Weighted-to-Spherically-Uniform SSIM Objective Quality Evaluation for Panoramic Video

As an important part of immersive media, panoramic video has entered the stage of commercialization in recent years. The panoramic video offers users an immersive viewing experience with its 360°horizontal and 180°vertical viewing angles. The spherical panoramic video has different projection relations in different regions of the sphere when projected to 2-D plane for encoding. In order to more accurately evaluate the objective quality of planar panoramic video and images, this paper proposes a method based on Weighted-to-Spherically-Uniform SSIM (WS-SSIM) to evaluate the objective quality of panoramic video and images. The structural similarity index (SSIM) is multiplied by different weights in different regions so that the spherical distortion observed by the user corresponds linearly to the plane distortion. The performance of the proposed WS-SSIM evaluation method is analyzed through experiments. The results show that the WS-SSIM evaluation method can effectively evaluate the objective quality of panoramic video and images.