Adaptive forward error correction for real-time Internet video

Real-time video communication over packet networks is attracting increasingly more attention for applications such as distributed collaborative work, teleteaching and telemedicine. Due to its sensitivity to delay, real-time communication is usually based on unreliable transport protocols, like UDP, since retransmission of lost packets is considered to take too long time. Instead of retransmissions forward error correction schemes have been proposed to make the applications more resilient to packet loss. Since the packet loss rate on the Internet typically fluctuates depending on the load of the network, the amount of redundancy applied by the error correction coding should ideally be adaptive to the amount of loss experienced on an end-to-end connection. In this paper an adaptive forward error correction scheme, based on Reed-Solomon erasure coding and receiver feedback, is presented. Moreover, an optimal packetization strategy for error protected video communication is suggested and an efficient algorithm implementing this packetization scheme is deduced. The performance gain of the scheme, in terms of increased network bandwidth utilization, is analyzed and found to be as high as around 10 % for some relevant usage situations. The combination of adaptive forward error correction schemes with congestion control algorithms is also discussed in the paper. 1