17360670
Priority search technique for MPEG-4 motion estimation of arbitrarily shaped video object
One of the main differences between MPEG-4 and previously standardized video coding schemes is the support of arbitrarily shaped video objects, for which most of the existing fast motion estimation algorithms are not suitable. The conventional fast motion estimation algorithm works well for opaque macroblocks, but not in the case of a boundary macroblock which contains a large number of local minima on its error surface. We propose a fast search algorithm which incorporates the binary alpha-plane to predict accurately the motion vectors of boundary macroblocks. Besides, these accurate motion vectors can be used to develop a novel priority search algorithm which is an efficient search strategy for the remaining opaque macroblocks. Experimental results show that, compared to the conventional methods, our approach requires a low computational complexity and provides a significant improvement in terms of accuracy in motion-compensated video object planes.
6180081
New adaptive partial distortion search using clustered pixel matching error characteristic
The partial distortion search is a particularly attractive fast block-matching algorithm, because it introduces no prediction error as compared with the full-search algorithm. It reduces the number of necessary matching evaluations for every searching point to save computation. In the literature, many researches have tried to improve block-matching algorithms by making use of an assumption that pixels with larger gradient magnitudes have larger matching errors on average. Based on a simple analysis, we have found that on average, pixel matching errors with similar magnitudes tend to appear in clusters for natural video sequences. By using this clustering characteristic, we propose an adaptive partial distortion search algorithm which significantly improves the computational efficiency of the original PDS. This approach is much better than other pixel gradient based adaptive PDS algorithms. In addition, our proposed algorithm is suitable for motion estimation of both opaque and boundary macroblocks of an arbitrary shaped object in MPEG-4 coding.
1507754
A compressed-domain heterogeneous video transcoder
The forthcoming multimedia telecommunication services are expected to use pre-encoded videos for storage and transmission. The heterogeneities of the present communication networks and the clients' devices demand matching the encoding format of the video source to the constraints of the networks and clients' devices. In order to provide quality support services to heterogeneous clients or transmission channels, the video server should have the capability of performing heterogeneous transcoding, which is regarded as a process of converting a previously compressed video bitstream into another bitstream with a different format. However, much investigation has been conducted to focus on homogeneous transcoding. Only a limited number of methods have been proposed to realize the heterogeneous transcoding from MPEG-2 to H.263. The major difficulties for transcoding B-picture to P-picture is that the incoming DCT coefficients arc predicted from the forward and backward prediction. In other words, the DCT coefficients predicted from the previous frame is not available. Therefore, the required new prediction errors need to be reestimated in the pixel domain. This process involves high computational complexity as well as introduces reencoding errors. Motivated by this, we propose a new transcoder architecture to convert a B-picture into a P-picture by making use of the techniques of motion compensation in the DCT domain and indirect addition of DCT coefficients. In this paper, we derive a set of equations and formulate the problem of how to obtain the DCT coefficients. Experimental results show that the proposed video transcoder achieve a better performance as compared to the conventional video transcoder in terms of both quality and complexity. Furthermore, we propose a fast algorithm to speed up the transcoding process making use of the correlation of motion activities between pictures.
7668661
Evaluation on security and privacy of Web-based learning systems
Web-based learning systems are becoming popular in the recent years. Many courses and lectures are now conducted online. Similar to other Web-based applications, security and privacy of Web-based learning systems should not be overlooked. We evaluate the security and privacy of general Web-based learning systems. We address the security and privacy requirements specific to them. Recommendations on design and implementation of a secure Web-based learning system are also presented. In particular, we have evaluated the security services of two popular Web-based learning tools.
11665411
Investigating Information Systems Strategic Alignment
Although strategic alignment is an important theoretical concept, and achieving alignment or fit among organizational elements would seem to be an important business objective, empirical demonstrations of the importance of alignment have been uncommon (White 1986). This study attempted to provide an empirical assessment of the nature and importance of information systems strategic alignlnent There is much discussion today about the importance of 1. THE CONCEPTUAL MODEL strategic alignment in general (e.g., Venkatraman and Camillus 1984; White 1986) and information systems (IS) The conceptual model underlying the study is depicted in strategic alignment in particular (e.g., Elam et al. 1988; Figure 1. It depicts the propositions that IS.strategic Henderson and Thomas 1992; Henderson and Venkatraman 1992; Keen 1991; Ward, Griffiths and Whitmore 1990). alignment, defined as the fit existing between business The discussion generally suggests that the better the alignstrategy and IS strategy, impacts performance at the IS ment, the better the expected company performance. level and at the overall business level. However, there have been few empirical verifications of this proposition (White 1986). In addition, the discussion The results of the overall study, and detailed descriptions of about alignment has tended to be imprecise and vague (Van the instruments used to measure business strategy, IS de Ven and Drazin 1985). Important objectives of this strategy, IS effectiveness and business performance, have study were to identify a useful, precise model for the IS been described in Chan et al. (1993) and Chan and Huff strategic alignment construct and to examine empirically (1992) respectively. (Table 1 provides a brief outline of relationships among IS strategic alignment; IS effectiveness, the overall study.) This paper discusses the derivation and and business performance. significance of the IS strategic alignment computations and The discussion opens with a brief overview of the concepthe study's findings regarding alignment tual model underlying this study. Next, instruments that measure business strategy and IS strategy are introduced. Then instruments that measure IS effectiveness and business performance are outlined. This is followed by a 2. MEASURING BUSINESS STRATEGY AND general discussion of various approaches that are used to INFORMATION SYSTEMS STRATEGY assess alignment. Specific models of alignment are evaluated and the primary model for IS strategic alignment used within this research is selected and described. The links In order to assess IS strategic alignment, there needed to be between IS strategic alignment and performance are then assessments of both business strategy and IS strategy. discussed. Finally, the paper concludes with a description Table 2 lists the dimensions of these constructs as operaof the study's implications for management and future tionalized in this study. Multiple indicators were used to research. measure each dimension.
894881
Performance improvement of TCP Vegas over heterogeneous networks
Current IP network has become the dominant paradigm for all networking environments. The significant cause of packet losses in such heterogenous networks is no longer limited to network congestion. Traditional TCP interprets every packet loss as caused by congestion which may be not the case in the current Internet. Misinterpretation of wireless random loss as an indication of network congestion results in TCP slowing down its sending rate unnecessarily. We propose a new variant of TCP Vegas named RedVegas. By using the innate nature of Vegas and congestion indications marked by routers, RedVegas may detect random packet losses precisely. Through the packet loss differentiation, RedVegas reacts appropriately to the losses, and therefore the throughput of connection over heterogeneous networks can be significantly improved.
10812167
A TCP-Friendly Stateless AQM Scheme for Fair Bandwidth Allocation
Queue management, bandwidth share, and congestion control are very important to both robustness and fairness of the Internet. In this article, we investigate the problem of providing a fair bandwidth allocation to those flows that share congested link in a router. A new TCP-friendly router-based AQM (active queue management) scheme, termed WARD, is proposed to approximate the fair queueing policy. WARD is a simple packet dropping algorithm with a random mechanism, and discriminates against the flows which transmit more packets than allowed. By doing this, it not only protects TCP connections from UDP flows, but also solves the problem of competing bandwidth among different TCP versions such as TCP Vegas and Reno. In addition, WARD works quite well for TCP flow isolation even with different round trip times. In other words, WARD improves the unfair bandwidth allocation properties. Furthermore, it is stateless and easy to implement, so WARD controls unresponsive or misbehaving flows with a minimum overhead
28992997
Creating reusable WebQuest objects with WebQuest authoring engine
WebQuest is a constructivist lesson format for Web-enabled inquiry-based learning. A WebQuest exists in form of a Web site that contains a collection of Web pages. In this paper, we define the "WebQuest Object" which is basically a learning object. We also present the WebQuest authoring engine which enables one to generate WebQuest objects without the knowledge in Web page construction and publishing. The WebQuest authoring engine also allows ones to edit the metadata of the WebQuest so as to facilitate the reuse of the WebQuest objects.