Christian Huitema

Videoconferencing on the Internet

This paper describes the INRIA videoconferencing system (IVS), a low bandwidth tool for real-time video between workstations on the Internet using UDP datagrams and the IP multicast extension. The video coder-decoder (codec) is a software implementation of the ITU-T recommendation H.261 originally developed for the integrated services digital network (ISDN). Our focus is on adapting this codec for the Internet environment. We propose a packetization scheme, an error control scheme and an output rate control scheme that adapts the image coding process based on network conditions. This work shows that it is possible to maintain videoconferences with reasonable quality across packet-switched networks without requiring special support from the network such as resource reservation or admission control.

Minimal complexity for the simplest protocol

The design issues of a multimedia transport protocol, TP5, which achieves the multiplexing of both real time and normal data flows at the transport layer are discussed. The use of a single transport connection to carry both data flows is proposed. Two schemes for the support of the synchronization of these data flows are presented. The protocol TP5 implementing the above mechanisms is described. It is shown that with the use of the described synchronization schemes, the TP5 protocol minimizes the control of the real time traffic while still controlling the normal data flow.<<ETX>>