A novel unbalanced multiple description scheme for video transmission over WLAN

Video communication over lossy packet networks such as the Internet or wireless links, is hampered by packet loss. Indeed, video quality severely degrades in presence of lost packets. This paper describes a technique based on Unbalanced Multiple Description Coding (UMD) to improve the robustness of video transmission. The proposed system relies on two descriptions, HR (High-Resolution) and LR (Low-Resolution) where LR description is primarily used as redundancy. HR and LR are produced by using different encoding parameters. The novelty of our approach, compared to other techniques based on UMD, is the use of different intra refresh periods for the produced descriptions. In particular we use shorter intra refresh period for LR description (in order to improve its resilience to bursts of packet losses), and higher intra refresh period for HR description (in order to improve coding efficiency). Moreover, a novel packetization scheme has been introduced in order to optimize network performance. This technique is able to produce acceptable quality even if redundancy percentage is less than packet loss rate. Therefore our UMD approach is suitable for multicast video distribution over WLAN (e.g. in "hotspots") where estimating packet loss can be a difficult task because different receivers experience different loss patterns.