[mythtv-users] Questions about remote frontend...

Ray Olszewski ray at comarre.com
Fri Jul 11 12:16:12 EDT 2003


At 12:28 PM 7/11/2003 -0500, Calvin Gorriaran wrote:
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>Last night I setup my remote frontend. I figured that a 933mhz P3 w/ 768mb 
>ram would be plenty
>enough. I was getting a lot of jitters and CPU usage was up to 70%. This 
>is running across 100mbit
>ethernet connection and Xv is working. Running Redhat 9.0 w/ kernel 2.4.21 
>and latest CVS of mythtv.
>Any suggestions on what I could do to locate the bottleneck?

This CPU usage certainly seems very high, even for what by today's 
standards is a low-grade frontend. Here are some thoughts.

1. If you can (if your X setup permits, that is), switch to a different 
desktop, so the Myth display is not actually visible at all (But playback 
is still running). See if that reduces CPU use dramatically. If it does, 
you have an XV problem of some sort (no matter what you think told you that 
"Xv is working").

2. Also check what actual processes are using CPU, and what the split is 
between kernel and user processes. This will help you (or if not you, us) 
spot whether the problem is in Myth or X.

3. What encoding are you using? What capture size (HxV)? NTSC or PAL?

4. What are "jitters"? Is it different from "choppy" (someone else's 
problem yesteday, which I read to mean there are skipped frames)? I think 
of "jitters" as meaning that the image is somehow bouncy, as though the 
camera were not being held steady. But you may mean something different ... 
we really need to agree on some terminology for describing video problems 
(I am too inexpert to make suggestions, but perhaps someone else on the 
list is sufficiently knowledgeable to help here?).

5. What NIC are you using? This is a longshot, but I seem tor ecall that 
some NIC drivers (e.g., rtl8139) make fairly large demands on CPU (in 
contrast to, say, tulip or the various 3c* drivers).

6. Is *anything* else actually displaying on the screen besides the Myth 
playback? If yes, might it be causing context switches that burn CPU?

Aside from that, if you post a followup, please include the usual details 
about your hardware and X.





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