A video communications testbed for transmission over paeket switching networks

Abstract

Over the last decade, video coding and networking technology have both advanced significantly. We now have standardized low bit rate video compression codes such as CCITT H.261, and also have low cost network access such as Ethernet, frame-relay, and switched megabit data service (SMDS). To facilitate research for cost-effective video communications over packet switching networks, this paper describes a real time testbed and illustrates some results. In packet switching, video packets can be lost or have random. delay. If a compression code is sensitive to packet loss or random delay, the end-to-end video transmission quality can be unacceptable even at a moderate network utilization. We will demonstrate some real time transmission results over Ethernet. To help developing a good compression code, we need to identify the performance dependence of video transmission on various network transport conditions. To achieve this, a network emulator is used in the testbed. The network emulator can support high speed transmission and can be programmed for different network conditions such as random delay. With the help of the emulator, we can evaluate video quality in real time and develop compression codes for transmission in different networks.