[linux-audio-user] Jackstart - realtime capabilities issues

[Robert Jonsson]

Hi Rachel,

måndagen den 16 februari 2004 22.31 skrev RachelAPP:
> I knew i'd come back with more questions sooner or later...!
>
> OK, here's my setup:
> Debian
> Kernel 2.4.22
> Terratec DMX6 Fire (working properly with Alsa driver now - at least, i can
> record with Audacity)
> Evolution MC225C Midi controller (plugged into my Terratec Midi input)
> My computer is a AMD 2400XP, 512 MB RAM
>
> I have installed Muse as recommended by somebody and also Jack and when i
> typed "jackstart --help" in the shell i got this (running as root)
>
> jackstart: cannot get realtime capabilities, current capabilities are:
>            =ep cap_setpcap-ep
>     probably running under a kernel with capabilities disabled,
>     a suitable kernel would have printed something like "=eip"
>
> I haven't installed Linux myself on my computer - a friend did it and
> explained to me what he was doing while he was doing it but obviously, i
> might not know everything about my setup. We installed it starting with
> Knoppix then upgraded it to Debian. We tried to install the Kernel 2.6
> afterwards but it doesn't boot, probably due to a video card error because
> the screen actually goes blank even though i can hear the hard drive is
> working.
>
> So i have a couple of questions:
>
> 1) is there a quick fix for my jackstart problem with my current kernel?
Probably your kernel isn't correctly configured for capabilities but since you 
are already running the app as root you do actually not need it.

Capabilities is a way to grant normal users some extra privileges, in this 
case, the need for running applications with real-time scheduling enabled.

When you start the app as root you don't need that since you already have 
_all_ privileges.

Try starting jack directly.

for instance:

jackd -d alsa -d hw:0


> 2) should i upgrade to kernel 2.6?

You should probably wait until 2.6 is more stable, all you need is there 
already. 

...Though you may wish to recompile the kernel (or install a precompiled one) 
with low-latency patches enabled (if you don't have those already). I don't 
know what is available for debian, someone else might enlighten you.

Another stumbling block may be audio drivers, atleast knoppix did previously 
only support the OSS audio drivers, since you upgraded to debian it might 
have fixed itself though. 
Anyway, the ALSA driver package is a requirement to get the setup you are 
talking about to work. It should be visible in the boot up if you got ALSA or 
OSS.

Regards,
/Robert