Csound RT performance on this machine I have updated is not that
great. I was running a fairly heavy orc doing phase vocoder demix,
which should have been OK and I got a stream of dropouts on the
two modules (less on Alsa, which reported constant buffer underruns).
I had a look at what the processors were doing (it's a dual machine) and
they were at 45-6%, so it was not a problem for the machine. No matter
how much I upped the buffer size (up to a reasonable level), I still got
underruns.

Any suggestions? Should I try some kernel patching?

Victor Lazzarini
Music Technology Laboratory
Music Department
National University of Ireland, Maynooth 



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I used the default outdevice (-odac) and anything from
-b64 -B512 up to -b2048 -B4096

Victor

At 15:31 13/01/2006, you wrote:
>On Friday 13 January 2006 16:22, Victor Lazzarini wrote:
>
> > Csound RT performance on this machine I have updated is not that
> > great. I was running a fairly heavy orc doing phase vocoder demix,
> > which should have been OK and I got a stream of dropouts on the
> > two modules (less on Alsa, which reported constant buffer underruns).
> > I had a look at what the processors were doing (it's a dual machine) and
> > they were at 45-6%, so it was not a problem for the machine. No matter
> > how much I upped the buffer size (up to a reasonable level), I still got
> > underruns.
> >
> > Any suggestions? Should I try some kernel patching?
>
>What output device and buffer settings did you use ?
>
>
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Victor Lazzarini
Music Technology Laboratory
Music Department
National University of Ireland, Maynooth 



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I tried -o dac:hw:0 and I could not run it, as csound
says "unable to set sample format requested",
whereas with -o dac:plughw:0 it runs as before.

The same orc runs on my Windows machine OK (with
-b1024).

What kernel are you running? Do you have a low-latency patch?

Victor

At 15:50 13/01/2006, you wrote:
>On Friday 13 January 2006 16:40, Victor Lazzarini wrote:
>
> > I used the default outdevice (-odac) and anything from
> > -b64 -B512 up to -b2048 -B4096
>
>Try using -o dac:hw:0 with -+rtaudio=alsa (-o dac:hw:1 for
>the second card, etc.). Also, PVOC with a large FFT size may
>not be friendly to low latency real time audio, due to the
>uneven CPU usage.
>
>
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Victor Lazzarini
Music Technology Laboratory
Music Department
National University of Ireland, Maynooth 



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> Csound RT performance on this machine I have updated is not that
> great. I was running a fairly heavy orc doing phase vocoder demix,
> which should have been OK and I got a stream of dropouts on the
> two modules (less on Alsa, which reported constant buffer underruns).
> I had a look at what the processors were doing (it's a dual machine) and
> they were at 45-6%, so it was not a problem for the machine. No matter
> how much I upped the buffer size (up to a reasonable level), I still got
> underruns.
> 
> Any suggestions? Should I try some kernel patching?

Hmm, I got really good results using --sched and --expression-opt and 
-+rtaudio=alsa even without the kernel patch. But the Ingo Molnar kernel 
patches definitely make a big difference too.

Iain


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