[linux-audio-dev] Linux Security Module for realtime audio
Jens M Andreasen
jens.andreasen at chello.se
Wed Dec 10 09:05:05 EST 2003
On Wed, 2003-12-10 at 13:20, Paul Davis wrote:
> look, there are only 60-80 *physical* redraws of a monitor screen per
> second. you have, therefore, *at least* 1/100 of a second before
> you've "missed" a "graphics deadline". not only that, but because of
> the properties of the human visual system, missing the deadline won't
> matter in anything like the way missing an audio deadline does. this
> has none of the characteristics of "real time" from my perspective.
Updating 120 GTK+ sliders (as a consequence of a patch change) took
several seconds before I made the gtk thread SCHED_RR. I would call that
a missed visual deadline, No?
Notice that this sluggish behaviour is when the audio engine is near
idle, just writing silence to my ISA soundcard, which shows up as system
is using 5% cpu, user 0.1% cpu.
Now it takes a guesstimate of 0.3 seconds, perhaps a little less.
The kernel (and scheduler) is from the latest Mandrake 9.2 distribution
and I haven't yet found any notes on what patches they have applied this
> now, if the audio thread is burning so much CPU time that the GUI
> doesn't get to run, its certainly a problem. but step back - is it a
> problem you want to fix by raising the priority of the GUI thread so
> that it steals time from the audio thread?
No and the gui doesn't steal any noticeable time. I use something like:
gui_priority = audio_priority/20;
If I am maxing out the number of running voices then there will be
nearly no graphic updates at all (which is as it happens also the
cheers // Jens M Andreasen
More information about the linux-audio-dev