PDP is an extension library for Pure Data, providing video and other media processing functionality. PDP's focus is on images and video, but there is support for matrix processing, 1D and 2D binary cellular automata and opengl rendering (like Gem). PDP runs on Linux and OSX. The OSX version depends on Fink.
For more image processing objects, streaming objects and a collection of very useful additions to the bare bones PDP functionality, have a look at Yves Degoyon's PiDiP library.
For documentation, have a look at the 'pdp' subdirectory in pd's 'Pure
Documentation'. Most objects are documented with pd style help
patches accessible by right clicking on an object. The place to send
questions is the Pure Data mailing list.
The latest stable PDP tarball release can be found in the
section of the Pure
pd-pdp package is currently maintained
by Paul Brossier. PDP is written by Tom
Schouten and released under the GPL v2.