[PD] a/d/a and jackd alsa low-latency problems

[guenter geiger]

On Wed, 20 Oct 2004, vanDongen/Gilcher wrote:
> On Tuesday 19 October 2004 07:40, Frank Barknecht wrote:
>
> >
> > Whooho, 64 already is *very* small. I never heard of anybody run jack with
> > 32. That's almost hard-realtime!
> >
>
> Several people are running jack with -p8 or -p16 using the latest
> realtime-preempt patches on linux 2.6.9

Just want to add that this "feature" depends primarily on the soundcard.
Mine (SBLive) for example has a minimum of -p512.

If ALSA says it cannot set periodsize, then it can't, unless you change
your soundcard hardware.
And then there is the minimum latency implied by pd. Going beyond
64 does not make sense with pd. Sound I/O with pd is based on
64 bit chunks.

Guenter

> I can run -p16 without xruns on 2.6.9-rc4-mm1 as long as I don't use
> disc-access, that's even without ingo's latest harder realtime patches.
> (Of course if I don't do anything, no apps, no X, just start jackd, I can go
> to -p8. But that is really pointless, but neat.)
> I'll try the latest patches and do the latency-limbo, how low can you go.
>
> The downside is that periodsizes that small are less efficient for synthesis,
> so the same thing takes more cpu and you hit your performance ceiling sooner
> In a way it is useless to go that low, but it does mean that the entire system
> is more robust, so bigger periods will perform better as well.
>
> ciao
>
> Gerard
>
> > Ciao
>
> --
> electronic & acoustic musics-- http://www.xs4all.nl/~gml
>
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