Audio/Video Problems

[Gene Heskett]

On Thursday 03 January 2013 12:28:48 Myriam Schweingruber did opine:
Message additions Copyright Thursday 03 January 2013 by Gene Heskett

> On Thu, Jan 3, 2013 at 1:42 PM, Mark Greenwood <fatgerman at gmail.com> 
wrote:
> > On 3 Jan 2013, at 12:20, Bill vance wrote:
> >> Howdy folks;
> >> 
> >> I'm running a fresh install of Kubuntu 10.04 on an i386 machine, and
> >> have downloaded most
> >> of the Medibuntu progs, and I'm still experiencing some wierd
> >> audio/video problems.
> 
> Just as a basic information: it makes little sense to do fresh
> installations of 10.04 that will reach it's End of Life in less than 4
> months, when you have a more recent LTS version available....
> 
> 
> Regards, Myriam

For some uses Myriam, such as running industrial machinery, the more recent 
releases have not been capable of doing that.  LinuxCNC is one of those 
apps.  We are making progress at building a kernel with the IRQ response 
time such real world controls need.  For 10.04, we were able to build a 
single kernel with the RTAI patches, but those patches have not applied 
cleanly, or performed well on the later kernels, and the author, Paolo M. 
has fallen somewhat behind.  The xenomi seems also to be capable of what we 
need to do this successfully, and I expect we will have a working, 
downloadable cd available by the time the 10.04 LTS actually expires.

The Intel atom boards such as the D525MW have set the gold standard for us 
for the last 2 years, giving us the ability to issue commands to the 
hardware at timing cycles below 25 u-secs, with a timing accuracy if 7 u-
secs worse case, and 2.5 u-secs accuracy for hours at a time.  This is not 
a particularly powerful board, dual core 1.6Ghz.

We as a group, are a niche group of course, but from activity on our IRC 
channels and mailing lists, I would hazard a guess that the 1 or 2 hundred 
of us there were when we switched to Ubuntu as a basic install at 6.06 LTS, 
is now a considerably larger count, planet-wide 2 to 3 thousand.  That's 
just the guys that have time to contribute to the mailing list.

We have no clue how many installs Toyota has, but there is at least a 
chance that if you are driving a serious TRO model with the big alu V8 in 
it, that LinuxCNC did the finish machining of your engine block.  It is 
capable of doing co-ordinated motion controls on a 9 axis machine, and was 
at one time considered munitions with stringent export controls because it 
could carve the compound curves that gave quiet submarine screws.

I guess what I wanted to say was that for some uses, the latest and 
greatest, because its real world performance sucks dead toads thru soda 
straws, is a disaster.  You simply cannot move a machine capable of moving 
a flood cooled cutting tool spinning 20k rpms through alu or steel in terms 
of meters per minute, without being able to sample its position, do the 
math and issue corrective orders at millisecond or faster rates for servo 
controls, or to stepper motors at a minimum of 40,000/sec with software 
step generation.  External stepper generators can take that maximum rate to 
over a megacycle, but then of coarse its no longer a 100% LinuxCNC 
solution, needing additional hardware that can run $1000/axis controlled.

Cheers, Gene
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