Perhaps you can use the source of your video (syphon, jit.qt.movie, etc.) to limit the size of your frame or number of frames/sec that it is outputting. STart there so you don’t have to cascade further into the patch.
AFter limiting there first, then you can additionally limit by slowing the # of messages with objects like qlim.
And you can downsample matrices of your data using objects like jit.matrix, Look at the jitter tutorials for lots of ideas on these topics. For example tutorial 14.