t@b ZS4 is a video compositing/editing system with more than 120 built-in video effects including excellent color and chroma keying. Other features include custom output video width and height, unlimited tracks and sub-composites, custom speed and direction change for video and audio, and the ability to slave effect and compositing controls to audio wave forms. ZS4 is free for personal use. Visit http://www.zs4.net.