Optimization and Tracking of Polygon Vertices for Shape Coding

Abstract

The efficiency of shape coding is an important problem in low-bitrate object-based video compression. Lossy contour coding methods typically include contour approximation by polygons or splines, spatial and/or temporal prediction of vertices, and entropy coding the of prediction error. In conventional contour coding schemes, however, the coding gain in the interframe mode is typically small. This indicates that the temporal redundancy is not successfully removed. The paper addresses the issue of temporal shape decorrelation by proposing the Kalman filtering-based approach to vertex tracking and prediction. A temporal vertex association procedure is proposed effectively minimizing bit rate in each frame. The prediction error is coded using adaptive arithmetic encoding. Vertex optimization is employed to reduce the shape reconstruction error.