[linux-audio-dev] mux concept paper

Steve Harris S.W.Harris at ecs.soton.ac.uk
Thu Feb 17 14:29:01 UTC 2005

On Thu, Feb 17, 2005 at 02:00:24 +0000, mimo wrote:
> Paul Davis wrote:
> >
> >>complaining. But my experiences with jack are negative. First time I 
> >>started looking at it I had huge expectations after all that I had read. 
> >> First problems, after a couple of second of running without any 
> >>actual processing going on, strange noise artefacts kind of getting 
> >>worse. I had a look at source code and realise that it bases its time 
> >>calculation on cpu MHz in /proc/cpuinfo. I dont know about your machine, 
> >>but on my machine(s) a) this is a float and b) it's slightly different 
> >>every time I boot the machine.
> >
> >
> >this has nothing to do with your noise. JACK uses CPU Hz to provide a
> >UST value. i am puzzled by the fact you are the 2nd person to think
> >that JACK's timing is somehow based on system timers and so
> >forth. JACK (in regular mode, using one of the normal backends) is
> >driven 100% by the interrupt from your audio interface. whether or not
> >the CPU Hz value is correct has (effectively) zero impact on audio
> >generation and timing.
> Just out of interest, if it is dependent on the audio hardware, why do I 
> get the same problems with different sounds cards on the same machine, 
> and a colleague gets them with completely different hardware all the 
> same. Any ideas what might be the reason? Anyone else with the same 
> experiences?

Are you running it in realtime mode? If not, and jackd misses realtime
deadlines you will often get noises in the output.

- Steve

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