linuxaudio.org

Paul Davis wrote:

quoted text
> On Tue, Jun 14, 2011 at 3:11 AM, Aaron Krister Johnson

>  wrote:

>> Hey all,

>> So the continuing saga is this: still no luck getting Pianoteq with JACK to

>> equal or spank with superiority the performance of PianoTeq w/ALSA alone on

>> my system.....[...]

>> So...here's my dilemma. I have a live show coming up where I'd prefer to use

>> the superior harpsichord sound of Pianoteq, but I don't want to risk a

>> lock-up or xruns or worse in a live concert. So I would have to use

>> ALSA...BUT....I also need to switch to playing a live kalimba through some

>> Csound effects right after playing a harpsichord, and Pianoteq under ALSA

>> will not stand for another app opening and sharing the soundcard like JACK

>> will allow (ALSA will block I/O).

>> So what can I do?

> only all the usual deeply unpleasant, deeply technical stuff related

> to figuring out sources of scheduling latency on your system. as i

> mentioned previously, JACK requires that your system can context

> switch efficiently and without delay. lots of people (including me)

> have systems that have issues with this. its caused by a tangled

> thicket of interactions between the motherboard, the PCI bus, the

> kernel and some userspace stuff. there is no magic bullet that will

> fix a given system.

>

> case in point: i dramatically improved things on my system yesterday

> by switching from the open source nouveau driver for my nvidia card to

> the proprietary one.

I can second that one which improved things on my laptop. Sad as it may

be the binary drivers seem to deliver better general system performance

than the nouveau ones.

Another one I experienced (again working with intensive Pd stuff) was to

ensure that all "CPU scaling" stuff was set to maximum performance and

nothing automatic is going on (such as "Ondemand" et sim.) both CPU-wise

*and* graphics card GPU-wise (this can e.g. be controlled in the

nvidia-panel for the proprietary drivers).
All this, of course, after taking care of the 'usual' real-time

settings. This not only on the jack/audio side: e.g. even if jack is

running realtime with bleeding edge low latency your software may not be

playing well rt (I experienced this with Pure Data were an explicit -rt

command line switch is needed to get smooth rt performance).
Anyway good luck :)

Lorenzo.
> i can now run JACK down at -p 64 -n 2 and

quoted text
> dragging windows around or moving the mouse back and forth across the

> boundary between two monitors no longer causes gaps in the audio

> (which it used to be able to do even without xruns, suggesting PCI bus

> issues). but still, after 12 hours of the new system, i still have 654

> xruns. this is on a very, very powerful 6-core system but without an

> RT kernel.

>

> --p

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