Depth Intra Coding for 3D Video based on Geometric Primitives

This paper presents an advanced depth intra coding approach for 3D video coding based on the high efficiency video coding (HEVC) standard and the multiview video plus depth (MVD) representation. The work is motivated by the fact that depth signals have specific characteristics that differ from natural, i.e., camera-view video. Our approach replaces conventional intra-picture coding for the depth component, targeting a consistent and efficient support of 3D video applications that either utilize depth maps or polygon meshes or both, with a high depth coding efficiency in terms of minimal artifacts in rendered views and meshes with a minimal number of triangles for a given bit rate. For this purpose we introduce intra-picture prediction modes based on geometric primitives along with a residual coding method in the spatial domain, substituting conventional intra prediction modes and transform coding, respectively. The results show that our solution achieves the same quality of rendered or synthesized views with about the same bit rate than MVD coding with the 3D video extension of HEVC (3D-HEVC) for high quality depth maps and with about 8% less overall bit rate than 3D-HEVC without related depth tools. At the same time the combination of 3D video with 3D computer graphics content is substantially simplified, as the geometry-based depth intra signals can be represented as a surface mesh with about 85% less triangles, generated directly in the decoding process as an alternative decoder output.