Jerky Video Playback For An Ubuntu Beginner

[James Bensley]

Hey List,

I have a Karmic Koala (9.10) box (x86) running with 2GBs of RAM and a
2.0Ghz Core2. I am having difficulties watching videos in Linux that
play OK in Windows. The machine is dual boot with Windows XP
Professional x64 SP3.

In windows I have the nVidia drivers installed, a fully up-to-date OS
and Direct X 9.0c and I can watch most HD films OK except stuff that
is of a rather high bit-rate (above 24Mbps and it starts to jerk a lot
but the card is currently in a x8 PCIE slot, I'm going to move it to a
x16 when I get a chance).

In Ubuntu I am fully up-to-date with the OS, I installed the latest
nVidia drivers today (190.53, before I was on something like 183 (by
following these instructions
http://ubuntuforums.org/showthread.php?t=57368)) and I am having the
same issues as before I updated the drivers (I was hoping this was the
problem). In Ubuntu video plays but it is clearly slower, lines appear
across the screen where parts of it aren't updating quickly enough
(that's the only way I can describe it).

In windows when watching a film at 24Mbps, 1080i I have about 70% CPU
usage across both cores. From Ubuntu I have 40% on the first and 80%
on the second. In each case the CPU usage is consistent through the
watching of the film. So its higher in Windows and the playback is
smoother. Maybe Ubuntu off-loads more of the work onto the GPU and
this is why playback isn't as clear. Or maybe it just isn't pulling
its wait with the CPU and that is why it isn't as clear?

My graphics card is a GeForce GT 240 in an x8 PCIE slot and when I get
a chance I will move it to a x16 slot. But for the time being I would
expect the same results in Ubuntu as in Linux.

Side note: Windows runs off a single hard drive but Ubuntu is on a
RAID 5 so we can rule Ubuntu out as having slow data access ;)

Sorry for the long post; any help is greatly appreciated.
-- 
Regards,
James ;)