yeah i have a good SSE-coded interpolating delay line kicking around which is why i think this is pretty easy. A smoothing technique for jumps is indeed one of the interesting problems but our line already does pretty well with a interpolate-at-1.5-speed traversal and stuff. backwards will be harder. I wonder if it will work!
you are kinda making me want to code it up and find out and leave it on a branch. LOL.