[LAU] usb and jack

[hollunder at gmx.at]

On Sun, 25 Oct 2009 18:03:09 +0800
Ray Rashif <schivmeister at gmail.com> wrote:

> 2009/10/25 <hollunder at gmx.at>
> 
> > On Sun, 25 Oct 2009 11:40:16 +0100
> > rosea grammostola <rosea.grammostola at gmail.com> wrote:
> >
> > > Hi,
> > >
> > > I found this info:
> > >
> > >
> > >       "USB and jack
> > >
> > > The USB interrupt period is 1 msec. To be able to get lower
> > > latency with jack when using it with an USB device, you have to
> > > use a setting as 48kHz and 3 period. It will makes the buffer
> > > time a multiple of 1 msec and you will get a much lower latency
> > > as with the default 2 period. Additionaly, loading the
> > > snd-usb-audio with the parameter "nrpacks=1" will give you a much
> > > lower latency (for this to work take care that
> > > CONFIG_USB_BANDWIDTH is not set and CONFIG_USB_DYNAMIC_MINORS is
> > > not set in your running kernel)."
> > >
> > >
> > >
> > http://proaudio.tuxfamily.org/wiki/index.php?title=Howto_RT_Kernel#USB_and_jack
> > >
> > >
> > > 1) is this info still up-to-date?
> > > 2) how do I exactly take care of this:
> > > "Additionaly, loading the snd-usb-audio with the parameter
> > > "nrpacks=1" will give you a much lower latency (for this to work
> > > take care that CONFIG_USB_BANDWIDTH is not set and
> > > CONFIG_USB_DYNAMIC_MINORS is not set in your running kernel)"
> > >
> > > (Debian (based) systems)
> > >
> > > \r
> >
> > In my experience 48kHz/3 periods works a bit more stable, the
> > possible latency settings in jack don't really change, 64 frames is
> > still the lower boundary and unstable.
> >
> > But I haven't heard about  2)  and am very curious about this
> > myself.
> >
> > Philipp
> 
> 
> 2) Edit /etc/modprobe.conf or /etc/modprobe.d/modprobe.conf with:
> 
> options snd-usb-audio nrpacks=1
> 
> And to "make sure". you have to have the kernel options changed. make
> menuconfig, and press "/" to search for the two options.
> 
> Philipp: we already dealt with that one but _without_ substantial
> cause-and-effect http://bugs.archaudio.org/task/5

Thanks, you're right, CONFIG_USB_DYNAMIC_MINORS is not set and CONFIG_USB_BANDWIDTH doesn't
even show up.

I'll try to load with that option tomorrow and see how it goes.

Philipp