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Parallel-to-Axis Uniform Cubemap Projection for Omnidirectional Video

Omnidirectional video can provide an immersive visual experience by presenting a 360° video content. For omnidirectional video, pixels on the sphere need to be mapped onto a two-dimensional plane to adapt to the existing coding standards. Equirectangular Projection (ERP) and Cubemap Projection (CMP) have excessive sampling density on some sampling regions, which results in unnecessary sampling pixels. In this paper, Parallel-to-Axis Uniform Cubemap Projection (PAU) is proposed. After projecting the sphere to a cube like CMP, an equal-angle mapping position adjustment is used to sample the sphere more uniformly. After adjustment, one chosen axis is equal-angle sampled and each line parallel to the other axis is sampled equiangularly in the proposed format. Experimental results show that our proposed projection format can achieve 10.68% bitrate gain compared to ERP.