Shape adaptive padding for MPEG-4

In MPEG-4, the boundary blocks of reference video objects are padded by replicating the boundary samples towards the exterior. This scheme does not make use of the trend of pixel value variation often present near object boundaries in padding the exterior pixels of the reference video object. Rather, it results in a break of this trend at the video object boundary, resulting in higher prediction errors for those pixel locations that are within the shape of the current block, but are outside that of the predicted block. In this paper, we propose a novel shape distortion adaptive hybrid padding technique to minimise prediction errors and improve compression efficiency. We show that this technique results in boundary block coding gains of up to 9% as compared to that of the MPEG-4 scheme.