Backward view synthesis prediction for 3D-HEVC

View synthesis prediction provides an effective way to reduce inter-view redundancy of multiview video in addition to conventional disparity compensated prediction. Traditional forward warping techniques incur high complexity since an entire picture is typically warped from one viewpoint to another. To reduce this complexity, block-based backward warping is considered as an alternative solution. One difficulty with this approach is that it requires depth information of the current block prior to its encoding. To solve this problem, a novel method is proposed to derive the depth information from neighboring blocks with high accuracy. With the proposed approach, backward warping is enabled using depth information derived from either neighboring spatial (inter-view) compensated blocks or temporal compensated blocks. As a generalization, the proposed backward warping scheme is not only applied at the pixel level, but at the sub-block level as well. Simulation results demonstrate that the proposed scheme achieves an average bitrate savings of 1.2% for coded video vs coded video bitrate, 1.1% for coded video vs total bitrate, and 1.0% for synthesized video vs total bitrate under common test conditions for 3D video coding using HEVC, with maximum gains of greater than 10% for dependent views.