Methods for depth-map filtering in view-plus-depth 3D video representation

Abstract

Abstract View-plus-depth is a scene representation format where each pixel of a color image or video frame is augmented by per-pixel depth represented as gray-scale image (map). In the representation, the quality of the depth map plays a crucial role as it determines the quality of the rendered views. Among the artifacts in the received depth map, the compression artifacts are usually most pronounced and considered most annoying. In this article, we study the problem of post-processing of depth maps degraded by improper estimation or by block-transform-based compression. A number of post-filtering methods are studied, modified and compared for their applicability to the task of depth map restoration and post-filtering. The methods range from simple and trivial Gaussian smoothing, to in-loop deblocking filter standardized in H.264 video coding standard, to more comprehensive methods which utilize structural and color information from the accompanying color image frame. The latter group contains our modification of the powerful local polynomial approximation, the popular bilateral filter, and an extension of it, originally suggested for depth super-resolution. We further modify this latter approach by developing an efficient implementation of it. We present experimental results demonstrating high-quality filtered depth maps and offering practitioners options for highest-quality or better efficiency.