A new motion model for panoramic video coding

Virtual reality (VR) has been a hot topic in both research and industry, calling for more efficient compression of panoramic videos. Currently, panoramic video is played as if it is spherical, but such video is actually mapped to planar video, e.g. using equirectangular projection, before compression and transmission. The projection causes deformation and thus makes the traditional translational motion model not efficient. In this paper, we propose a new motion model based on spherical coordinates transform to compensate for the deformation in panoramic videos. Our model requires no additional motion vector but rather derives pixel-wise 2D motion vectors from a block-level 3D motion vector. Our experimental results show the significant bits saving achieved by the new model, which leads to as high as 8.0% BD-rate on the test sequences.