Recently, two-dimensional (2-D) signature patterns were proposed to encode binary digitized image pixels in optical code-division multiple-access (CDMA) networks with 'multicore' fiber. The new technology enables parallel transmission and simultaneous access of 2-D images in multiple-access environment, where these signature patterns are defined as optical orthogonal signature pattern codes (OOSPCs). However, previous work on OOSPCs assumed that the weight of each signature pattern was the same. In this paper, we construct a new family of OOSPCs with the removal of this assumption. Since varying the weight of a user's signature pattern affects that user's performance, this approach is useful for CDMA optical systems with multiple performance requirements.
We propose a joint source/channel coding scheme to transmit image through binary noisy channels based on 2-D discrete cosine transform (DCT) and trellis coded quantization (TCQ). When an image is transmitted through noisy channel with high throughput, both image compression and error-resilient coding scheme need to be considered. After the discrete cosine transform, the source image is decomposed into several subsources according to the transform coefficient positions, i.e., the same frequency coefficients in different DCT blocks are grouped together as a single subsource. The mean and variance values are used to construct the scalar codebooks for TCQ. Uniform threshold trellis coded quantizer is constructed to release the complexity and the transform coefficients are quantized by these fixed-rate quantizer and transmitted through noisy channels. No explicit error protection is used. The steepest descent method and iterative schemes are employed to determine the optimum bit allocation among the subsources subject to the constraints of the average coding rate and allowable maximum bits to each sample. Neighborhood relation is employed to limit the searching space when a bit is to be allocated to certain subsource. Simulation results show that the performance is very promising.
Multimedia data is isochronous in nature and entails managing and delivering high volumes of data. Multiprocessors with their large processing power, vast memory, and fast interconnects, are an ideal candidate for the implementation of multimedia applications. Initially, multiprocessors were designed to execute scientific programs and thus their architecture was optimized to provide low message latency and efficiently support regular communication patterns. Hence, they have a regular network topology and most use wormhole routing. The design offers the benefits of a simple router, small buffer size, and network latency that is almost independent of path length. Among the various multimedia applications, video on demand (VOD) server is well-suited for implementation using parallel multiprocessors. Logical models for VOD servers are presently mapped onto multiprocessors. Our paper provides a framework for calculating bounds on utilization of system resources with which QoS parameters for each isochronous stream can be guaranteed. Effects of the architecture of multiprocessors, and efficiency of various local models and mapping on particular architectures can be investigated within our framework. Our framework is based on rigorous proofs and provides tight bounds. The results obtained may be used as the basis for admission control tests. To illustrate the versatility of our framework, we provide bounds on utilization for various logical models applied to mesh connected architectures for a video on demand server. Our results show that worm hole routing can lead to packets waiting for transmission of other packets that apparently share no common resources. This situation is analogous to head-of-the-line blocking. We find that the provision of multiple VCs per link and multiple flit buffers improves utilization (even under guaranteed QoS parameters). This analogous to parallel iterative matching.
One way to efficiently combat channel errors is to employ unequal error protection (UEP) for information of different importance. The traditional approach to UEP through channel coding does not fully take advantage of the image signal properties. The high correlation nature of the image signal makes it possible to detect and correct many channel errors directly on the decoded image. Based on this observation, we propose in this paper a new approach which provides UEP through channel coding in a way seemingly contrast to traditional ones. Specifically, some good source detection/correction schemes are incorporated to detect/correct, directly on the decoded image, the noticeable damage which is often caused by channel errors affecting the important (in the view of tradition UEP schemes) data. With the help of source detectors, the problem of how to prioritize the transmitted data for channel protection is revisited and reformulated. We show that by intelligently combining unequal channel protection and source detection, both subjectively and objectively better quality of reconstructed images can be obtained. A general framework of the new approach is presented. Three case studies, including one for transmission of vector quantized images over noisy channels, one for a simplified fax coding system and the other one suggested by an intelligent block dropping approach, are examined.
We obtain network traffic model for real-time MPEG-II encoded digital video by analyzing video stream samples from real-time encoders from NUKO Information Systems. MPEG-II sample streams include a resolution intensive movie, City of Joy, an action intensive movie, Aliens, a luminance intensive (black and white) movie, Road To Utopia, and a chrominance intensive (color) movie, Dick Tracy. From our analysis we obtain a heuristic model for the encoded video traffic which uses a 15-stage Markov process to model the I,B,P frame sequences within a group of pictures (GOP). A jointly-correlated Gaussian process is used to model the individual frame sizes. Scene change arrivals are modeled according to a gamma process. Simulations show that our MPEG-II traffic model generates, I,B,P frame sequences and frame sizes that closely match the sample MPEG-II stream traffic characteristics as they relate to latency and buffer occupancy in network queues. To achieve high multiplexing efficiency we propose a traffic shaping scheme which sets preferred 1-frame generation times among a group of encoders so as to minimize the overall variation in total offered traffic while still allowing the individual encoders to react to scene changes. Simulations show that our scheme results in multiplexing gains of up to 10% enabling us to multiplex twenty 6 Mbps MPEG-II video streams instead of 18 streams over an ATM/SONET OC3 link without latency or cell loss penalty. This scheme is due for a patent.
The objective behind transform coding is to transform a data array into a statistically uncorrelated set. The uneven distribution of energy in transform coefficients is exploited for compression purposes, with significant energies considered for further processing. Block transforms, particularly the discrete cosine transform, have been used in image-video coding. An approximate Fourier expansion (AFE) of non-periodic signals with theoretically uncorrelated coefficients has been previously proposed. Furthermore, the capabilities of an approximate cosine expansion (ACE) have been explored for purposes of image coding. In this paper, we apply an approximate trigonometric expansion to images and investigate the potential of adaptive coding using blocks of images. The variable length basis functions computed by varying a user-defined parameter of the expansion will be used for adaptive transform coding of images. For comparison purposes, the results are compared with discrete cosine transform (DCT). Computer simulation results also are presented.
The standard discrete wavelet transform lacks translation invariance in 1-D signals and 2-D images. The down-sampling at each coarser scale accentuates the undesirable effects of the shift-variance, in particular, on the motion estimation from decomposed subimages in video coding. In this paper, we present a study of applying the Chui-Shi shift-invariant wavelet transform using 'oversampling frames' to video compression. Further, we present an algorithm for approximating the motion fields at different scales and different frequency bands by utilizing the multiresolution structure of wavelet decomposition. Motion vectors at a higher resolution are predicted by the motion vectors at a lower resolution through a proper scaling. Experimental results on a salesman video sequence show that the use of the 2-D oversampling algorithm of a biorthogonal spline wavelet has reduced the required number of motion vectors while maintaining an acceptable prediction error when compared to the classical block matching technique using the standard wavelet transform. The proposed approach will advance the video compression methodology for applications to HDTV and video conferencing.
This paper describes a contour-based representation of images. More particularly, we discuss a method of representing image data which is a resolution-independent scheme and can provide an interactive viewing capability for every user. In this method, a two dimensional (x,y) image is regarded as a curved surface in a three dimensional space having luminance/chrominance value of an image measured along z-axis. And an image is represented using contour lines which are contours of cross-sectional areas made by slicing a curved surface perpendicularly through z-axis. We also discuss a scheme for reconstructing images based on the proposed contour-based representation. Within the framework of image representation, contour lines are stored in a vector-coded format which is independent of the pixel resolution. Consequently a scalable representation algorithm can be realized, and it is possible to reconstruct image in quality which is in compliance with various kinds of user's requests.
This paper presents a technique to segment and track a region of interest in a video sequence. The presented technique starts with a spatio-temporal contour extraction. This contour extraction is performed by mixing information from a spatial gradient and a temporal differentiator. A block segmentation is then applied on the image, and within each block the contour part is approximated by a straight line segment. These contour approximations are then further quantized by a vector quantization technique, using a predefined codebook. In order to close and smooth the region of interest contour, an interpolation based on hermite polynomials is performed on the set of discrete quantized contour parts. Finally, the tracking process is performed using an addition-removal of blocks containing contour parts by testing their possible belonging to the polynomial contour. This testing is done by using a blurred version of the polynomial contour in order to be able to track deformations in the object. The initial guess for tracking is given manually by an end-user.
With the increase in the number of digital networks and recording devices, digital images appear to be a material, especially still images, whose ownership is widely threatened due to the availability of simple, rapid and perfect duplication and distribution means. It is in this context that several European projects are devoted to finding a technical solution which, as it applies to still images, introduces a code or watermark into the image data itself. This watermark should not only allow one to determine the owner of the image, but also respect its quality and be difficult to revoke. An additional requirement is that the code should be retrievable by the only mean of the protected information. In this paper, we propose a new scheme based on fractal coding and decoding. In general terms, a fractal coder exploits the spatial redundancy within the image by establishing a relationship between its different parts. We describe a way to use this relationship as a means of embedding a watermark. Tests have been performed in order to measure the robustness of the technique against JPEG conversion and low pass filtering. In both cases, very promising results have been obtained.
REmote authentication is vital for many network based applications. As the number of such applications increases, user friendliness of the authentication process, particularly as it relates to password management, becomes as important as its reliability. The multimedia capabilities of the modern terminal equipment can provide the basis for a dependable and easy to use authentication system which does not require the user to memorize passwords. This paper outlines our implementation of an authentication system based on the joint use of the speech and facial video of a user. Our implementation shows that the voice and the video of the associated lip movements, when used together, can be very effective for password free authentication.
The Research Data Network Cooperative Research Center is conducting trials over an experimental city-to-city asynchronous transfer mode (ATM) network as part of an initiative to investigate potential applications of high- speed switched networks. One of these trials involves the remote access and navigation of video collections by film and television researchers and is being conducted to investigate the architectural design and implementation issues of such a system. The trial involves several Australian film and television archives and archive users who normally search through footage from remote archives as part of the process of film or television production. FRANK (the film/TV researchers archival navigation kit) is the software developed for the trial that provides a tight integration between video playback and the searching and navigation through alternate representations of the video such as transcripts and shotlists that may reside on different locations on the network.
This paper is centered on the description of a model that generalizes multimedia data flows handling including complete behavior and interaction mechanisms, hence allowing full integration of GUIs generation -- GUI components are upgraded to interactive media items -- into the same unified model. It aims to reinforce portability, reusability, and quick development of multimedia applications. A picture of previous and of current state-of-art in multimedia application development clearly shows the need for standard abstractions in this field. Current work in this direction leads to a discussion on generic application structure (objects, semantics, etc.) and on different approaches to reach platform independence and efficient object sharing (formal representation languages, interpreted programming languages, distributed environments, etc.). At this point, we present a basic model based on several stream-based models and implementations on multimedia data flows, and built on the basis of the source-stream-sink paradigm. It follows with a detailed explanation of the unified (common to all media) abstract basic stream from which all monomedia flows (including GUI elements) are derived: stream setting- up (source-sink adaptation, and negotiation), flow control procedure, stream sensibility, behavior pattern, etc. The model presentation ends up with the introduction of the multimedia stream that performs synchronization and inter- stream communication tasks, and channels all sensibility, from/towards its managed streams, and allows for the design of an application generator. Then it deeps into the definition of the abstract class hierarchy that guides the model implementation. Finally, several implementation issues are addressed and some practical achievements are described.
A core system architecture is proposed following a functional model that separates the application subsystem into three functional groups, namely hypermedia, management, and communication, and provides an application development support system. This architecture provides access to storage systems (information provision engines) independently of their internal per site structure. Once the core system building blocks are available at the information provider sites, different applications can be easily developed on top of the functional services provided by the core system. These applications, although using the same core system, will be different in the way the functionalities are provided to the users, as they may have quite different requirements in how they want to search, use information, present, customize, collaborate, etc.
Network-based multi-user interaction systems such as network games typically include a database shared among the players that are physically distributed and interact with one another over the network. Currently network game developers have to implement the shared database and the inter-player communications from scratch. This paper presents the result of a performance study on the effects of network bandwidth optimization techniques provided by a previously proposed distributed system, Artery, which is specifically designed to support network game applications by providing high-level application program interfaces and by exploiting application semantics for traffic reduction. This work studied a popular public-domain network game called Netrek, and showed through experiments that the techniques proposed in Artery combined can indeed cut down the network bandwidth requirements of Netrek sessions by a factor between 5 to 90, depending on the number of players in the game.
Internet firewalls control the data traffic in and out of an enterprise network by checking network packets against a set of rules that embodies an organization's security policy. Because rule checking is computationally more expensive than routing-table look-up, it could become a potential bottleneck for scaling up the performance of IP routers, which typically implement firewall functions in software. in this paper, we analyzed the performance problems associated with firewalls, particularly packet filters, propose a good connection cache to amortize the costly security check over the packets in a connection, and report the preliminary performance results of a trace-driven simulation that show the average packet check time can be reduced by a factor of 2.5 at the least.
This paper describes the design, implementation, and evaluation of a broadcast trivial file transfer (BTFTP) protocol, which can be used as an efficient data transport protocol for networks that inherently support hardware broadcasting, such as Ethernet, wireless LANs, and cable TV networks. We show that BTFTP out-performs FTP on an Ethernet environment when there are more than two clients, and the performance difference increases as the number of clients increases.
This paper presents interactive multimedia database (IMDB) which makes image processing possible on World Wide Web (WWW). It is different from typical image database to provide only storage and retrieval function of image data. The higher performance of electronic parts such as a transistor, the inner structure becomes more complicated. Non-destructive evaluations of the high-precision electronic parts are necessary to maintain the quality. As the first approach, we visualize inside state of electronic parts as two or three-dimensional images with x-ray CT (computerized tomography), and we aim at the efficiency of non-destructive test by registering these images with database. IMDB provides cross section of electronic parts, and three- dimensional visualization from various angles, and animation to support the test of defects. The point we want to make is that this database is different from current client/server type database that retrieval function is main function, and IMDB enables users to process image such as edge extraction on WWW network. In addition to CT image, IMDB receives various images filmed with digital camera and image scanner from users, and executes the request of image processing and show the results.