Packet Loss Recovery for Unicast

Srinath R. Joshi. Packet Loss Recovery for Unicast Interactive Video Transmission over the Internet. (Under the direction of Professor Injong Rhee.) The current Internet is not reliable; packet loss rates are frequently high, and varying over time. Transmitting high-quality interactive video over the Internet is challenging because the quality of compressed video is very susceptible to packet losses. Loss of packets belonging to a video frame manifests itself not only in the reduced quality of that frame but also in the propagation of that distortion to successive frames. This error propagation problem is inherent in many motion-based video codecs due to the interdependence of encoded video frames. Recently a new approach to improving error resilience of compressed video, called Recovery from Error Spread using Continuous Updates(RESCU), has been proposed. In RESCU, picture coding patterns can be adjusted to enable the use of transport level recovery schemes in recovering lost packets without having to introduce any playout delay at the receiving end. In this thesis, we propose dynamic loss recovery schemes which when combined with RESCU, e ectively alleviate error propagation in the transmission of interactive video. In these schemes, picture coding patterns are dynamically adapted to current network conditions in order to maximize the e ectiveness of hybrid transport level recovery (employing both forward error correction and retransmission) in reducing error propagation. Through an experimental study based on actual Internet transmission traces representing various network conditions, we study the e ectiveness and limitations of our proposed techniques and compare their performance with that of existing video error recovery techniques such as Intra-H.261 and H.263+(NEWPRED). Our study indicates that the proposed techniques exhibit better error resilience and incur much less bit overhead than existing video error recovery techniques. This document also describes the implementation of a prototype interactive video transmission system employing a proposed loss recovery scheme. Packet Loss Recovery for Unicast Interactive Video Transmission over the Internet