DVD and *.flv playback is jerky on VLC

[AG <computing.account@googlemail.com>]

Hi

I've noticed, using Debian stable, that DVD and *.flv playback tends to 
be jerky.  That is, the motion of the actors, etc., seems to jump in 
short but noticeable ways, as if the playback is dropping several frames 
and picking it up again.  The sound track is fine, no jumps, but the 
movement on screen does seem to be a little jerky.  It doesn't seem to 
happen on other media players, or at least isn't as noticeable.

As a VLC novice, how do I address this? Any pointers for me to look at, 
and if so, what *should* I be paying attention to?

Many thanks for any steers.

AG