Subject: Re: [linux-audio-dev] an open letter to Linus re: low latency
From: Benno Senoner (sbenno_AT_gardena.net)
Date: Mon Jun 26 2000 - 01:46:20 EEST
On Sun, 25 Jun 2000, Jay Ts wrote:
> David Olofson wrote:
> > Reliable real time scheduling is absolutely essential for industrial
> > control systems
>
> In general, robotics. (Sorry to interrupt... :)
note that LL can't cover ALL industrial control system/robotics needs:
there are fields where 1-2ms are adequate , others require 20-50usec
and here you have to use RTLinux , QNX , or some other true RTOS.
But for multimedia, a fully pre-emptive kernel is just overkill.
Indeed: if LL is able to do rock-solid audio, it will apply to video too,
since video framerates are at 50-100Hz which means 10-20msec
per frame.
That is much higher than the 2.1ms audio latency I achieved on the
P133.
:-)
>
> > and some kinds of multimedia applications, and
> > improves the quality of games and most kinds of multimedia. Since
> > multimedia and in particular, games, is what most desktop systems are
> > used for these days, it's strategically important to provide
> > competitive performance in this area.
>
> Well put. I suggest that something very similar to this be added
> to the letter to Linus, with emphasis on "absolutely essential".
> The LL patch isn't just for us audio people.
Yes, and it's amazing that no one (except Ingo) cared about keeping worst-case
latencies down.
But since opensource is an evolutionary process, Linux in order succeed on
the desktop, will have to provide these features, or no one will be motivated
to switch.
The pressure will come not only from linux-audio folks, but other areas too.
( as said gfx, embedded etc)
I mailed with Bruce Johnson of SGI (he is one of the realtime folks), and
he told me SGI is interested in dropoutfree, high framerate realtime rendering
on Linux (virtual reality comes to mind), therefore lowlatency seems the best
way to go.
I think vendors or distro manufacturers will ship these features eventually
in their packages in the case that Linus will refuse to include LL into the
mainstream kernel.
Benno.
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