A Generalized Cubemap for Encoding 360° VR Videos using Polynomial Approximation. (14th November 2019)

• Record Type: Journal Article
• Authors: Xiao, J. Y.; Tang, J.T.; Zhang, X. Y.
• Is Part Of: Computer graphics forum. Volume 38:Number 7(2019)
• Page Start: 359
• Page End: 367
• Publication Date: 2019-11-14
• Subjects: CCS Concepts -- Human‐centered computing → Virtual reality -- Computing methodologies → Virtual reality; Image representations; Computer graphics -- Periodicals; 006.605
• DOI: 10.1111/cgf.13843
• Languages: English
• ISSNs: 0167-7055

Abstract

Abstract: 360 ° VR videos provide users with an immersive visual experience. To encode 360 ° VR videos, spherical pixels must be mapped onto a two‐dimensional domain to take advantage of the existing video encoding and storage standards. In VR industry, standard cubemap projection is the most widely used projection method for encoding 360 ° VR videos. However, it exhibits pixel density variation at different regions due to projection distortion. We present a generalized algorithm to improve the efficiency of cubemap projection using polynomial approximation. In our algorithm, standard cubemap projection can be regarded as a special form with 1st‐order polynomial. Our experiments show that the generalized cubemap projection can significantly reduce the projection distortion using higher order polynomials. As a result, pixel distribution can be well balanced in the resulting 360 ° VR videos. We use PSNR, S‐PSNR and CPP‐PSNR to evaluate the visual quality and the experimental results demonstrate promising performance improvement against standard cubemap projection and Google's equi‐angular cubemap.