[linux-audio-dev] SBLive again

Lukas Degener AFBLukas at gmx.de
Sun May 18 11:15:01 UTC 2003

please excuse me posting to both lad and jack-dev, i wasn't sure which 
one fits better.

I am experiencing again what i may call "static crackling noises" when 
jackd with my sblive. They apear every now and then and go away after 
some time. The reason why i send this to the jack-dev list too, is that 
this does not happen when i use the same application (ams in this 
particular case, but also other jack clients like freqtweak or muse show 
this behaviour) without jack, i.e. directly interfacing the alsa layer.

So could it be that jack does something which sort of provocates this 
crackling, something that does not happen when using alsa "directly" ?

And yes, i am using a VIA chipset, first (on my old mobo) the KT133 and 
now (new mobo) the KT266. Reading through all kinds of web forums i have 
found this issues been discussed in length but without a clear result 
apart of statements like "Don't use SBLive!" or "Don't use VIA mobos!" 
(maybe both are right, but neither does much to make me feel better :-) )

Does anybody actualy _know_ what the reason for this noises is? Is there 
anything i can do? Would it help to tweak pci latency timers? I read 
somewhere that this solved the problem for someone using Win98, but i 
have to admit that even after reading two HOWTOs on this, i'm not realy 
understanding what this exactly does.

Here are some additional observations i made, maybe this is of help:

- After juggeling pci slots a bit, my sblive now uses irq 10 and does 
not share it with any other device. That did noticable  improve the 
situation, i.e. crackling does apear less frequently.

- As described above, the noise starts every now and then (i haven't yet 
found something that would proofable trigger it). First there are a few 
clicks and pops, then it becomes more "dense" and soon it sounds like 
some high frequent crackling. (dropped frames i suppose, lots of them). 
This lasts till jackd reports an x-run, and that's where it stops 
abruptly. (So there are situations when xruns become your friend :-) )
BTW, any idea how i could get more "run-time" info on what happens in my 
machine when this crackling starts? Is there a way to "see" irq activity?

- The problem does not seem to be related to system load, it happens 
even in situations where jackd reports less than 5 percent cpu usage.

- Sometimes when i create realy loud noises in ams, which result in 
hard-clipping somewhere in the signal chain, this sounds quiet similar. 
But i guess this hardly is related?

Hope this wasn't too much of a redundant question.

Kind Regards,

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