Shengfu Dong

Local Stereo Matching with Improved Matching Cost and Disparity Refinement

Recent local stereo matching methods have achieved comparable performance with global methods. However, the final disparity map still contains significant outliers. In this article, the authors propose a local stereo matching method that employs a new combined cost approach and a secondary disparity refinement mechanism. They formulate combined cost using a modified color census transform and truncated absolute differences of color and gradients. They also use symmetric guided filter for cost aggregation. Unlike in traditional stereo matching, they propose a novel secondary disparity refinement to further remove the remaining outliers. Experimental results on the Middlebury benchmark show that their method ranks fifth out of 153 submitted methods, and its the best cost-volume filtering-based local method. Experiments on real-world sequences and depth-based applications also validate the proposed methods effectiveness.

Fast intra mode decision algorithm based on refinement in HEVC

High Efficiency Video Coding (HEVC) is the next generation video compression standard providing significant coding performance. It adopts 35 intra prediction modes with larger CU size to improve the intra encoding efficiency, so that cause a high computational complexity. In this paper, two fast intra-prediction algorithms are proposed to reduce the number of candidate modes for rate-distortion (RD) optimization. We obtain an optimal adjacent modes (OAM) list consisting of dominant directions through the analysis of costs of several general direction modes. Furthermore, we improve the most probable mode (MPM) algorithm to make full use of the spatial correlation between neighbour prediction blocks instead of simply merging the prediction modes of neighbour prediction blocks into the candidate list. Experimental results show that the proposed algorithms can reduce about 27.3% of the encoding time compared to the HEVC test model 14.0, while the decrease of coding quality is negligible.

A system for automatic Chinese seal imprint verification

Chinese seal imprint verification by computer is very difficult, but is much needed by the application. An improved method for seal imprint verification based on stroke edge matching combined with image difference analysis is proposed. Experimental results show that the proposed approach is excellent in consistency, reliability and adaptability and is feasible for practical applications.

Fast motion estimation methods for HEVC

Compared with H.264, the High Efficiency Video Coding standard has higher compression efficiency and better transmission performance, and will be used in wider field. TZ search method is adopted to perform integer pixel search in HEVC. Its performance is very perfect but very time-consuming. In this paper, we use hexagon search method in place of TZ search method to speed up motion estimation process. Simulation results show that this scheme accelerates 2-6 times and the performance loss is negligible in sequences with slow movements.

HEVC decoder acceleration on multi-core X86 platform

In this paper, we propose a hybrid parallel decoding strategy for HEVC which combines task-level parallelism and datalevel parallelism based on CTUs. The data-level parallelism makes the execution time distribution of different decoding stages more balanced, and makes the task-level parallelism more efficient. Our approach imposes no constraint on bit streams that they shall be generated by optional parallel coding tools such as tiles or WPP, so it can be applied for all kinds of HEVC bit streams. Furthermore, SSE, a typical SIMD instruction set on X86 platform, is utilized to accelerate time-consuming modules, which shortens the execution time gaps between different stages and make them in favor of parallel processing. We have implemented these acceleration strategies on HM-10.0 decoder, and a great speed-up ratio is achieved.

A novel integer-pixel motion estimation algorithm based on quadratic prediction

This paper presents a fast integer-pixel motion estimation (ME) algorithm for High Efficiency Video Coding (HEVC), which provides a strategy to speed up the search process significantly, while yielding the same quality performance as the Test Zone Search (TZSearch) scheme in HEVC Test Model (HM). Compared with the H.264/AVC, the ME process employs a more complex hybrid coding architecture and a larger size search window in HEVC, leading to great computational complexity. We utilize limited pixels of certain position in the current search range to build a quadratic model, and then shrink the search range repeatedly by analyzing the sum of absolute difference (SAD) distribution until the best motion vector (MV) is obtained. The proposed algorithm can be applied to various encoding conditions. Experimental results show that our method can save 56% of computations compared with the TZSearch scheme, with negligible decrease of coding quality.

Depth Template Based 2D-to-3D Video Conversion and Coding System

A Depth Template based 2D-to-3D Video Conversion and Coding system (DTVCC) is proposed by this paper. In DTVCC, triangle meshes are exploited to describe depth template for scenes in 2D video, an interactive system is designed to generate reliable depth template, depth map can be automatically reconstructed based on the depth template and 2D video frame pixels information, and the generated 3D video is compressed just by coding the 2D video plus depth template. Experiment results show that not only high quality 3D video is generated, but also the bit rate of coding the converted 3D video is saved by 12%~38% with our proposed system of DTVCC.

An all-zero blocks early detection method for high-efficiency video coding

The High Efficiency Video Coding has a significant compression performance benefit versus previous standards. Thanks to the high efficiency prediction tools, blocks with all-zero quantized transform coefficients are quite common in HEVC. The computation load of transform and quantization can be remarkably reduced if the all-zero blocks can be detected prior to transform and quantization. Based on the theoretical analysis of the integer transform and quantization process in HEVC, we propose some SAD thresholds under which all-zero block can be detected. Simulation results show that with our proposed method, nearly 37% time saving for computation time of transform and quantization can be saved.

Acceleration of HEVC transform and inverse transform on ARM NEON platform

HEVC (High Efficiency Video Coding) has recently been published as the next generation video coding standard. Compared with previous standards, the coding efficiency is greatly improved at the cost of much higher codec complexity. On the other hand, ARM with SIMD (Single Instruction Multiple Data) instructions is widely deployed on mobile platform, which makes it feasible to accelerate multimedia applications by software. However, the accelerations are not straight forward, and the modules have to be carefully redesigned to utilize SIMD instructions efficiently. Transform and inverse transform modules are frequently called in HEVC codec. In this paper, we propose an acceleration method of the transform and inverse transform by utilizing the data level parallelism on NEON platform. Experiment results show that the speed of these modules has been increased considerably.

High definition IEEE AVS decoder on ARM NEON platform

Nowadays, mobile devices are capable of displaying video up to HD resolution. In this paper, we propose two acceleration strategies for Audio Video coding Standard (AVS) software decoder on multi-core ARM NEON platform. Firstly, data level parallelism is utilized to effectively use the SIMD capability of NEON and key modules are redesigned to make them SIMD friendly. Secondly, a macroblock level wavefront parallelism is designed based on the decoding dependencies among macroblocks to utilize the processing capability of multiple cores. Experiment results show that AVS (IEEE 1857) HD video stream can be decoded in real-time by applying the proposed two acceleration strategies.