Median trilateral loop filter for depth map video coding

Emerging extensions to conventional stereo video technologies like 3D Video require to add depth information to 2D video data. This supplementary data needs to be coded efficiently and transmitted to the receiver where arbitrary viewpoints are generated by using this additional information. The depth maps are characterized by piecewise smooth regions, which are bounded by sharp edges describing depth discontinuities along object boundaries. Preserving these characteristics and especially depth discontinuities is a crucial requirement for depth map coding. When coding depth maps by means of a conventional hybrid video coder, ringing artifacts are introduced along the sharp edges and result in quality degradation when using the reconstructed depth maps for view synthesis. To reduce these ringing artifacts and also to better align object boundaries in video and depth data, a new in-loop filter is proposed, which reconstructs the described characteristics of depth maps.