Re: [Jack-Devel] ALSA PCM multi plugin and xruns

Hi Paul,

On Tue, Dec 11, 2012 at 10:15 AM, Paul Davis <[hidden]> wrote:

>> In the long term, I don't think this is the best way to solve this
>> issue.  The multi device is inherently broken because of the
>> assumption that only one card needs to be polled.  I think a better
>> way to solve this problem would be to write a new JACK driver that
>> aggregates the cards itself (no multi device), and waits until I/O is
>> available on both cards.
>
>
> jackd  [ ... args ... ] -d alsa -d hw:FIRST &
> alsa_in [ ... args ] -d hw:SECOND &
> alsa_out [ ... args ] -d hw:SECOND &
>
> [ .. repeat as needed]
>
> much more general than your brief summary, since alsa_in/alsa_out will
> resample as necessary, thus not requiring that the devices share a sample
> clock.

It's my understanding that `alsa_in` and `alsa_out` add some latency,
which means that sound card that JACK is synced to and the sound card
that the alsa-in/out clients use aren't quite in sync.

> now of course, if the devices are synced then none of this would be
> necessary. if they are synced and ALSA gets things things wrong, the ALSA
> needs fixing.

What about cases where the word clock sync of a sound card isn't quite
as tight as it should be?  Does ALSA have control over that?

-- 
Devin Anderson
surfacepatterns (at) gmail (dot) com

blog - http://surfacepatterns.blogspot.com/
psinsights - http://psinsights.googlecode.com/
synthclone - http://synthclone.googlecode.com/

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