Simple media-aware packet discard algorithms

IPTV solutions are emerging in the market today, both competing with traditional distribution mediums, such as cable TV, and creating new markets, such as mobile TV viewing using cellular networks. The distribution of IPTV is usually performed using a single stream, resorting multicast. This is not compatible with the growing number of devices which may be used to watch TV, from PDAs to laptops, desktops and high definition TVs, each with different processing and networking capacities. This has prompted research into scalable video coding and adaptation techniques, where a single video stream may be used for a large number of differentiated clients. In this paper we propose and evaluate two different metrics for IP packet discard by a media-aware network element, allowing it to reduce the bandwidth of an original video stream in case of congestion on a downstream link. The first metric consists in discarding the last IP packet of P frames. The second consists in discarding entire P frames. Through experimental evaluation, using subjective viewing scores, we conclude that both of our proposals allow for a much better viewing experience than random packet dropping, although quality still deteriorates rapidly as the drop rate increases.