Project a portion of a movie file

Hello everybody!

My idea is to make a patch that takes a movie and
projects the change of a specific portion of that movie
in a new matrix.
A simple example here:

I have the following patch:

Verbally: I am grabing a 1 X 240 portion of the incoming movie,
and I project it on a new matrix. That last matrix is not cleared, but instead it is left to refresh its contents.

Now it looks like a scanline is updating the content in 1 X 240 pixel portions, reminds me of a photocopy machine. Definately
not what I want.

What I really want, is a way to make it appear as if it is moving in a continuous way, not like it
is refreshing (the "scan line" ).

I like to think of this last matrix as some form of circular buffer. Can this be done? Any suggestions on ways to do it?

Appreciate your help!