Low-Complexity Scalable Extension of the High-Efficiency Video Coding (SHVC) Encoding System

Abstract

The scalable extension of the high-efficiency video coding (SHVC) system adopts a hierarchical quadtree-based coding unit (CU) that is suitable for various texture and motion properties of videos. Currently, the test model of SHVC identifies the optimal CU size by performing an exhaustive quadtree depth-level search, which achieves a high compression efficiency at a heavy cost in terms of the computational complexity. However, many interactive multimedia applications, such as remote monitoring and video surveillance, which are sensitive to time delays, have insufficient computational power for coding high-definition (HD) and ultra-high-definition (UHD) videos. Therefore, it is important, yet challenging, to optimize the SHVC coding procedure and accelerate video coding. In this article, we propose a fast CU quadtree depth-level decision algorithm for inter-frames on enhancement layers that is based on an analysis of inter-layer, spatial, and temporal correlations. When motion/texture properties of coding regions can be identified early, a fast algorithm can be designed for adapting CU depth-level decision procedures to video contents and avoiding unnecessary computations during CU depth-level traversal. The proposed algorithm determines the motion activity level at the treeblock size of the hierarchical quadtree by utilizing motion vectors from its corresponding blocks at the base layer. Based on the motion activity level, neighboring encoded CUs that have larger correlations are preferentially selected to predict the optimal depth level of the current treeblock. Finally, two parameters, namely, the motion activity level and the predicted CU depth level, are used to identify a subset of candidate CU depth levels and adaptively optimize CU depth-level decision processes. The experimental results demonstrate that the proposed scheme can run approximately three times faster than the most recent SHVC reference software, with a negligible loss of compression efficiency. The proposed scheme is efficient for all types of scalable video sequences under various coding conditions and outperforms state-of-the-art fast SHVC and HEVC algorithms. Our scheme is a suitable candidate for interactive HD/UHD video applications that are expected to operate in real-time and power-constrained scenarios.