8253940
A pinhole camera modeling of motion vector field for tennis video analysis
The motion vector field (MVF) represents motion characteristics in video sequences, and has been widely used and been proved to be effective in sports video analysis. However, in tennis video analysis, MVF-based methods are seldom utilized for the reasons that: (i) the players' true motion is not accurately represented by the extracted motion vector, due to the deformation caused by the diagonal shooting of the camera; and (ii) the motion vector's magnitude is not prominent enough and is prone to be disturbed by noises. In this paper, a pinhole camera modeling of the motion vector field is proposed to revise the deformed motion vector. In this modeling, a foreground object mask is adopted and global motion compensation is incorporated as the pre-processing steps. Evaluation of the proposed modeling using four hours of tennis videos shows very encouraging results.
5295208
Bit rate reduction of H.264/AVC video coding for mobile applications
The increasing use of mobile applications requires higher compression efficiency for video coding. However, in mobile applications, the capability of the processor is limited and the channel is unreliable. Since the emerging H.264/AVC video coding standard provides superior compression performance compared to all the existing video coding standards, many research efforts concentrate on the compression efficiency of intra-frame coding in H.264/AVC. In this paper, we propose a novel algorithm to reduce the bit rate compressed by H.264/AVC intra-frame coding. We focus on the method to code the intra-frame prediction modes. Our proposed method significantly reduces the bits used to code the modes and do not change the syntax of the bit stream. Experimental results demonstrate it is effective and efficient
709845
Supporting Live Video on Ad Hoc Wireless Networks: Unbalanced Multiple Description Coding, Single Path Transport and Recursive Error Concealment
Robust transmission of live video over ad hoc wireless networks presents new challenges: high bandwidth requirements are coupled with delay constraints; nodes are constrained in processing power and storage capacity; ad hoc wireless networks suffer from bursty packet losses that drastically degrade the viewing experience. Accordingly, we propose a simple, but practical unbalanced multiple description (UMD) codec that uses single path transport only. At the UMD decoder, the lost Low- Resolution (LR) frames can be receded from the corresponding ones of the correctly received High- Resolution (HR) stream. This makes LR more robust to packet losses and ensures continuous video playback. The simulation results show that the proposed UMD codec has higher decoded quality, smaller quality fluctuation and lower probability of pause than other error resilience techniques, especially when channel burstiness becomes large. We also propose a novel sequence-based error concealment (EC) algorithm for our UMD decoder. It recursively uses multi-frame recovery principle to frame-by-frame reduce error drift in the HR description with respect to the LR description. In fact, the algorithm can be applied to most UMD schemes. It has the advantage of working on integer-, half- or quarter- pixel precision and looking backward without buffering future frames. Experimental results show that error decreases the fastest if the UMD decoder uses our EC algorithm. It can provide satisfactory performance on both objective and subjective evaluation.
5815107
SIKAS: A Scalable Distributed Key Management Scheme for Dynamic Collaborative Groups
The increasing popularity of distributed and collaborative applications prompts the need for secure communication in collaborative groups. Some distributed collaborative key management protocols have been proposed to provide group communication privacy and data confidentiality for collaborative groups. However, most of them rekey on each member change, and the costs of group rekeying can be quite substantial for large groups with frequent membership changes. In this paper, we propose a scalable distributed key management scheme using a distributed one-way function tree named SIKAS which can significantly reduce the computation and communication costs of maintaining the group key based upon period-based group rekeying. A comparison with previous work has shown that SIKAS provides scalability and rekeying efficiency while preserving both distributed and collaborative properties
28617398
An Unbalanced Multiple Description Coding Scheme for Video Transmission Over Wireless Ad Hoc Networks
16772027
CCL-SVC: Optimizing user experience of broadcasting video on computation capability limited handheld devices
In this paper, we propose a novel scheme using computing complexity layered scalable video coding (CCLSVC) to optimize the user experience of broadcasting video in the computing capability limited handheld terminals. To address the heterogeneity of computing capability among different handheld devices, we employ hierarchal B reference structure of SVC to divide the frames into multiple computing complexity layers (CC Layers) in server side. The handheld clients simply choose to decode the frames in their corresponding layers in terms of their computation capability to maximize the video PSNR. We have proved that the optimal CC Layers division problem is a precedence constrained scheduling problem, which is an NP-complete problem. And we further propose our fast greedy method to approximately get optimized broadcasting video playback PSNR. The simulation shows that our method is superior to temporal SVC and random frame discarding method.
62585345
An effective collision resolution mechanism for wireless LAN
Based on the current standardized IEEE 802.11 distributed coordination function (DCF) protocol, this paper proposes a new efficient collision resolution mechanism, called GDCF (gentle DCF). Our main motivation is based on the observation that 802.11 DCF decreases the contention window to the initial value after each success transmission, which essentially assumes that each successful transmission is an indication that the system is under low traffic loading. GDCF takes a more conservative measure by halving the contention window size after c consecutive successful transmissions. This "gentle" decrease lowers the collision probability, especially when the competing node number is large. We compute the optimal value for c, and the numerical results from both analysis and simulation demonstrate that GDCF significantly improve the performance of 802.11 DCF including throughput, fairness, and energy efficiency. In addition, GDCF is flexible for supporting priority access by selecting different values of c for different traffic types; it is fully compatible with the original 802.11 DCF, and simple to implement, as it does not requires changes in control message structure and access procedures in DCF.
8899940
Sketch retrieval based on spatial relations
In this paper, we propose an effective approach for sketch retrieval. Given sketches are firstly decomposed into basic geometric primitives and represented as a topological graph that encodes both the intrinsic attributes of the primitives and their relationships. The graph spectrum descriptor is then adopted to translate the graph-match into the computation of vector distances. Sketches retrieval is finally done by means of similarity calculation of feature vectors based on dimensionality reduction. The relevance feedback is also introduced to refine the retrieval results. Experiments prove the effectiveness and efficiency of the proposed method in sketch content retrieval and user independent.
17395966
Scene segmentation based on video structure and spectral methods
Scene is an important semantic unit for video analysis, retrieval and browsing. However, due to the lack of a generic algorithm, many studies focus on specific methods for certain video genes, e.g., news, sports, etc. In this paper, we propose a general framework for scene segmentation. First, we construct a graph, in which the elements encode the shot-to-shot coherent characteristics of a video clip based on visual similarity and temporal relation between shots. In this step, we only exploit the inherent property of video itself and it is independent of video genres. Second, spectral method is applied on the graph to group shots into scenes. The proposed method is not only simple but also effective to deal with organized features. Experimental results validate the robustness of our method on different kinds of videos.
37868959
A Method of Raster Data Mining Based on Multi Dimension Data Set
Spatial Data Mining can mine automatically or semi-automatically unknown, creditable, effective, integrative or schematic knowledge which can be understood from the increasingly complex spatial database and enhance the ability of interpreting data to generate useful knowledge. There are large amounts of data existing in the database of Government GIS. However, a great deal of the data is idle, which has caused a huge waste of data due to rarely effectively utilization in practice. It is very necessary to deal with the task of data mining based on Government GIS. In this paper, an example on land utilization and land cover in a certain region of Guizhou Province was presented to describe the course of spatial data mining. There into, a derived star-type model was used to organize the raster data to form multi dimension data set. Under these conditions, clustering method was utilized to carry out data mining aiming at the raster data. Based on corresponding analyses, users can find out which types of vegetation were suitable for being cultivated in this region by using related knowledge in a macroscopic view. Therefore, feasible service information could be provided to promote economic development in the region.
29762263
Look-Ahead Scheme for High Speed Consecutive Micro Line Interpolation Based on Dynamics of Machine Tool
This paper presents a new look-ahead Scheme with adaptability of dynamics of machine tool for high speed consecutive micro-line interpolation. A backtracking arithmetic is used to calculate the speeds in the link points of consecutive micro-lines. Moreover, the speed limitations in the link points are analyzed in detail and the compound constraint conditions of the motion axes is introduced based the dynamic characteristics of machine tool. The case studies indicate that, using the scheme presented by this paper, the actual interpolation speed is closer to the command speed and the shock that results from the sharp fluctuate of feed speed is depressed, which will improve the machining efficiency and quality.