Improved motion compensation for 360° video projected to polytopes

360◦ video consists of images capturing the complete scene as seen from a single point in any direction. In contrast to conventional images, 360◦ images cannot be natively represented in a planar fashion. Consequently, video created from a sequence of 360◦ images suffers from geometric distortions. These are caused by mapping of the images from a sphere in 3D space to a planar image. This paper introduces an approach to improve motion compensation for 360◦ video by compensating the geometric distortions resulting from projection to the faces of a polytope. Each face is extended with content projected from faces connected to it. This provides better prediction candidates for motion compensation at face borders. Here, the applicability of the proposed method is demonstrated for 360◦ video projected to the faces of a cube. An evaluation of the method on two sets of sequences, static camera and non-static camera, verifies its effectiveness. It works especially well on non-static camera sequences, which have plenty of global motion. For the non-static camera sequences in the used test set rate savings of −2.14% were achieved.