Flash Video with dots overlay

Hi everyone,
I have seen loads of cool sites with video that have an overlay of dots sitting over the video. I guess this is in part for a design aesthetic, and the other to reduce the visible amount of pixellation from the compression.
Can anyone tell me how to create this sort of effect dynamically, or am i going to have to duplicate a million movieclips? And if i do, will this affect performance?
Here is a reference to what I’m hoping to achieve:
http://www.noponies.com/dev/as3_fullscreen_bg_vid/
Thanks in advance,
J