Differentiation of Signature Traits vis‐à‐vis Mobile‐ and Table‐Based Digitizers

As the use of signatures for identification purposes is pervasive in society and has a long history in business, dynamic signature verification (DSV) could be an answer to authenticating a document signed electronically and establishing the identity of that document in a dispute. DSV has the advantage in that traits of the signature can be collected on a digitizer. The research question of this paper is to understand how the individual variables vary across devices. In applied applications, this is important because if the signature variables change across the digitizers this will impact performance and the ability to use those variable. Understanding which traits are consistent across devices will aid dynamic signature algorithm designers to create more robust algorithms.     

Concentric Circle‐Based Image Signature for Near‐Duplicate Detection in Large Databases

Many applications dealing with image management need a technique for removing duplicate images or for grouping related (near‐duplicate) images in a database. This paper proposes a concentric circle‐based image signature which makes it possible to detect near‐duplicates rapidly and accurately. An image is partitioned by radius and angle levels from the center of the image. Feature values are calculated using the average or variation between the partitioned sub‐regions. The feature values distributed in sequence are formed into an image signature by hash generation. The hashing facilitates storage space reduction and fast matching. The performance was evaluated through discriminability and robustness tests. Using these tests, the particularity among the different images and the invariability among the modified images are verified, respectively. In addition, we also measured the discriminability and robustness by the distribution analysis of the hashed bits. The proposed method is robust to various modifications, as shown by its average detection rate of 98.99%. The experimental results showed that the proposed method is suitable for near‐duplicate detection in large databases.     

MPEG-2视频码流系统头错误分析与控制算法

MPEG－2标准是视频通信的一个重要标准，此标准中的视频头是码流最重要的数据，因此在详细地分析基于MPEG－2标准视频头错误的基础上，提出了视频头错误数据结构的控制算法，并通过实验证明该算法有很好的视频头纠错效果。     

基于视频的车辆检测中检测与去除阴影的一种有效方法

本文针对视频车辆检测系统中的关键步骤-视频检测中的阴影去除进行深入研究,在分析了阴影产生的原因和阴影的特点之后,综合利用灰度图像及其差分后的二值化图像,提出了一种基于背景差分的检测与去除阴影的新方法.实验证明,该方法能够较好地去除运动车辆的阴影,保留比较完整的车辆目标信息, 为准确提取车辆目标奠定了基础.     

基于视觉特性的视频压缩预处理方法的研究

视频压缩的最根本目的是以尽量少的比特数来表征视频流,同时保证视频的主观质量,使其符合应用场合的要求.对于视频信号,人眼是最终的信号接收者,因此视频的编码压缩应当考虑人眼的主观视觉效果.基于此观点,本文讨论了利用人眼的视觉特性,对视频进行处理优化后再进行正常的编码压缩传输.实验结果表明,本文采用的预处理算法在提高压缩比的同时可以有效地保证视频质量;在对原始视频进行相同程度压缩时,本文算法预处理后获得的视频主观质量明显好于原始直接压缩.     

一种基于最佳比特分配策略的三维小波视频编码新方法

对基于三维小波变换的视频编码进行了研究。由于视频图像传统的三维小波变换结构存在着诸多不足．文章提出了一种改进的三维小波变换结构。在给定的比特率条件下，通过对使得解码图像量化误差达到最小的最佳比特分配策略进行研究，给出了在均匀量化情况下的改进三维小波变换结构的量化步长。实验结果表明该方法的压缩性能明显优于传统方法。     

一种快速参数估计的多视点图像颜色校正方法

提出了一种基于快速确定参数的全局直方图匹配的颜色校正方法,对于标准的多视点视频序列,利用直方图,分别快速估算出其在RGB,YUV,CIELab这3个颜色空间下的3个分量线性方程的参数值,在MATLAB环境下仿真出3个不同颜色空间中的校正结果,并对其进行分析和比较,实验结果表明了该方法的有效性和可靠性。     

An SSD‐Based Storage System for an Interactive Media Server Using Video Frame Grouping

For real‐time interactive multimedia operations, such as video uploading, video play, fast‐forward, and fast‐rewind, solid state disk (SSD)‐based storage systems for video streaming servers are becoming more important. Random access rates in storage systems increase significantly with the number of users; it is thus difficult to simultaneously serve many users with HDD‐based storage systems, which have low random access performance. Because there is no mechanical operation in NAND flash‐based SSDs, they outperform HDDs in terms of flexible random access operation. In addition, due to the multichannel architecture of SSDs, they perform similarly to HDDs in terms of sequential access. In this paper, we propose a new SSD‐based storage system for interactive media servers. Based on the proposed method, it is possible to maximize the channel utilization of the SSD's multichannel architecture. Accordingly, we can improve the performance of SSD‐based storage systems for interactive media operations.     

A Time‐Optimal Anti‐collision Algorithm for FSA‐Based RFID Systems

With the introduction of the new generation RFID technology, EPCglobal Class‐1 Generation‐2, there is considerable interest in improving the performance of the framed slotted Aloha (FSA)‐based tag collision arbitration protocol. We suggest a novel time‐optimal anti‐collision algorithm for the FSA protocol. Our performance evaluation demonstrates that our algorithm outperforms other tag collision arbitration schemes.     

一种基于变异灰度直方图的视频字幕检测定位方法

为实现视频图像中字幕的快速检测与定位,本文提出一种变异灰度直方图VGH.文章给出VGH的定义,对其中的特征及其与图像中字幕的映射关系作了分析,并在此基础上给出视频字幕的检测与定位方法.该方法将垂直子图像转换为基于行的VGH (VGH^R),将水平子图像转换为基于列的VGH (VGH^C),通过对其中的凹谷特征和梳状凸台特征的识别,实现对字幕的检测与定位.文章最后给出某些实验结果,表明了算法的有效性.     

一种基于模糊理论的雷达与视频融合交通目标跟踪方法

为了解决单传感器在道路监测中存在的局限性以及交通环境多样化等问题,基于模糊集理论的一种目标决策标准对传统的数据融合算法进行改进。该方法利用决策层模糊集理论的多传感器融合算法对交通目标进行跟踪,采用Z型隶属函数用于决策分支的优化。与传统的算法相比,改进后的数据融合算法对雷达航迹冗余、视频干扰和目标分割等问题都有所改善,并且进一步提高了跟踪精度。收集了大量的实际交通数据来验证雷达和视频跟踪算法的有效性,实验结果表明多传感器融合算法优于单传感器的目标跟踪算法。     

降低头肩视频序列编码码率的一种新方法

在头肩视频低码率编码的情况下,需要准确判定不编码宏块,从而节省码字。本文描述了一个基于运动矢量扫描的新算法,能够预测运动区域和静态背景区域,并在保证感兴趣区域质量的情况下,对静态区域的大部分宏块不编码。实验结果显示在低码率下,该算法能够大大节约编码的码字,而且在小运动序列时,可以显著减少编码的时间。     

基于关键帧颜色和纹理特征的视频拷贝检测

提出了一种基于关键帧颜色和纹理特征的视频拷贝检测方法。首先通过子片段方法提取视频的关键帧,然后将关键帧分成3个子块,提取每个子块的三维量化颜色直方图,通过直方图相交法来进行颜色特征的匹配。对检索得到的结果视频关键帧进行纹理特征提取,通过其灰度共生矩阵的角二阶矩和熵来表征其纹理特征,纹理特征的匹配可进一步过滤不相关的视频。实验结果表明,该方法效果好、稳健性强且可应用于多种类型的视频。     

Framework for Content‐Based Image Identification with Standardized Multiview Features

Information identification with image data by means of low‐level visual features has evolved as a challenging research domain. Conventional text‐based mapping of image data has been gradually replaced by content‐based techniques of image identification. Feature extraction from image content plays a crucial role in facilitating content‐based detection processes. In this paper, the authors have proposed four different techniques for multiview feature extraction from images. The efficiency of extracted feature vectors for content‐based image classification and retrieval is evaluated by means of fusion‐based and data standardization–based techniques. It is observed that the latter surpasses the former. The proposed methods outclass state‐of‐the‐art techniques for content‐based image identification and show an average increase in precision of 17.71% and 22.78% for classification and retrieval, respectively. Three public datasets — Wang; Oliva and Torralba (OT‐Scene); and Corel — are used for verification purposes. The research findings are statistically validated by conducting a paired t‐test.     

基于小波空间的图像分解变分模型

本文从不同的角度考虑OSV模型,提出一种基于全变差和H^-1范数的图像分解变分模型.通过分析OSV模型的性质,给出该模型基于小波空间的非线性偏微分方程和迭代算法.同时,从理论上分析了该模型的极小值存在性.实验表明该方法具有可行性.     

一种新的信号识别和扩频码捕获(SR/CA)算法

DS-SS系统中信号识别和扩频码捕获(SR/CA)会存在检测概率和虚警概率难以同时优化的矛盾,在分析现有SR/CA算法的基础上,提出了一种带有频偏估计的软SR/CA算法。通过引入高低双重判决门限和频偏估计校正环路,该算法在保持较低的虚警概率的条件下能提高信号的检测概率。数值仿真结果表明,软SR/CA算法结构相对传统的SR/CA算法能在检测概率和虚警概率之间取得较好的折衷。     

基于轨道匹配和改进的空间目标识别方法

空间目标识别就是对外层空间运行的目标进行类型或属性辨认。空间目标一般是沿着固有轨道运动的目标,它的轨道根数是表征其运行规律的主要参数,也是进行空间识别的基础。该文提出了一种基于轨道匹配改进的空间目标识别方法。利用空间目标运动的规律性,对目标的雷达观测数据进行初轨计算、轨道匹配和轨道改进三个部分的处理,对目标的不同圈次观测数据进行关联和积累,并在优化轨道根数的同时实现对空间目标的匹配识别。针对匹配识别模糊情况,通过分析比较轨道改进收敛时的根数内符合误差和观测数据的残差,确定最可能的匹配识别结果。仿真实验结果说明了该方法的有效性。     

An SAD‐Based Selective Bi‐prediction Method for Fast Motion Estimation in High Efficiency Video Coding

As the next‐generation video coding standard, High Efficiency Video Coding (HEVC) has adopted advanced coding tools despite the increase in computational complexity. In this paper, we propose a selective bi‐prediction method to reduce the encoding complexity of HEVC. The proposed method evaluates the statistical property of the sum of absolute differences in the motion estimation process and determines whether bi‐prediction is performed. A performance comparison of the complexity reduction is provided to show the effectiveness of the proposed method compared to the HEVC test model version 4.0. On average, 50% of the bi‐prediction time can be reduced by the proposed method, while maintaining a negligible bit increment and a minimal loss of image quality.     

A pilot‐aided detector for spectrum sensing of Digital Video Broadcasting—Terrestrial signals in cognitive radio networks

In this paper, the main properties of digital television broadcasting signals based on the Digital Video Broadcasting—Terrestrial (DVB‐T) standard are analyzed, and these properties are utilized to design a new pilot‐aided detector for spectrum sensing in cognitive radio networks. The proposed detector consists of a processing unit and a combination and decision unit. In the processing unit, multiple statistics that correspond to different enhanced pilot components are computed. In the combination and decision unit, three newly proposed combination schemes are adopted to combine these statistics, and then, a final decision on the presence or absence of the DVB‐T signals is made on the basis of the Neyman–Pearson criterion. The proposed pilot‐aided detector exploits both the periodic continual and scattered pilots that are intrinsic in the DVB‐T signals, processes the observed data timely, experiences short sensing duration, and requires no time synchronization information. Furthermore, the proposed pilot‐aided detector is able to distinguish DVB‐T signals from interference. Theoretical analysis and simulation results show that spectrum bands that are not currently occupied by the DVB‐T systems can be detected accurately by using the proposed pilot‐aided detector. Simulation results also demonstrate the significant performance gain of the proposed detector compared with the counterparts.Copyright © 2011 John Wiley & Sons, Ltd.     

High‐Performance Spatial and Temporal Error‐Concealment Algorithms for Block‐Based Video Coding Techniques

A compressed video bitstream is sensitive to errors that may severely degrade the reconstructed images even when the bit error rate is small. One approach to combat the impact of such errors is the use of error concealment at the decoder without increasing the bit rate or changing the encoder. For spatial‐error concealment, we propose a method featuring edge continuity and texture preservation as well as low computation to reconstruct more visually acceptable images. Aiming at temporal error concealment, we propose a two‐step algorithm based on block matching principles in which the assumption of smooth and uniform motion for some adjacent blocks is adopted. As simulation results show, the proposed spatial and temporal methods provide better reconstruction quality for damaged images than other methods.