Although the archive of text generated by a persistent conversation (i.e. newsgroup, mailing list, recorded chat, etc.) is searchable, it is not very expressive of the underlying social patterns. In this paper we will discuss the design of graphical interfaces that reveal the social structure of the conversation by visualizing patterns such as bursts of activity, the arrival of new members, or the evolution of conversational topics. Our focus is on two projects: Chat Circles, a graphical interface for synchronous conversation and Loom, a visualization of threaded discussion. Through these examples we will explore key issues in the generation, design and use of graphical interfaces for persistent conversations. 1.

The analysis of 3D scenes consisting of nonrigid moving objects from 2D image sequences is discussed. A parametric description of dynamic objects is extracted and the time variant scene parameters are estimated throughout the sequence by employing an analysis by synthesis approach. From the parametric scene description images are synthesized and compared with the original input images of the camera. Frame differences between both images are evaluated to estimate a scene parameter update. The analysis system is applied to video phone scenes as a data compression algorithm where the scene parameters are transmitted and the output sequence is synthesized at the receiver. Index Terms -- 3D scene analysis, dynamic scene analysis, image sequence analysis, 3D motion estimation, 3D object tracking, 3D shape reconstruction, 3D shape adaptation, analysis by synthesis, object--oriented video phone coding. I. INTRODUCTION Modelling of 3D scenes from 2D image sequences has been a research topic for...

Automatic extraction of facial feature points is one of the main problems for semantic coding of videophone sequences at very low bit rates. In this contribution, an approach for estimation of the eye and mouth corner point positions is presented. For this proposition, the location informations of the face model are exploited to define search areas for estimation of the eye and mouth corner point positions. Then, the eye and mouth corner point positions are estimated based on a template matching technique with eye and mouth corner templates. Finally, in order to verify these estimated corner point positions, some geometric conditions between the corner point positions and the center point positions of the eyes and the mouth are exploited. The proposed algorithm has been applied to test sequences Claire and Miss America with a spatial resolution corresponding to CIF and a frame rate of 10 Hz. Keywords: Facial feature points, eye and mouth corner point positions, face model, template mat...