Packet Forth (PF) is a scripting language for real-time video processing and graphics generation. PF is now quite stable and usable, but remains a bit of an odd duck in the land of open source video processing tools. I use it mainly as a prototyping tool for C-based signal processing.
PF is a concatenative programming language which takes ideas from Forth, Joy, PostScript, Factor, and Lisp. As opposed to its memetic parents, PF is not intended as a general purpose programming language, but a scripting language that glues together black box processing primitives and relevant open source libraries