A Fast Depth-Map Wedgelet Partitioning Scheme for
Intra Prediction in 3D Video Coding
Mengmeng Zhang, Chuan Zhao
North China University of Technology
Beijing, P.R.China
zmm@ncut.edu.cn,
dynamiter@sohu.com
Jizheng Xu
Microsoft Research Asia
Beijing, P.R.China
jzxu@mircosoft.com
Huihui Bai
Beijing Jiaotong University
Beijing, P.R.China
luckybhh@gmail.com
Abstract—By employing 35 intra prediction modes, HEVC
standard performs better to remove spatial redundancy between
the current block and its neighbors. Although 3D video coding
has adopted HEVC intra prediction and Depth Modeling Modes
(DMM) technology to improve the performance, the Explicit
Wedgelet Partition Mode within DMM brings unaffordable
complexity to compress depth map. Based on the way of
obtaining the picture texture from the mode with Sum of
Absolute Transform Difference in rough mode decision, we
propose a fast scheme to determine Wedgelet Partition in intra
prediction, which leads to significant computational saving with
marginal BD-rate increase after decoder-side view synthesis.
I. INTRODUCTION
The HEVC [1] standard is close to be finalized and will be
approved as International Standard in January 2013. Several
extensions on top of HEVC are discussed within JCT-VC
(Joint Collaborative Team on Video Coding), such as 3D
video coding [2]. 3DV-HTM3.0 [3] is the latest the test model
released with HEVC technology, where many improved
Multiview Video Coding algorithms are contained. The well-
known concept of disparity-compensated prediction (DCP)
has been added as an alternative to motion-compensated
prediction. Then, the QP adjustment method is developed in
order to improve perceptual quality of coded texture. What’s
more, a straightforward approach to the synthesized view
distortion change [4] is used as distortion measure to
overcome the computational complexity.
In the extension, 3D video is represented by the Multiview
Video plus depth [5] with 2-3 views, which includes texture
views as well as associated depth maps. The decoding video
and depth image synthesize additional intermediate views
suitable for displaying the 3D content on an auto-stereoscopic
by using the advanced Depth-Image-Based rendering
techniques. Although the depth maps are not viewed by end
users, they directly affect the image generation in decoding.
Therefore, it is important to compress depth maps in a way
that it minimizes distortion in views rendered with them.
For compressing depth maps in HTM-3.0, basically the
same concepts of intra-prediction, motion-compensated
prediction, disparity-compensated prediction, and transform
coding as for the coding of the video pictures are used.
However, some tools have been modified for depth map
coding. Chrominance coding is disabled in the sampling
format, and in-loop filters including de-blocking filter,
adaptive loop filter, and sample-adaptive loop filter are less
useful in coding depth map for saving the encoding and
decoding complexity. A new Znear-Zfar compensated
weighted prediction is designed especially for inter-frame
depth coding to overcome the problem of depth map reference
frame choice. Unlike HEVC intra prediction coding, Depth
Modeling Modes (DMM) [6] are designed to the intra
prediction for the sharp edges mainly charactering the depth
map. For avoiding the ring artifacts at sharp edges in depth
maps and for decreasing the encoder and decoder complexity,
the motion-compensated prediction as well as the disparity-
compensated prediction has been modified in a way that no
interpolation is used. That means, for depth maps, the
inter-picture prediction is always performed with full-sample
accuracy. Considering that the video signal and its associated
depth is graphically similar from the same viewpoint, the
Motion Parameter Inheritance [8] mode is extended to deal
with inheriting the motion data and the partitioning of the inter
prediction.
However, searching DMM parameters in depth map intra
prediction introduces unacceptable consuming time, which is
about 30 times as much as encoding the corresponding texture
image by HEVC based on the experiment result. This paper
analyzes DMM irrational operations and proposes to simplify
the searching in Wedgelet Partition of DMM. We make full
use of the mode with minimal Sum of Absolute Transform
Difference(SATD) cost and find correlations between the
mode and Wedgelet Partition to simplify the our experiments.
The rest of this paper is organized as follows. SectionII
reviews the Depth Modeling Mode technique in 3D video
coding. Section III introduces our proposed method by using
the SATD mode for reducing the full Wedgelet Partition
process. Experimental results and conclusions are given in
Section VI and Section V, respectively.
This work is supported by the Natural National Science
Foundation of China under No. 61103113 and
o.61272051,Jiangsu Provincial Natural Science
Foundation BK2011455, KM201310009004 .
978-1-4673-5762-3/13/$31.00 ©2013 IEEE 2852