Flexible motion model with variable size blocks for depth frames coding in colour-depth based 3D video coding

New techniques for representing 3D video are often realised using monoscopic video and associated per-pixel depth information. While the compression of both monoscopic and depth video channels can be achieved using traditional video coding techniques, in this paper, specific properties of the depth channel are exploited to further compress the depth information. More precisely, enhanced compression of the depth channel is achieved by using a highly flexible motion model, binary partition tree (BPT) which enables adaptive partitioning of the depth frames leading to better rate-distortion optimisation for inter-frame prediction. Comparing to a conventional approach, limited variable size block (LVSB) which enables only limited frame partitioning options, the presented approach brings a gain of up to 70% in bitrate reduction for the depth information.