Improved near-lossless HEVC codec for depth map based on statistical analysis of residual data

A depth map represents three-dimensional (3D) data and is used for depth image-based rendering (DIBR) to synthesize virtual views. Since quality of the rendering view depends on that of the depth map, we should encode the depth map by maintaining the original quality. However, lossless depth coding requires a large amount of bits to carry the encoded depth map over the network. Thus, in this paper, we encode the depth map using high efficiency video coding (HEVC) near-lossless coding considering trade-off between the high quality and the bit saving. In addition, in order to improve the compression efficiency of HEVC near-lossless coding, we use large coefficients clipping and limited codeword lengh Golomb-Rice (GR) code, considering the statistical analysis of residual data. Experimental results show that the proposed method provides approximately 16.59% and 0.54% bit savings compared to HEVC lossless depth coding and HEVC near-lossless depth map coding, without the significant degradation of the synthesized view quality.