[LAU] Re: Pops and clicks but no xruns

[Karl Hammar]

James Stone <jamesmstone at gmail.com>:
> On Sun, Apr 08, 2007 at 01:38:34PM +0200, Karl Hammar wrote:
> > Andrew Burgess <aab at cichlid.com>:
> > > Paul Davis wrote:
> > > >> What could cause clicks without xruns? I'm baffled.
> > > >PCI bus hogging, for one thing. consider running a script like this
> > ...
> > >     setpci -s $p latency_timer=ff
...
> I am slightly confused. Is it necessary to increase the latency
> timer for a pci sound card? This seems slightly
> counter-intuitive. Wouldn't this reduce the performance of the
> sound system through that card?

Performance and latency is different things. In audio we accept all 
latencies below 30ms (I think), less than that does not gain anything.

But we can gain bandwith by using longer bursts, thus a higher latency 
(within bounds) gives us greater performance.

> The only thing the above script changes on my system is the
> latency of the SB Live.

Yes, I missed the general setting seen below.

Paul Davis in the message that started this thread:
>#!/bin/sh
>
>case $1 in
>     start)
>           # "open up" the PCI bus by allowing fairly long bursts for
>all devices, increasing performance
>           setpci -v -s "*:*.*" latency_timer=b0
>           # maximise latency for RME Hammerfall, thus allowing
>           # more data per PCI transfer and minimizing xfuns
>           setpci -v -s 01:04.0 latency_timer=ff
>           # ditto for the onboard AC97 audio interface
>           setpci -v -s 00:07.5 latency_timer=ff
>esac

Regards,
/Karl

-----------------------------------------------------------------------
Karl Hammar                    Aspö Data               karl at aspodata.se
Lilla Aspö 2340                                                Networks
S-742 94 Östhammar          +46  173 140 57                   Computers
Sweden                     +46  70 511 97 84                 Consulting
-----------------------------------------------------------------------