I try to get into CoreImage and sequence grabbing in order to do backgroud substraction from a iSight (or later even better) camera - thus detecting which part of the image is moving and which is stable. As this is not very far away from what you are doing, i tried to get your code to work, but i can't find it on your page, as some links to the source code seem to be broken, and getting it file-by-file through the Web-SVN interface did ot work. Could you post your actual code-tree again, please?