[mythtv-users] Not enough processing power causing HD video to stutter or jitter?

[MythTV]

I built a MythTV system from the ground up with the intention of it  
handling ATSC HD streams in Dallas, Tx.  My hardware configuration is:
CPU: Intel Pentium 4 CPU 3.2GHz Socket 775 800 FSB w/Hyper Threading  
Technology
Memory: 512MB DDR 333 Memory 180 Pin (Major Brand)
Motherboard: ASRock 775i65G Mother Board
Optical Drive: LG 18X DVD RW + Dual Layer
Hard Drive: Western Digital 160GB 7200RPM 8MB Cache Serial ATA
Video onboard: Integrated SiS Ultra256 2D/3D Graphics
Video card: GeForce FX 5200 with 128 MB
Audio onboard: AUDIO ADI AD1888 6-channel audio CODEC
Audio card: Riviera C-Media CMI 8738 (I intend to connect optical out  
to entertainment center)
Network Card: Onboard 10/100 Network Card
Tuner card: pcHDTV HD-5500

My research prior to purchasing the equipment told me that this  
system would have the horsepower to be a backend and frontend  
system.  When I look at other people's configurations for an HD  
system, my system is comparable or better.  Here are my hardware  
configuration sources:
http://www.linuxis.us/linux/media/howto/linux-htpc/ 
determining_your_needs.html
http://www.wilsonet.com/mythtv/printer-friendly.php? 
SID&expandables=closed&ivtv=closed&pvr350out=closed#hw
http://pvrhw.goldfish.org/tiki-pvrhwdb.php

The only configuration that I can't confirm is whether or not I got a  
computer with 800 MHz Front Side Bus; how can I determine the speed  
of my FSB?

Now, down to the problem --
The problem is that my video is consistently jittering.  When I  
"Watch TV" on a low bandwidth channel, the video seems fine.  When I  
"Watch TV" on a high definition station, the video seems like slow  
motion for about 3 seconds, then a jump in the video occurs, and then  
it goes back to slow motion again.  On non-action streams, like the  
news, this is the typical sequence of events.

When there is a big scene transition or lots of action, the whole  
video freaks out (my term for a full screen of artifacts) for a  
moment (noticeable that every other line is drawn, better but still  
unacceptable when deinterlace is on) before returning to the 3 sec...  
video jump... cycle.

I originally installed KnoppMyth and that's when the problem first  
showed up.  I like trimmed down OSes but the KnoppMyth environment is  
so trim that it makes it hard to troubleshoot.  Therefore, I clean  
installed MythTV on Fedora Core 6 following Jaron's weblog.  After  
many hours of work (but a better computing environment,) I found that  
I had the same 3 sec...  video jump... cycle.  The problem is not as  
pronounced on Fedora as it was on Knopp, but still unacceptable.

Now, all the questions --
My video card is the GeForce FX 5200 with DVI and S-video out.   
Changing video cards does not seem to make ANY difference.  I have  
tried a 7600 and some $300+ nVidia card.  What kind of results should  
I see with a video card change?

I have not been able to figure out how to get the 5200 video software  
installed.  However, Fedora seems to recognize the card under System- 
 >Administration->Hardware saying "nVidia Corporation NV34 [GeForce  
FX 5200]".  Does this mean that I don't have to install any video  
software?

I installed xine to compare playbacks.  Xine has the exact same  
problem.  HOWEVER, when I set video to 100%, the problem almost  
completely goes away.  Video playback is acceptable except that I  
only see about 20% of the screen on my VGA monitor.  Would this mean  
a have a processor power issue?  Why would I have processor power  
issues when other MythTV HD setups do with less?  Is my only option  
to buy a more powerful computer?  And if so, then how much power do I  
need?

I've been running my build environment with a DVI to VGA adaptor.   
VGA forces the video to 800x600 where DVI can handle up to 1680x1050  
(I think.)  I originally wondered whether the VGA adaptor  
requirements were causing some of the issues.  So I got a DVI monitor  
and tested at 1344x840 and 1680x1050.  The problem still occurred.   
In xine at 100%, I could almost see the whole video stream without  
any noticeable slow motion; however, very slight video jumps still  
occurred.  Does VGA resolution require more computation power than DVI?

Because I haven't installed the video software, I questioned whether  
Xvid was running on the video card.  Everyone says Xvid should be  
turned on for better MPEG performance, but I can't find a web site to  
tell me how to turn it on.  Can someone point the way for me?

When I use xine-check, I get a status of "good" on all settings but:
[ hint ] No xine-config found. Assuming xine from RPMs
[OUCH!!] There are no inputs plugins.
[OUCH!!] There are no demux plugins.
[OUCH!!] There are no decode plugins.
[OUCH!!] There are no video_out plugins.
[OUCH!!] There are no audio_out plugins.
The xine-check OUCH error suggests that I reinstall xine-lib; "yum -y  
install xine-lib" says that there's nothing more to be installed.   
How do I [or do I need to] install the missing plugins mentioned above?

xine-check does report a "good" on "your Xv extension supports YV12  
overlays (improves MPEG performance)" and "Xv ports: YUY2 YV12 UYVY  
I420 YUY2 YV12
UYVY I420".  Does this "good" mean that Xvid is running properly on  
my video card?

I am only 30 hours new to linux so if you choose to help me, please  
provide details about how and where to get/install stuff.  Thanks!

Rob