To further improve coding gain for depth map in 3D extension of High Efficiency Video Coding (3D-HEVC), many new coding techniques are introduced, which drastically increase the coding complexity. In this work, an early intra coding unit (CU) size decision scheme is proposed for 3D-HEVC intra depth map coding based on unsupervised learning approach. First, we treat the early CU size decision as a clustering problem. Then, three clustering models are developed for those CUs with the sizes of 64×64, 32×32 and 16×16 to early determine whether t...