Abstract
In video conference systems over the Internet, audio and video data are often lost due to UDP packet losses, resulting in QoS degradation. In this paper we describe a high-assurance video conference system that improves the quality of audio and video data. Two techniques were used: (1) packet loss recovery using convolutional codes, which improves the dependability of communication; and (2) Xcast, a multicast that is designed for relatively small groups, reducing the bandwidth required for a multi-point conference. We added these functions to a Gatekeeper(GK), a device used in conventional conference systems. Encoding/decoding and Xcast routing were then implemented as the upper layer for the UDP. We investigated the effectiveness of the proposed system in experiments using an Internet simulator. We also examined the functions of the system over the Internet in a multi-point conference between Internet domains metro-u.ac.jp and toritsudai.jp.