[jitter] track and analysis

hello, 
i need to analyze a video input by detecting movement and also changes of black and white density...
i've tried few exemples patches and i come to the forum for more advices on the subject of live video input analysis.

i use jit.dx.grab for the live input and if i put the format at 640 480 the input image slows down...
any idea how i could render faster the live video in on my windows xp?

thanx for anyhelp

lochoi