Spherical Video Coding With Motion Vector Modulation to Account For Camera Motion Emerging immersive multimedia applications critically depend on efficient compression of spherical (360degree) videos. Current approaches project spherical video onto planes for coding with standard codecs, without accounting for the properties of spherical video, a severe suboptimality that motivates this work. A common type of spherical video is dominated by camera translation. We recently proposed a powerful motion compensation technique for such videos which builds on the observation that, with camera translation, stationary points are perceived as moving along geodesics that meet at the point where the camera translation vector intersects the sphere. However, the approach follows standard coding procedures and translates all pixels in a block by the same amount on their respective geodesics, which is suboptimal. This paper analyzes the appropriate rate of translation along geodesics and its dependence on the elevation of a pixel on the sphere with respect to the camera velocity pole. The analysis leads to a new approach that modulates the effective motion vectors within a block such that they perfectly capture the perceived individual motion of each pixel. Consistent gains in the experiments provide evidence for the efficacy of the proposed approach.

Reference Picture Synthesis for Video Sequences Captured with a Monocular Moving Camera Interframe prediction plays an important role in video coding by predicting the current frame from previously encoded pictures, called reference pictures. In the case of camera motion, the content of a current frame could be very different from its reference pictures and may consequently lead to a more difficult Motion Compensation (MC). The main idea of this paper is to process the input 2D video sequence in order to estimate the 3D geometry of the scene and then employ this data to virtually synthesize geometrically compensated reference pictures. Since these virtual reference pictures are more similar to the current frame, motion estimation and consequently coding efficiency could be enhanced. The proposed method is tested over six different video sequences and around 11% bitrate reduction is achieved compared to the High Efficiency Video Coding (HEVC) standard.