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

[Stroller]

On 11 Feb 2007, at 06:13, MythTV wrote:
> ...
> 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?

Probably none. A 5200 is used my many on this list & a 7600 should be  
powerful enough.

> 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?

It is likely that drivers are shipped with your distro. In Windows we  
are familiar with the "wizard" when new hardware is detected, but  
Linux does not bother with this. I think Linux simply does not bother  
storing information about what hardware was installed on the machine  
last time it booted, and when it starts it simply loads the  
appropriate drivers for whatever hardware it finds on the system  
(assuming it has them, either compiled statically into the kernel or  
in /lib/modules/$kernel_version, kind of an equivalent of C:\windows 
\system32).

I'm not familiar with you distro but it may well be that it ships  
with open-source drivers for the nVidia cards - nVidia's own binary  
drivers are MUCH better, but there may be licensing (or other) issues  
that prevent the distro from shipping with, or enabling, then by  
default.

The output of `lsmod` & `dmesg` may be informative, and you might  
wish to post these (or relevant sections) to the list. I use these  
`quotes` to indicate "type this at the command line of a terminal  
window".

> ... 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?

Well, it would certainly indicate that the issue is with performance  
scaling the video to full screen. You have successfully rules out  
(for instance) a bottleneck reading the video data off the hard-drive.

I am NOT an expert, however I'm inclined to feel that with such  
severe stuttering on a processor as well specified as yours the  
performance issue is related to _how_ you're doing the scaling rather  
than the raw CPU power. IE: there's something inefficient in the  
configuration of your software or drivers that's causing this overhead.

> 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?

This seems odd, and I'm inclined to this that it is worth pursuing to  
the root of the issue. Could it be that you're scaling TWICE when  
using the DVI to VGA adaptor?

You want to take a look at xorg.conf, the configuration of your X11  
display client, and its log files. These will likely be informative.

> 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?

Um... are you sure you don't mean XvMC?

 From <http://mythtv.org/docs/mythtv-HOWTO-3.html#ss3.1>:

   NOTE: It's strongly recommended that you use the proprietary NVIDIA
   drivers; they have excellent support for XvMC and ship with a good
   configuration utility. XvMC provides MPEG-2 hardware acceleration,
   which is important if you want to display HDTV.

> 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.

You have made quite an excellent request for help considering this.  
Have you come straight from Windows, or does your statement conceal  
experience with other unices? I am sorry that I'm not qualified to  
help further.

Stroller.