[mythtvnz] jumpy video

[Steven Mulvay]

Hi All, how are you?
I've finally got mythbuntu tuned up and running but the video is 
extremely jumpy, audio clips a little bit too, but nowhere near as bad 
as video.  Live TV and TV recordings are as bad as each other. 
My CPU shouldn't be drained very much because I'm using a PVR-150 which 
is a hardware MPEG-2 encoder. I am wondering whether Mythbuntu is 
having trouble using the encoder, although there are no errors shown on 
start-up. (I have splash turned off)
A guy on the myth-users  IRC channel says that there might be a PCI 
latency issue, but I am unsure how to test this. Altering the bitrate 
did not have any effect on the problem. The card works fine in Windows. 
Machine info: 
CPU: Intel 2 core duo
RAM: 4 Gig
Hard Drive: Approx 230 gig (virtually empty)
Kernal version: 2.6.24-19-generic
Mythbuntu version: Unsure, but I think it is the latest

Any help would be greatly appreciated.

Cheers,
Steve :)