[PD] Pd and RME HDSP alsa vs jack performance

Peter P. p8rpp at aol.com
Wed Apr 16 00:40:31 CEST 2014


* Federico Galland <federicogalland at gmail.com> [2014-04-15 17:46]:
> On Tue, 15 Apr 2014 16:07:03 -0400
> "Peter P." <p8rpp at aol.com> wrote:
> 
> > Hi list,
> > 
> > following up onto some earlier postings I had made about the current
> > problems running Pd with any buffersize larger(!) than 5 using alsa,
> > the mmap code and an RME HDSP Multiface on Debian Linux, here are some
> > more results from tests I made recently:
> > 
> > Alsa only works with audiobuf smaller 6, otherwise causing totally
> > garbled sound. With that short buffer settings it is unusable for
> > everything more CPU intense than sine test tones though.
> > 
> > The only way to get Pd to run reliably under some load on my box using
> > the HDSP is to use jack with 256 frames at 2 periods/buffer.
> > 
> > Now what is weird is that the built in soundcard of my box is able to
> > do the same thing without problems with just 64 frames at 3
> > periods/buffer in jack.
> > 
> > Again with the HDSP, once I start adding Gem and let it render a
> > single geo, I do get many audio dropouts unless I increase jack's
> > buffers to a minimum 2048 frames at 2 frames/buffer.
> > 
> > I tested this using two different HDSP cards on two different Debian
> > boxes, using the -rt flag, realtime and non-realtime kernels,
> > optional callbacks and different sleegrain setting.
> > 
> > Somehow it seems very sad that one of the best pro multichannel sound
> > cards under Linux seems to be unusable with Pd under Alsa reliably.
> > 
> > I would like to contribute to any ways of improving this situation and
> > desperately hope that someone can comment on my findings.
> > 
> > thank you!
> > best, Peter
> > 
> > _______________________________________________
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> 
> I guess you have ruled out everything under this wiki http://wiki.linuxaudio.org/wiki/system_configuration ?
Thank you Federico,
I looked at the page and most suggesstions is stuff I already
considered.
> 
> Is the HDSP a PCI interface? If so, pay particular attention to the "pci bus latency" part.
Well it is a ExpressCard interface in my case, and I wonder if that
qualifies as PCI device. The above pages mentions that PCIe devices
are not affected by the irq priorities as PCI does.

best, Peter



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