
    slaves.a.pcm "hw:2,0";
    slaves.a.channels 64;
# the digi9652: last 26 channels
    slaves.b.pcm "hw:1,0";
    slaves.b.channels 26;

    bindings.0.slave a;
    bindings.0.channel 0;
    ...
    bindings.63.slave a;
    bindings.63.channel 63;

    bindings.65.slave b;
    bindings.65.channel 0;
    ...
    bindings.90.slave b;
    bindings.90.channel 1;
}

ctl.multi {
    type hw;
    card 2;
}

the two cards are synced via wordclock at 48k, the hdspm is the master.

miraculously enough, i can actually start jack with this device:

22:06:48.259 ALSA connection graph change.
22:06:48.393 ALSA connection change.
22:11:42.707 JACK is starting...
22:11:42.708 /usr/local/bin/jackd -P80 -p2048 -t9999 -u -dalsa -dmulti
-r48000 -p1024 -n2 -zs
Cannot connect to server socket err = Connection refused
Cannot connect to server socket
jack server is not running or cannot be started
no message buffer overruns
no message buffer overruns
jackdmp 1.9.7
Copyright 2001-2005 Paul Davis and others.
Copyright 2004-2010 Grame.
jackdmp comes with ABSOLUTELY NO WARRANTY
This is free software, and you are welcome to redistribute it
under certain conditions; see the file COPYING for details
JACK server starting in realtime mode with priority 80
22:11:42.844 JACK was started with PID=28260.
creating alsa driver ... multi|multi|1024|2|48000|0|0|nomon|swmeter|-|32bit
Using ALSA driver HDSPM running on card 2 - RME MADI S/N 0xc62105 at
0xf9ff0000, irq 19
configuring for 48000Hz, period = 1024 frames (21.3 ms), buffer = 2 periods
ALSA: final selected sample format for capture: 32bit integer little-endian
ALSA: use 2 periods for capture
ALSA: final selected sample format for playback: 32bit integer little-endian
ALSA: use 2 periods for playback
22:11:45.082 JACK connection change.
22:11:45.220 Server configuration saved to "/home/nettings/.jackdrc".
22:11:45.222 Statistics reset.
22:11:45.238 Client activated.
22:11:45.341 XRUN callback (1).
22:11:45.341 JACK connection graph change.

and like lee, i immediately get hundreds of "little xruns", i.e. the
type that qjackctl displays in parentheses. the "big" xrun count stays
at zero. meanwhile, i'm getting these errors in the log:

JackPosixMutex::Unlock res = 1
JackPosixMutex::Unlock res = 1
JackPosixMutex::Unlock res = 1

i had it crash once when loading a really demanding session, but with
another average ardour project, it has now played fine and without
glitches for 10 minutes or so, while the xrun count goes through the roof.

i wonder what's really going on here, but i'm also happy i can combine
those two cards which means i finally get a Grand Unified interface
without the need to restart jack, ever again :)

best,

jörn

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Received on Sat Jan 15 00:15:07 2011