A reduced computational effort mode-level scheme for 3D-HEVC depth maps intra-frame prediction

To encode the depth maps efficiently, 3D-HEVC introduced three intra-frame prediction tools: (i) Depth Intra Skip (DIS), (ii) Depth Modeling Modes (DMMs), and (iii) Segment-wise DC Coding (SDC) that raise the encoding effort. Therefore, we analyzed the most time-consuming steps at the intra-frame prediction and proposed a model-level scheme for reducing the encoding time. The most time-consuming encoding steps were the DMM-1 wedgelet search and the Rate-Distortion (RD) list evaluation in Transform-Quantization and SDC flows. Consequently, we proposed a scheme composed of two solutions for speeding up the DMM-1 and one solution for reducing the RD-list size, accelerating the RD-list evaluation. The DMM-1 speeding up solutions use the information of neighbor-encoded blocks and the data contained in the border of the encoding block to accelerate the wedgelet search. The proposed scheme reduces 31.9% the encoding time with an impact of 0.272% in the Bjontegaard Delta-rate (BD-rate), surpassing the related works.