[linux-audio-dev] real time priority programming tutorial

Alex x37v.alex at gmail.com
Sun Jun 4 00:25:55 UTC 2006


Sorry to be vague, basically, what I want to do is create a timer for
an "event" sequencer I'm writing (which I will use to write music
compositions, video, etc).  I cannot find "event timers" that will
give me accuracy of less than 1ms, so I'm using a 1ms resolution event
timer and after that polling the time of day in order to get to the
time I want.  I'm trying to achieve ~256-900 event clock "ticks" per
second and minimize jitter.

First off, if anyone has advice for implementing such a timer I'd
appreciate it, but second, I'm wondering how I can make my program
have "real time" priority such that when a signal is created by this
1ms resolution event timer my app is quickly made to respond to the
signal and so this can be done as a user, [using set_rlimits, pam or
what have you (this is what i was talking about in my first email)].

Also, as I figure missed ticks are probably inevitable, I'm trying to
figure out a way to make my program robust to missed clock ticks [so
that over time i am still on beat].

Thank you,
Alex Norman

>
> On Fri, 02 Jun, 2006 at 01:06AM +0200, Jens M Andreasen spake thus:
> > On Thu, 2006-06-01 at 10:06 -0700, Alex wrote:
> > > Does anyone have a link to a reference about making apps with real
> > > time priority capabilities?
> >
> > As such there is no difference between an RT app and a not RT app,
> > except that the former varity might not work as advocated ....
>
> I think he meant: how you demand RT priority and what you should do
> not to screw it up once you have it.
>
> > > I figure I can just look at jack but it would be nice see some
> > > tutorial, to learn what is actually happening/necessary, trade-offs,
> > > etc.
> > >
> > > thanks,
> > > Alex Norman



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