Modification of Disparity Vector Derivation from Neighbouring Blocks in 3D-HEVC

Recently, a test model for 3D video coding extension of HEVC (3D-HEVC) has been drafted. In the model, a disparity vector (DV) derived from neighbouring blocks (NBDV) is used in the inter-view motion prediction to exploit inter-view redundancy. The accuracy of the derived DV affects prediction efficiency. In the NBDV search process, however, the first available DV among candidate DVs is chosen. It may not always be accurate. In this paper, the NBDV search process is modified. Available DVs of each direction (temporal, spatial left, spatial above) are checked based on rate distortion optimization. Optimal DVs of three directions are stored in a candidate list. When the list is not full, DVs derived from motion compensation prediction are added to the list. NBDV is finally derived by median computation of candidate DVs. The proposed method can achieve average 22.9% encoder runtimes reduction with a slight increase in bitrate.