Improving view rendering quality and coding efficiency by suppressing compression artifacts in depth-image coding

We consider the effect of depth-image compression artifacts on the quality of virtual views rendered using neighboring views. Such view rendering processes are utilized in new video applications such as 3D television (3DTV) and free viewpoint video (FVV). We first analyze how compression artifacts in compressed depth-images result in distortions in rendered views. We show that the rendering position error is a monotonic function of the coding error. For the scenario in which cameras are arranged with parallel optical axes, we further demonstrate specific properties of rendering position error. Exploiting special characteristics of depth-images, namely smooth regions separated by sharp edges, we investigate a possible solution to suppress compression artifacts by encoding depth-images with a recently published sparsity-based in-loop de-artifacting filter. Simulation results show that applying such techniques not only provides significantly higher coding efficiency for depth-image coding, but, more importantly, also improves the quality of rendered views in terms of PSNR and subjective quality.