Optimization of depth modeling modes in 3D-HEVC depth intra coding

In the development of 3D video extension of high efficiency video coding (HEVC) standard, known as 3D-HEVC, depth modeling modes (DMMs) are introduced in depth intra coding to represent object edges in depth maps. With the DMMs, a depth block is approximated by partitioning the block into two non-rectangular regions using Wedgelet or Contour partition, where each region is represented by a constant value referred to as a constant partition value (CPV). To predict the CPV more accurately and efficiently, we develop three approaches in this study. First, a better CPV predictor may be obtained by simply extending the actual depth map boundary, which can also simplify the CPV prediction by removing comparisons and average operations. Second, we propose to choose an optimal combination of delta CPVs in terms of view synthesis optimization at the encoder by checking more candidates. Finally, zero residual coding is suggested for DMMs coding units in the rate-distortion optimization loop. Experimental results demonstrate that about 0.2 and 0.1 % Bjøntegaard delta rate saving can be achieved on average for synthesized views with less complexity, under the all-intra and random access configurations, respectively.