Re: [LAU] How to make Jack remember soundcards, not alsa-slots

On Tue, Dec 14, 2010 at 12:55:11PM -0500, Joe Hartley wrote:
> On Tue, 14 Dec 2010 18:23:47 +0100
> torbenh <torbenh@email-addr-hidden> wrote:
> > On Tue, Dec 14, 2010 at 11:55:03AM -0500, Joe Hartley wrote:
> > > If you want to use these two cards together, then syncing with SPDIF is
> > > pretty much required. The alsa_in/out programs add latency, and as the
> > > website said, you should not record using those programs.
> >
> > alsa_in/out programs can yield lower latency than jackd itself.
> > and i doubt, that anyone can hear the artifacts.
> >
> > the website is for the version that came with jack 0.116.x
> > but the new algorithm is a lot better.
> >
> > > I can guarantee that you'd need to sync them with SPDIF under Windows as
> > > well as Linux, or you'll get clock drift between the cards.
> >
> > alsa_out tools are build to compensate the clock drift.
>
> Fairly impressive performance, then! I'm not likely to revamp my setup
> (Don't fix what isn't broken!) but do you feel this is fast and stable
> enough for studio use?
>
> My skeptical side feels that a software solution to sync the cards will
> always be inferior to using hardware-based master/slave clocking, but it's
> entirely possible that systems are more than fast enough to handle this easily.

the cards are not synced.
the program just compensates for the drift.
it does this by slightly resampling the stream.

if you can hardware sync your cards, then by all means do it. its
better. alsa_io will burn quite a bit of cpu.
its just normally is the easiest solution, and works without hardware
sync.
and the claim that it adds latency is wrong.

>
> I'm not sure I'd want to rely on it for recording 16 channels of 24 bit/96kHz
> input, though - at least on my rather aging but quiet and stable P4 based
> studio system.

>
> --
> ======================================================================
> Joe Hartley - UNIX/network Consultant - jh@email-addr-hidden
> Without deviation from the norm, "progress" is not possible. - FZappa
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-- 
torben Hohn
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