"vvvv is a toolkit for real time video synthesis. It is designed to facilitate the handling of large media environments with physical interfaces, real-time motion graphics, audio and video that can interact with many users simultaneously.
vvvv uses a visual programming interface. Therefore it provides a graphical programming language for easy prototyping and development.
vvvv is real time. where many other languages have distinct modes for building and running programs, vvvv only has one mode - runtime.
vvvv is free for non-commercial use. Commercial use requires a license. Get the latest version from the Download section.
vvvv is being developed by the vvvv group."
Notes: PC only. Interesting examples of use @ vvvv on Vimeo
"interactive multi touch cocktail bar. video tracking using infrared light. software is vvvv."