linuxaudio.org

--485b390f792abbdd5604cfe5289e

Content-Type: text/plain; charset=ISO-8859-1
simple answer: non-RT things need more buffering between them and the

hardware. find out how to do that.
On Sun, Dec 2, 2012 at 4:00 PM, Ken Restivo  wrote:
> OK, I know I've been using Linux audio for 6 years now, and gigged and

quoted text
> recorded with it extensively for most of those, yadda yadda. But it seems

> I've had an embarassingly huge hole in my knowledge the whole time.

>

> I was under the impression that, in order to use real time

> priorities/permissions and Ingo kernels, it was required for the process

> ITSELF early in the main() routine of its source code, to make some system

> calls to claim RT priority. In fact, I specifically remember reading or

> even writing source code in C which did that (probably based on JACK sample

> code). I don't recall the name of the syscall, but it was something obvious

> and well-documented.

>

> Also, I remember that it was also required that the software behave

> properly in order to be real-time capable, something about callbacks taking

> some predictable amount of time. Or perhaps that was only a JACK

> requirement.

>

> Why am I asking these dumb-ass questions now? Because I've been playing

> around with Liquidsoap and Airtime for some radio stations, and I'm

> obsessed with getting them as rock-solid on cheap/free/old hardware as I'd

> been able to get with my gigging and studio synths.

>

> It physically pains me to hear audio stuttering because Apache is running

> on the same box. It seems an outrage to me. Shouldn't happen. Ever. I used

> to record and mix multi-track songs in Ardour with tons of soft-synths

> WHILE A KERNEL COMPILE WAS GOING ON THE SAME MACHINE without a single

> glitch. I expect no less.

>

> So I asked on the Liquidsoap list, and I got only shrugs and a pointer to

> the Gentoo page in response (why? I have no idea. I use Debian, and that's

> irrelevant to the question at hand anyway.).

>

> So what's the deal? Is there a way to give Ingo-approved preemptive RT

> priority to things that aren't real-time apps and aren't specifically

> architected for that? What, if anything, would break?

>

> And, if I wanted to hack Liquidsoap (which would require learning ML,

> which wouldn't be a bad thing to know anyway), is it even possible to get

> it RT-capable, or are there low-level C system calls required in order to

> make that work?

>

> Sorry for the long and obscure question, but it's been bothering me for a

> while, and I figured someone here would know the answer, or where I might

> find it.

>

> Thanks.

>

>

> -ken

> _______________________________________________

> Linux-audio-user mailing list

> Linux-audio-user@lists.linuxaudio.org

> http://lists.linuxaudio.org/listinfo/linux-audio-user

>

--485b390f792abbdd5604cfe5289e

Content-Type: text/html; charset=ISO-8859-1

Content-Transfer-Encoding: quoted-printable
simple answer: non-RT things need more buffering between them and the hardw=

are. find out how to do that.On Sun, Dec 2, 2012 at 4:00 PM, Ken Restivo <ken@resti=

vo.org> wrote:

OK, I know I've been using Linux audio f=

or 6 years now, and gigged and recorded with it extensively for most of tho=

se, yadda yadda. But it seems I've had an embarassingly huge hole in my=

 knowledge the whole time.
I was under the impression that, in order to use real time priorities/permi=

ssions and Ingo kernels, it was required for the process ITSELF early in th=

e main() routine of its source code, to make some system calls to claim RT =

priority. In fact, I specifically remember reading or even writing source c=

ode in C which did that (probably based on JACK sample code). I don't r=

ecall the name of the syscall, but it was something obvious and well-docume=

nted.
Also, I remember that it was also required that the software behave properl=

y in order to be real-time capable, something about callbacks taking some p=

redictable amount of time. Or perhaps that was only a JACK requirement.
Why am I asking these dumb-ass questions now? Because I've been playing=

 around with Liquidsoap and Airtime for some radio stations, and I'm ob=

sessed with getting them as rock-solid on cheap/free/old hardware as I'=

d been able to get with my gigging and studio synths.
It physically pains me to hear audio stuttering because Apache is running o=

n the same box. It seems an outrage to me. Shouldn't happen. Ever. I us=

ed to record and mix multi-track songs in Ardour with tons of soft-synths W=

HILE A KERNEL COMPILE WAS GOING ON THE SAME MACHINE without a single glitch=

. I expect no less.
So I asked on the Liquidsoap list, and I got only shrugs and a pointer to t=

he Gentoo page in response (why? I have no idea. I use Debian, and that&#39=

;s irrelevant to the question at hand anyway.).
So what's the deal? Is there a way to give Ingo-approved preemptive RT =

priority to things that aren't real-time apps and aren't specifical=

ly architected for that? What, if anything, would break?
And, if I wanted to hack Liquidsoap (which would require learning ML, which=

 wouldn't be a bad thing to know anyway), is it even possible to get it=

 RT-capable, or are there low-level C system calls required in order to mak=

e that work?
Sorry for the long and obscure question, but it's been bothering me for=

 a while, and I figured someone here would know the answer, or where I migh=

t find it.
Thanks.
-ken

_______________________________________________

Linux-audio-user mailing list

Linux-audio-user@l=

ists.linuxaudio.org

http://lists.linuxaudio.org/listinfo/linux-audio-user
--485b390f792abbdd5604cfe5289e--