WRITE-CHAT: A Brief Description


The write-chat software is developed as a hand-writing based chat software to communicate over the Internet.  The main feature of this software is that equations or graphs can be drawn on an ordinary piece of paper (or a blackboard) and a web-camera based system captures and transmits the background view over the Internet. The foreground consists of hand and pen (or the instructor, if a blackboard is used for discussions) and the background consists of hand-writings. In this particular case the background and the associated audio carries the useful information. That is why the background video instead of the foreground video is transmitted. This concept is independently investigated by researchers from Microsoft Research Why take notes? Use the Whiteboard Capture System, by Li-wei He, Zicheng Liu, Zhengyou Zhang presented at IEEE ICASSP 2003 and a related paper was presented at IEEE ICASSP in 2004.


The background is recursively estimated using an IIR filter from captured video frames using the method developed by Kanade and his coworkers.  The main advantage of using background is encoding efficiency because the background image is smoother than actual image frames of the video and the encoder does not try to compress the instructor or the hand, which do no carry any information. 


A one-bit per pixel version of the software is also developed for very low bit Internet channels.  This is another advantage of the background based transmission because the background image can be quantized to one-bit without causing disturbing effects and without loosing any useful information. Since the images of the blackboard (the notepad) are binary in nature consisting of writings and drawings on the board (the paper).


The software is tested between Cyprus and Turkey, and is intended to be used to communicate between ENST, Paris and Bilkent University this summer in the MUSCLE framework.