摘要
目的多视点纹理加深度视频(MVD)格式逐渐成为立体视频的主流表现形式之一。新一代高效率立体视频编码(3D-HEVC)继承了HEVC的编码结构并引入一些新的编码技术,导致深度图帧内编码过程具有较高的计算复杂度。针对这一问题,提出了一种深度图帧内编码快速算法。方法本文算法利用深度图的特征分别对CU分割过程和粗略模式选择(RMD)过程进行优化。首先在四叉树编码结构上,利用基于纹理元的图像分析方法计算编码单元的梯度矩阵,若梯度矩阵中的梯度值之和小于给定的阈值,则终止该CU的分割进程。同时,对大尺寸的PU和小尺寸的PU分别利用纹理特征与粗略模式选择过程中Planar和DC进行低复杂度率失真计算后的最小率失真代价,跳过RMD中角度模式的检查过程。结果实验结果表明,与原始算法相比,本文算法平均节省40.64%的深度图编码时间,而合成视点的平均比特率仅仅增加了0.17%。本文算法不仅能对平坦的CU跳过不必要的深度决策过程,而且有效地减少了RMD中需要遍历的模式数目,提高了编码器的效率。结论该算法对CU分割进程和粗略模式选择过程都进行优化,在合成视点的视频质量几乎不变的前提下,有效降低了深度图的帧内编码复杂度。
Objective The multi-view video plus depth （MVD） format is gradually becoming one of the main representations for 3 D videos. The 3 D high-efficiency video coding （3 D-HEVC） is the latest coding standard for compressing the MVD ibr- mat. The 3 D-HEVC inherits the coding structure of HEVC. Consequently, the splitting process of coding units （CUs） and the intra mode search process in depth map intra coding have great computational complexity. New techniques for depth map intra coding, such as depth modeling mode and simplified depth coding, have been introduced in recent years to pre- serve the sharp edges of depth maps. These techniques play an important role in the coding of depth maps. However, the adoption of these techniques further increases the computational complexity in 3D-HEVC eneoder. A fast algorithm for depth map intra coding is proposed in this study to reduce the computational complexity of depth map intra coding. Method There are a lot of large smooth regions which are separated by sharp edges in depth maps. The CU splitting process and the rough mode decision （RMD） process are improved by the proposed algorithm by using the unique characteristics of depth maps. An algorithm based on the concept of texture primitive is proposed for the hierarchical quad-tree coding structure to early terminate the CU splitting process. First, the gradient matrix of the current CU can be calculated by using the texture analysis algorithm based on texture primitive. On the basis of statistical analysis, a strong correlation between the optimal size and sum of gradient values in gradient matrix is considered for each CU. If the sum of gradient values in gradient matrix is small, then the optimal size of current CU will be large. By contrast, if the sum of gradient values in gradient matrix is large, then the optimal size of current CU will be small. Therefore, if the sum of gradient values in gradient matrix is smal- ler than a given threshold, then the CU splitting process should be terminated. For the
出处
《中国图象图形学报》
CSCD
北大核心
2018年第1期18-27,共10页
Journal of Image and Graphics
基金
福建省自然科学基金项目(2016J01306)
华侨大学研究生科研创新能力培育计划资助项目~~
