Re: tvtime and the Linux 2.6 scheduler
From: Bill Davidsen
Date: Mon May 24 2004 - 14:37:15 EST
szonyi calin wrote:
--- Billy Biggs <vektor@xxxxxxxxxxxx> a écrit : > I am the
author of tvtime, a TV application with advanced
image
processing algorithms. Some users are complaining about poor
performance under Linux 2.6, and I would like more information
about how
tvtime will be treated by the scheduler. Here is an example
of the
intended usage:
- Program running as root and SCHED_FIFO
- NTSC, input ~30 fps, each field processed for an output of ~60 fps
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^
- CPU intensive processing, say 9 ms per field on my P3-733
- with a typical AGP card, the X driver takes 4 ms to draw
- Wait using /dev/rtc set to 1024 Hz
for(;;)
9 ms : process frame
4 ms : draw frame
3 ms : wait until next field time using /dev/rtc
9 ms : process frame
4 ms : draw frame
3 ms : block on /dev/video0 for next frame
-----
33 ms : time per NTSC frame
[___snip___]
For me it works ok
Running tvtime with 2.6.6-mm5 load average 26 (twenty six) it
works
almost perfect (no frame skipped -- at least not reported by
tvtime)
at full rate (50 frames/sec). Computer: AMD Duron 700 MHz, 256MB
~~~~~~~~~~~~~~~~^^^
Ram,
VIA KT133 chipset, AGP 4x, Ati Radeon 7200
There have been pretty good explanations of this, so I'll just say that
it might be that someone with a machine of limited capacity would be
able to generate 50fps and not 60fps. In much of Europe the TV flickers
at the same frequency as the lights ;-)
--
-bill davidsen (davidsen@xxxxxxx)
"The secret to procrastination is to put things off until the
last possible moment - but no longer" -me
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