Re: Upcoming Qt switch to OpenGL ES on arm64
On Monday 26 November 2018 16:16:40 Alan Corey wrote:
> I think not pulling it to full screen puts everybody in the same boat
> by using the default size.
It also hands you figures not achievable in the real world, often off by
20x.
> But I can watch videos with smplayer on my
> Rock64, on a Pi I need to use omxplayer because smplayer is too low.
> There was some mention on the pine64.org page about using the Rock64
> as a multimedia machine.
Seems so, sadly.
> Ah, does linuxcrc do any kind of video acceleration? Never seen it.
> It could with DRI I think.
No, its gui is pretty simple, depending only on a basic x server thats
fast enough to keep up with the machines movements. The rpi3b fails that
speed rather spectacularly with its frame buffer video.
I could post a screen snapshot but I believe the listserver strips them.
DRI is generally fast enough on the intel atom powered boxes, and their
irq response it outstanding. Unforch the good intel board, the D525MW
was discoed 5 years ago and the supply lines drained rapidly.
Where its super critical is in the response time and consistency of that
time, to a scheduled interrupt, which may be at 25 microsecond intervals
if you are driveing stepper motors in software. If that 25 u-second time
wobbles by 5 u-secs, it can play hob with a stepper motors available
torque.
Many of us use fpga cards to offload that from the computer, but they
also add from $120 to $300 to the cost of building a usable machine.
Getting that stepper drive job off the cpu means the rest of it can be
done in a 1 millisecond thread, and some of what I am doing on a big
lathe can be done in a 200 hz thread, which is how I move the machine
manually since the CNC replaces any hand cranks the machine may have had
when it was new, some of them up to 100 years old, with encoder dials
such as the $20 one from mpja.com. I use 2 of them on that 70 yo
Sheldon. Works nice, to an accuracy of .0001". And I can electronicly
adjust the per click distance up to twenty thou per click, which can
drive the machine faster than it can move if I spin the knob fast.
So 2 requirements, if satisfied, lets these little credit card computers
run LinuxCNC well.
1. rt-preempt (or full rtai) patched kernel. Usually pinned to keep apt
from installing a newer kernel that is NOT suitably patched.
2. A usable speed SPI interface, which the pi is outstanding at, I am
writing 32 bit packets to that interface card at 42 megabaud, and
receiving its replies at 25 megabaud. Whether that can be done on the
rock64's I have remains to be seen. The driver that does that is
rpspi.ko, and its written specifically for the pi3b. Part of the LCNC
install these days.
3. usable real world video speeds, 20 fps or more for full screen
refresh.
4. We don't care about audio, we probably wouldn't hear it over the noise
of the machine anyway. :-)
Thanks Alan.
--
Cheers, Gene Heskett
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>
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