Spline-based boundary loss concealment

Object-based video coding requires the transmission of the object shape. This shape is sent as a binary alpha-plane. In lossy packet-based networks, such as the Internet, this information has a non-negligible probability of not arriving at the receiver, and hence its loss needs to be concealed. In this paper we propose a shape concealment technique utilizing Hermite splines. The algorithm has the following steps: (I) the received boundary is detected and the lost boundary parts are grouped using the packet loss pattern. (II) for each of these lost boundary parts, the received boundary points that border the area of the lost boundary parts are collected. These boundary points are then modelled by a second order Hermite spline. This model is subsequently used to match the velocity along the received boundary with the velocity of the concealing cubic Hermite spline. (III) since in most cases there are more than one concealing splines we draw every spline combination that does not result in an intersection and keep all possible results until the end. (IV) if there are more than one possible solutions we select the one that results in one overall closed non-intersecting boundary and fill the interior of the boundary to get the concealed alpha-plane. Experimental results which demonstrate and compare the performance of the proposed concealment method are given at the end of the paper.