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SubjectRe: tvtime and the Linux 2.6 scheduler
Date
szonyi calin wrote:
> --- Billy Biggs <vektor@dumbterm.net> 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@tmr.com)
"The secret to procrastination is to put things off until the
last possible moment - but no longer" -me
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