How to pipe Y' values as array per frame?

[Jonathan Chetwynd]

Is there a simple way to pipe an array of Y' values for each frame**?

apologies if the question is poorly phrased, hope the intention is clear,

my C is naive and the sdk tutorials lengthy and not clearly designed to 
meet my needs ))

kind regards

Jonathan

** ie whilst wfm:
gst-launch -e v4l2src device=/dev/video0 ! 
'video/x-raw-yuv,width=320,height=240,framerate=60/1' ! xvimagesink
what I would like is the raw Y' values.

-- 
Jonathan Chetwynd
http://www.gnote.org
Eyetracking in HTML5