Domain decomposition for variational optical-flow computation.

We present an approach to parallel variational optical-flow computation by using an arbitrary partition of the image plane and iteratively solving related local variational problems associated with each subdomain. The approach is particularly suited for implementations on PC clusters because interprocess communication is minimized by restricting the exchange of data to a lower dimensional interface. Our mathematical formulation supports various generalizations to linear/nonlinear convex variational approaches, three-dimensional image sequences, spatiotemporal regularization, and unstructured geometries and triangulations. Results concerning the effects of interface preconditioning, as well as runtime and communication volume measurements on a PC cluster, are presented. Our approach provides a major step toward real-time two-dimensional image processing using off-the-shelf PC hardware and facilitates the efficient application of variational approaches to large-scale image processing problems.     

A new approach to authentication of binary images for multimedia communication with distortion reduction and security enhancement

A new approach to binary image authentication in multimedia communication with distortion reduction and security enhancement is proposed. Special codes are embedded into the blocks of given images and verified to accomplish the authentication purpose. Enhancement of security in detecting tampered images is achieved by randomly generating the codes and embedding them into randomly selected locations in the image blocks. The reduction of image distortion coming from pixel value replacement in code embedding is carried out by allowing multiple locations for embedding the codes. Security analysis and experimental results are also included to show the effectiveness of the proposed approach.     

基于非对称数据结构实现信息隐藏通信的方法研究

 数据结构是影响信息隐藏通信实时性能的关键技术.为此,系统设计需要对信源统计、信道状态与传输码率之间进行折衷考虑.按照信息隐藏通信的要求,把信源的统计特性以边信息在解码端进行处理,本文提出了一种非对称数据结构实现信息隐藏通信的方法.结合图像系数的方差分布和不同WNR环境下的信道状态,该方法能够降低了系统编解码实现的复杂性.分别应用SCS和QIM(DC-DM)及SS技术,结果表明,该方法实现的通信系统都具有较好的折衷性能.     

On color transforms and bit allocation for optimal subband image compression

Although subband transform coding is a useful approach to image compression and communication, the performance of this method has not been analyzed so far for color images, especially when the selection of color components is considered. Obviously, the RGB components are not suitable for such a compression method due to their high inter-color correlation. On the other hand, the common selection of YUV or YIQ is rather arbitrary and in most cases not optimal. In this work we introduce a rate–distortion model for color image compression and employ it to find the optimal color components and optimal bit allocation (optimal rates) for the compression. We show that the DCT (discrete cosine transform) can be used to transform the RGB components into an efficient set of color components suitable for subband coding. The optimal rates can be also used to design adaptive quantization tables in the coding stage with results superior to fixed quantization tables. Based on the presented results, our conclusion is that the new approach can improve presently available methods for color image compression and communication.     

无线数字图像通信关键技术研究

文中研究了无线数字图像通信关键技术,采用理论结合实践的方法,立足无线数字图像通信的概念和技术特点,分析了无线数字图像通信技术的研究现状,并分析了实现无线数字图像通信的关键技术以及无线数字图像传输过程中的差错控制方法。研究结果表明,无线数字图像通信是一种新型的通信技术,可实现图像的有效、快速、安全传输,加强对无线数字图像通信关键技术的分析与研究,有利于促进该技术的持续、稳定发展。     

Efficient Image Transmission with Multi-Carrier CDMA

This paper presents a new approach for efficient image transmission over Multi-Carrier Code Division Multiple Access (MC-CDMA) systems using chaotic interleaving. The chaotic interleaving scheme based on Baker map is applied on the image data prior to transmission. The proposed approach transmits images over wireless channels, efficiently, without posing significant constraints on the wireless communication system bandwidth and noise. The performance of the proposed approach is further improved by applying Frequency-Domain Equalization (FDE) at the receiver. Two types of frequency-domain equalizers are considered and compared for performance evaluation of the proposed MC-CDMA system; the Zero-Forcing equalizer and the Linear Minimum Mean Square Error (LMMSE) equalizer. Several experiments are carried out to test the performance of the image transmission with different sizes over the proposed MC-CDMA system. Simulation results show that image transmission over wireless channels using the proposed chaotic interleaving approach is much more immune to noise and fading. Moreover this chaotic interleaving process adds a degree of encryption to the transmitted data. The results also show a noticeable performance improvement in terms of the Root Mean Square Error and Peak Signal-to-Noise Ratio values when applying FDE in the proposed approach, especially with the LMMSE equalizer.     

Blind quality assessment of image and video based on fragile watermarking and robust features

Blind quality assessment is an important feature required by many modern multimedia communication systems. Reduced reference approaches employing fragile watermarking techniques have been proposed earlier for this purpose. This paper proposes an approach which makes use of robust image features and fragile watermarking techniques resulting in a reduced reference strategy. Other than the input image, the approach requires no external information. Robust image features are used to construct the watermark from the image to be transmitted, which is then embedded as a fragile watermark in the image itself. The same features are once again used to construct the reference watermark from the received image, with which the extracted fragile watermark is compared to determine the amount of degradation suffered by it. Construction of the watermark from the image itself, dispenses with the need for embedding an extraneous watermark which must be made known to the user separately. Singular Value Decomposition is used for the extraction of the fragile watermark from the received image while a different approach is used for reduced reference quality assessment of video sequences, making use of consecutive video frames. These form the significant contributions of the present work. The performances of the proposed algorithms have been demonstrated through extensive simulations using different kinds of gray-scale and color images and a number of popularly used test video sequences.

     

基于ARM的实时图像采集压缩系统设计与实现

针对系统低功耗的实际需求,提出一种基于ARM的嵌入式图像采集压缩系统的实现方案.采用一片CPLD设计时序控制器,很好地解决了图像采集系统存在的系统严格同步和高速数据流实时处理的设计难点,并能实现ARM及其外围器件之间的控制逻辑和数据交互.详细介绍了系统硬件平台的构建及系统软件的设计流程,并给出实验结果.利用本系统能够在远程PC的控制下实时采集压缩图像,并通过无线传感网络传输,系统功耗低于200 mW.     

Vessel extraction under non-uniform illumination: a level set approach

Vessel extraction is one of the critical tasks in clinical practice. This communication presents a new approach for vessel extraction using a level-set-based active contour by defining a novel local term that takes local image contrast into account. The proposed model not only preserves the performance of the existing models on blurry images, but also overcomes their inability to handle nonuniform illumination. The efficacy of the approach is demonstrated with experiments involving both synthetic images and clinical angiograms.     

Technologies du tatouage pour l’authentification et la protection des images

This paper overviews image watermarking techniques and their integration into protection systems. It is shown how that technology can solve the problems of waveform authentication as well as those related to tracing of digital copies. Image processing techniques and the communication system of watermarking are briefly presented. Some challenges approach to the watermarking field are enumerated in the conclusion.     

Joint Source-Channel Distortion Modeling for MPEG-4 Video

Multimedia communication has become one of the main applications in commercial wireless systems. Multimedia sources, mainly consisting of digital images and videos, have high bandwidth requirements. Since bandwidth is a valuable resource, it is important that its use should be optimized for image and video communication. Therefore, interest in developing new joint source-channel coding (JSCC) methods for image and video communication is increasing. Design of any JSCC scheme requires an estimate of the distortion at different source coding rates and under different channel conditions. The common approach to obtain this estimate is via simulations or operational rate-distortion curves. These approaches, however, are computationally intensive and, hence, not feasible for real-time coding and transmission applications. A more feasible approach to estimate distortion is to develop models that predict distortion at different source coding rates and under different channel conditions. Based on this idea, we present a distortion model for estimating the distortion due to quantization and channel errors in MPEG-4 compressed video streams at different source coding rates and channel bit error rates. This model takes into account important aspects of video compression such as transform coding, motion compensation, and variable length coding. Results show that our model estimates distortion within 1.5 dB of actual simulation values in terms of peak-signal-to-noise ratio.      

基于Karhunen-Loeve变换和最低位替代的图像隐写术

为了提高信息通信安全性能,防止信息被窃取,提出了一种新颖的图像隐写术.采用Karhunen-Loeve变换压缩数据,构造其最低位替代加密数据,并在载体图像内对信息进行编码,其压缩过程用于去除冗余性,同时还设计了编码到一个级别的像素矩阵,由最低位替换的方式进一步实施.实验结果表明,该算法效率高,并能对原始数据进行有效的解密;且与其他机制相比,所提出的技术具有更高的容量和平均信噪比.     

Hybrid image/ray-shooting UHF radio propagation predictor forpopulated indoor environments

A novel model for indoor wireless communication, based on a dual image and ray-shooting approach, is presented. The model, capable of improved site-specific indoor propagation prediction, considers multiple human bodies moving within the environment. In a modern office at 2.45 GHz, the combined effect of pedestrian traffic and a moving receiver causes rapid temporal fading of up to 30 dB     

Satellite‐PCS channel simulation in mobile user environments using photogrammetry and Markov chains

In this paper, we present a system that models the land‐mobile satellite communication channel with a Markov chain approach supported by images of the mobile Earth station's (MES) environment. Our method employs a video camera with a fish‐eye lens capturing image sequences of the user environment from the position of the moving MES, image and signal processing algorithms to recognize propagation path states and extract their duration and transition probabilities, and modeling of the communication channel characteristics using the theory of Markov stochastic processes combined with statistical fade distributions appropriate for given path states. The results demonstrate that the procedure provides a full statistical characterization of the narrow‐band land‐mobile satellite propagation channel in several environments. This revised version was published online in June 2006 with corrections to the Cover Date.     

基于塔式格型矢量量化的图像多描述编码算法

多描述编码(MDC)是解决差错信道上图像通信数据包丢失问题的一种新方法，它通过将图像分解为多个独立而又具有一定相关性的描述，并通过不同的信道进行传输，来改善数据丢失条件下的图像解码质量。本文提出了一种图像信号的多描述塔式格型矢量量化编码算法(MDPLVQ)，利用小波树之间的独立性，采用不同的塔式格型矢量量化缩放因子对小波系数进行量化。该算法设计简单，对冗余度的控制容易，实验结果说明了其有效性，其编码压缩性能优于多描述标量量化(MDSQ)、多描述对变换(MDPCT)和多描述零又树(MDEZW)等方法。     

A new approach in content-based image retrieval using fuzzy

Finding an image from a large set of images is an extremely difficult problem. One solution is to label images manually, but this is very expensive, time consuming and infeasible for many applications. Furthermore, the labeling process depends on the semantic accuracy in describing the image. Therefore many Content based Image Retrieval (CBIR) systems are developed to extract low-level features for describing the image content. However, this approach decreases the human interaction with the system due to the semantic gap between low-level features and high-level concepts. In this study we make use of fuzzy logic to improve CBIR by allowing users to express their requirements in words, the natural way of human communication. In our system the image is represented by a Fuzzy Attributed Relational Graph (FARG) that describes each object in the image, its attributes and spatial relation. The texture and color attributes are computed in a way that model the Human Vision System (HSV). We proposed a new approach for graph matching that resemble the human thinking process. The proposed system is evaluated by different users with different perspectives and is found to match users’ satisfaction to a high degree.     

从图像通信的发展看数字通信技术的发展趋势

21世纪,随着经济技术的发展,话音业务逐渐饱和,数据业务增长迅速,人们对以图像通信为主的多媒体视频业务的需求越来越强烈。随着宽带通信网络、计算机网络、3G、无线城域网等的进一步发展,图像通信业务的市场需求更加广泛。以数字图像通信为主的图像通信业务将逐渐成为继话音、数据业务之后的第三种基本通信业务,并广泛服务于诸多领域。面对市场导引、技术推动下的图像通信业务发展,本文将从几个方面展望未来数字通信技术的发展前景。     

Portable video-on-demand in wireless communication

Our present ability to work with video has been confined to a wired environment, requiring both the video encoder and decoder to be physically connected to a power supply and a wired communication link. This paper describes an integrated approach to the design of a portable video-on-demand system capable of delivering high-quality image and video data in a wireless communication environment. The discussion will focus on both the algorithm and circuit design techniques developed for implementing a low-power video compression/decompression system at power levels that are two orders of magnitude below existing solutions. This low-power video compression system not only provides a compression efficiency similar to industry standards, but also maintains a high degree of error tolerance to guard against transmission errors often encountered in wireless communication. The required power reduction can best be attained through reformulating compression algorithms for energy conservation. We developed an intra-frame compression algorithm that requires minimal computation energy in its hardware implementations