Three-dimensional motion vector translation for geometric partitioning mode in panoramic video coding using H.266/VVC

Geometric partitioning mode (GPM) is introduced into H.266/versatile video coding (VVC) as a new inter-frame prediction technology, in which one block can be divided into two non-rectangular blocks to increase partitioning precision of moving objects. In this paper, a three-dimensional (3D) motion vector (MV) translation based on spherical coordinate transformation is introduced into H.266/VVC and applied to GPM, in which the MV candidate list is constructed separately for each GPM partition. Firstly, the number of MVs in the GPM MV candidate list is expanded to 12, and all MVs in the merge mode candidate list are reserved, which can prevent the MVs with the best encoding performance from being removed. Secondly, the MVs of neighboring blocks of the current block are transformed by 3D MV translation and put into the blank positions of the newly constructed GPM partition MV candidate list. Thirdly, an independent motion compensation prediction based on the MV of each GPM partition is performed to improve the prediction accuracy. The experimental results demonstrated the effectiveness of the proposed method, achieving up to 0.44% reduction in BD rate in rate-distortion performance compared to H.266/VVC.