[PD] Pd and RME HDSP alsa vs jack performance

[Federico Galland]

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 ?

Is the HDSP a PCI interface? If so, pay particular attention to the "pci bus latency" part.

Also, make sure you disable your wifi card since that is known to cause dropouts. For further assistance, you may also want to inspect the linux audio users mailing list, and linuxmusicians.com forum.

My 2 cents anyway

-- 
Federico Galland <federicogalland at gmail.com>