[PD] converting video patches from jitter

hello,

i need some advise about a video processing lib i could use to
convert some c'74 jitter patches. basically, the patches need to be
running smooth on a medium speed computer, the libs should be free
and open source and running on both linux and mac (intel). the stuff
done in jitter is pretty basic and currently uses these objects:

jit.qt.movie streaming movie files off harddisc ; note that the
movies can be converted to any other movie format if necessary jit.matrix storing frames jit.window presenting movies jit.scalebias modifying r / g / b dynamics jit.op applying fadings jit.alphablend superimposing png images with transparency jit.rgb2hsl and jit.hsl2rgb animating de-saturation (to greyscale)
and back to colour

as far as know, when using PD, there are these possibilities:

GEM will allow me to play video files as openGL textures but not be
doing matrix-pixel stuff? framestein windows only? gridflow looks as if this has a concept similar to jitter? says mac
version is "experimental" ... pdp also looks like jitter, but more macro objects instead of low
level when comparing to gridflow? says its linux + mac

also jitter already chokes with playing four small movies (cpu- nonintensive codec!!) on a fast macbook, so i hope to also reduce the
"jitter" in the frame rate timing (images are only 12 fps but jitter
seems to be really bad in keeping proper timing). to me it looks if
either gridflow or pdp could be a good choice?

thanks for hints (also if there is something i could use outside pd,
i'm gratefull for infos)! ciao,

-sciss-