Edge-aware coding tree unit hierarchical partitioning for quality scalable compression of depth maps

Abstract

The scalable extension of the high efficiency video coding standard (SHVC) combines the large compression efficiency and high visual quality of HEVC, with the possibility of encoding different versions of the same video in a single bitstream. However, this comes at the cost of high computational complexity. In this context, many research works aim to reduce this complexity for texture images. We aim at achieving the same objective, but for depth maps whose characteristics make them different from conventional texture images. Depth maps are indeed characterized by areas of smoothly varying grey levels separated by sharp discontinuities at object boundaries. Preserving these discontinuities is crucial to enable high quality of synthesized views at the receiver side. In this paper, we propose a fast depth maps encoding scheme for quality scalable HEVC while exploiting depth maps characteristics, SHVC Coding Unit (CU) depth information and the correlation between the Base Layer (BL) and the Enhancement Layers (ELs) of SHVC. If a CU corresponds to a depth smooth region, we maintain the same best coding depth of its co-located in the BL. If a CU is a sharp region, the best coding depth is computed in the same way as in the original SHVC. Experiments are conducted and satisfying results are obtained as the proposed method improves the SHVC coding speed without a significant impact on the synthesized views Rate-Distortion tradeoff