Expansion hole filling in depth-image-based rendering using graph-based interpolation
Using texture and depth maps of a single reference viewpoint, depth-image-based rendering (DIBR) can synthesize a novel viewpoint image by translating texture pixels of the reference view to a virtual view, where synthesized pixel locations are derived from the associated depth pixel values. When the virtual viewpoint is located much closer to the 3D scene than the reference view (camera movement in the z-dimension), objects closer to the camera will increase in size in the virtual view faster than objects further away. A large increase in object size means that a patch of pixels sampled from an object surface in the reference view will be scattered to a larger spatial area, resulting in expansion holes. In this paper, we investigate the problem of identification and filling of expansion holes. We first propose a method based on depth histogram to identify missing or erroneously translated pixels as expansion holes. We then propose two techniques to fill in expansion holes with different computation complexity: i) linear interpolation, and ii) graph-based interpolation with a sparsity prior. Experimental results show that proper identification and filling of expansion holes can dramatically outperform inpainting procedure employed in VSRS 3.5 (up to 4.25dB).