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The idea of embedding some information within a digital media, in such a way that the inserted data are intrinsically part of the media itself, has aroused a considerable interest in different fields. One of the more examined issues is the possibility of hiding the highest possible amount of information without affecting the visual quality of the host data. For such a purpose, the understanding of the mechanisms underlying Human Vision is a mandatory requirement. Hence, the main phenomena regulating the Human Visual System will be firstly discussed and their exploitation in a data hiding system will be then considered. INTRODUCTION In the last 10 years, digital watermarking has received increasing attention, since it is seen as an effective tool for copyright protection of digital data (Petitcolas, Anderson, & Kuhn, 1999), one of the most crucial problems slowing down the diffusion of new multimedia services such as electronic commerce, This chapter appears in the book, Multimedia Security: Steganography and Digital Watermarking Techniques for Protection of Intellectual Pro erty, edited by Chun-Shien Lu. Copyright © 2005, Idea Group Inc. Copying or distributing in print or electronic forms without written permission of Idea Group Inc. is prohibited. 701 E. Chocolate Avenue, Suite 200, Hershey PA 17033-1240, USA Tel: 717/533-8845; Fax 717/533-8661; URL-http://www.idea-group.com IDEA GROUP PUBLISHING Perceptual Data Hiding in Still Images 49 Copyright © 2005, Idea Group Inc. Copying or distributing in print or electronic forms without written permission of Idea Group Inc. is prohibited. open access to digital archives, distribution of documents in digital format and so on. According to the watermarking paradigm, the protection of copyrighted data is accomplished by injecting into the data an invisible signal, that is, the watermark, conveying information about data ownership, its provenance or any other information that can be useful to enforce copyright laws. Recently, the idea of embedding some information within a digital document in such a way that the inserted data are intrinsically part of the document itself has been progressively applied to other purposes as well, including broadcast monitoring, data authentication, data indexing, content labelling, hidden annotation, and so on. Regardless of the specific purpose, it is general agreed that one of the main requirements a data hiding scheme must satisfy regards invisibility; that is, the digital code must be embedded in an imperceptible way so that its presence does not affect the quality of the to-be-protected data. As far as the embedding of a hidden signal within a host image is concerned, it is evident that the understanding of the mechanisms underlying human vision is a mandatory requirement (Cox & Miller, 1997; Tewfik & Swanson, 1997; Wolfgang, Podilchuk, & Delp, 1999). All the more that, in addition to the invisibility constraint, many applications require that the embedded information be resistant against the most common image manipulations. This, in turn, calls for the necessity of embedding a watermark whose strength is as high as possible, a task which clearly can take great advantage from the availability of an accurate model to describe the human visual system (HVS) behaviour. In other words, we can say that the goal of perceptual data hiding is twofold: to better hide the watermark, thus making it less perceivable to the eye, and to allow to the use of the highest possible watermark strength, thus influencing positively the performance of the data recovery step. Many approaches have been proposed so far to model the characteristics of the HVS and to exploit such models to improve the effectiveness of existing watermarking systems (Podilchuk & Zeng, 1998; Wolfgang et al., 1999). Though all the proposed methods rely on some general knowledge about the most important features of HVS, we can divide the approaches proposed so far into theoretical (Kundur & Hatzinakos, 1997; Podilchuk & Zeng, 1998; Swanson, Zhu, & Tewfik, 1998; Wolfgang et al., 1999) and heuristic (Bartolini, Barni, Cappellini & Piva, 1998; Delaigle, Vleeschouwer, & Macq, 1998; Van Schyndel, Tirkel, & Osborne, 1994) ones. Even if a theoretically grounded approach to the problem would be clearly preferable, heuristic algorithms sometimes provide better results due to some problems with HVS models currently in use (Bartolini, 1998; Delaigle, 1998). In this chapter, we will first give a detailed description of the main phenomena regulating the HVS, and we will consider the exploitation of these concepts in a data hiding system. Then, some limits of classical HVS models will 25 more pages are available in the full version of this document, which may be purchased using the "Add to Cart" button on the publisher's webpage: www.igi-global.com/chapter/perceptual-data-hiding-stillimages/27045

The recent finalization of MPEG-4 will make this standard very attractive for a large range of applications such as video editing, Internet video distribution, wireless video communications. Some of these applications are likely to get great benefit from watermarking technology, since it can enable a number of innovative services, such as conditional access policies, data annotation, data labeling, content authentication, to be implemented at a low price. One of the key points of the MPEG-4 standard is the possibility to access and manipulate objects within a video sequence. Thus object watermarking has to be achieved in such a way that, while a video object is transferred from a sequence to another, it is still possible to correctly access the data embedded within the object itself. The algorithm proposed in this paper embeds a watermark in each video object by imposing a particular relationship between some predefined pairs of quantized discrete cosine transform (DCT) coefficients in the luminance blocks of pseudo-randomly selected macroblocks (MBs). Watermarks are equally embedded into intra and inter MBs. Experimental results are presented validating the effectiveness of the proposed approach.

In this paper an objective metric to measure the perceptual quality of watermarked 3D meshes is presented. The metric, which is based on a black-box approach, relies on the measurement of the roughness of 3D meshes before and after the insertion of the watermark. To calibrate the metric and to validate it, a set of psychovisual experiments has been carried out. Due to the lack of prior work in this field, a new methodology for the subjective evaluation of the quality of watermarked 3D objects is introduced. The validity of the proposed metric has been tested against a number of different 3D watermarking algorithms, showing an excellent match with the subjective evaluation of the quality stemming from the pshycovisual experiments.

A novel quantization-based data-hiding method, called Rational Dither Modulation (RDM), is presented. This method retains most of the simplicity of the conventional dither modulation (DM) scheme, which is largely vulnerable to amplitude scalings and modifies it in such a way that the result becomes invariant to gain attacks. RDM is based on using a gain-invariant adaptive quantization step-size at both embedder and decoder. This causes the watermarked signal to be asymptotically stationary. Mathematical tools are used to determine the stationary probability density function, which is later used to assess the performance of RDM in Gaussian channels. It is also shown that by increasing the memory of the system, it is possible to asymptotically approach the performance of DM, still keeping invariance against gain attacks. RDM is compared with improved spread-spectrum methods, showing that the former can achieve much higher rates for the same bit error probability. Experimental results confirm the validity of the theoretical analyses given in the paper. Finally, a broader class of methods, that extends gain-invariance to quantization index modulation (QIM) methods, is also presented.

In remote sensing systems, on-board data compression is a crucial task that has to be carried out with limited computational resources. In this paper we propose a novel lossless compression scheme for multispectral and hyperspectral images, which combines low encoding complexity and high-performance. The encoder is based on distributed source coding concepts, and employs Slepian-Wolf coding of the bitplanes of the CALIC prediction errors to achieve improved performance. Experimental results on AVIRIS data show that the proposed scheme exhibits performance similar to CALIC, and significantly better than JPEG 2000.

In the last years the applications using and managing 3D data are quickly increasing: archaeological site reproduction, virtual museums (in the field of Cultural Heritage); games, animations, special effects (in the field of entertainment); enhanced user navigation, e-commerce, virtual reality (in Internet) are only some examples of the potentialities of such data. In this evolving scenario the demand for IPR protection of this kind of multimedia data is growing and new interest is moving towards 3D watermarking. This paper discusses some issues on 3D watermarking, such as robustness and visual quality, and presents a panoramic on some 3D watermarking models proposed so far. Regarding the visual quality aspect, a novel solution to reduce the perceptibility of the watermark, embedded through vertices perturbations is proposed.

Introduction Applications c Information Coding Data Embedding Data Concealment Data Recovery Watermark Impairments and Benchmarking Security Issues An Information Theoretic Perspective Bibliography Index.

Despite the increasing interest in digital watermarking of multimedia data, watermarking of 3D geometrical models has received little attention by the research community. One of the main reasons is that geometric data is intrinsically complex to handle, in addition a lot of diverse attacks can be thought of that are not possible in the 2D and 1D cases. So it is very difficult to develop robust watermarking algorithms for 3D models. In order to overcome the above problems most of the systems proposed so far exploit the knowledge of the original, non marked, mesh for watermark recovery. The practical usefulness of non-blind schemes, though, is very limited, hence the need to develop new blind schemes for 3D watermarking. In this paper we propose a blind watermarking algorithm for 3D meshes. Watermarking is achieved by perturbing the position of the vertices of the model according to a spherical pseudo-random bumped surface. The pseudo-random position and amplitude of the bumps encode the watermark. In order to gain robustness while keeping the distortion to a minimum, the watermark is embedded into a low resolution version of the mesh. The coarse version of the model is obtained by a MAPS1 (Multiresolution Adaptive Parameterization of Surface) algorithm. The base domain produced by this algorithm is used to obtain the full resolution watermarked model from the coarse watermarked one. Watermark recovery is accomplished by means of a standard correlation detector. Experimental results show that the system assure high visual quality of the watermarked model, and that a good degree of robustness can be reached for models with a suffciently high number of faces.

The performance of multiplicative spread spectrum watermarking algorithms are investigated under the simplifying assumption that host features are normally distributed, and attacks take the form of normally distributed additive noise. By relying on the obtained results, multiplicative spread spectrum watermarking is compared to its additive counterpart and to quantization based schemes.

The application of digital watermarking to remote sensing images requires a careful quality assessment in order to understand how the data quality is affected by the watermark. We propose a watermarking approach that minimizes the watermark impact on image classification, based on the idea of modulating the insertion coefficient in each channel so as to preserve to a larger extent the channels which classification is most sensitive to; we also propose a simplified procedure for estimating cluster displacement due to watermarking, leading to a low-complexity insertion approach. Experimental results on Landsat 7 ETM+ and IKONOS images show that the proposed MIC approach is able to significantly reduce classification errors, and to keep them within the intrinsic classification error

The performance of spread-transform dither modulation (ST-DM) watermarking in the presence of two important classes of non additive attacks, such as the gain attack plus noise addition, and the quantization attack are evaluated. The analysis is developed under the assumption that the host features are independent and identically distributed Gaussian random variables, and that a minimum distance criterion is used to decode the hidden information. The theoretical bit-error probabilities are derived in closed form, thus permitting to evaluate the impact of the considered attacks on the watermark at a theoretical level. The analysis is validated by means of extensive Monte Carlo simulations. In addition to the validation of the theoretical analysis, Monte Carlo simulations permitted to abandon the hypothesis of normally distributed host features, in favor of more realistic models adopting a Laplacian or a generalized Gaussian probability density function. The general result of our analysis is that the excellent performance of ST-DM are confirmed in all cases with the only noticeable exception of the gain attack.

The goal of this paper is to present the research that has been carried out over the last 10 years in the Image Processing and Communications Lab of the University of Florence for developing applications for the cultural heritage field. In particular research has focused on the following issues: high resolution acquisition of paintings by means of mosaicing techniques, colour calibration of the acquisition devices, tools for forecasting the results of restoration processes (in particular with reference to the cleaning process), systems for producing virtually restored digital copies of paintings (in particular for filling in cracks and lacunas). The problems related to the distribution of the digital copies have also been considered, in particular with reference to the watermarking of the images for copyright protection. The methodologies developed by the Lab with reference to the above mentioned issues will be described, and the main results discussed.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

In this paper a new approach for describing human visual system behavior is presented and its application for the quality evaluation of art images is described. In particular an automatic system which permits to determine when a disturbance is perceptible to the human eye is developed.

The progress of electronic imaging has encouraged the development of new tools for cultural heritage applications. In this paper some software, ArtShop, is described that contains tools for artwork image restoration, developed over several years of research.

In the last few years, digital watermarking has been proposed as a solution to the problem of copyright protection of multimedia data against unauthorized uses. In the field of image watermarking, research has been mainly focused on grey-scale image watermarking, whereas the extension to the color case is usually accomplished by marking the image luminance, or by processing each color channel separately. In this paper, a DCT domain technique expressly devised for watermarking of color images is presented, which exploits the characteristics of the human visual system and the correlation between the RGB image channels. Experimental results are presented to demonstrate the validity of the new approach with respect to algorithms operating on image luminance only.

This work addresses the problem of optimum decoding and detection of a multibit, multiplicative watermark hosted by Weibull-distributed features: a situation which is classically encountered for image watermarking in the magnitude-of-DFT domain. As such, this work can be seen as an extension of the system described in a previous paper, where the same problem is addressed for the case of 1-bit watermarking. The theoretical analysis is validated through Monte Carlo simulations. Although the structure of the optimum decoder/detector is derived in the absence of attacks, some experimental results are also presented, giving a measure of the overall robustness of the watermark when attacks are present.

The future development of networked multimedia services is conditioned by the achievement of efficient methods to grant that the Intellectual Property Rights (IPR) are well respected and the assets properly managed. In the framework of digital watermarking for the copyright protection of multimedia data, the specific case of video watermarking will be considered. In particular three different approaches for embedding a code in the video domain will be deeply described, and a particular attention will be focused on watermarking of MPEG-4 objects. Specific characteristics, advantages and drawbacks of the different systems will be highlighted.

Advances in electronic imaging over recent years have encouraged the development of newtools for cultural heritage applications. In this paper a software application called ArtShopis described, containing some tools for artwork image restoration, developed during severalyears of research at the Image and Communications Laboratory of the University ofFlorence. Copyright # 2003 John Wiley & Sons, Ltd.Received: 10 January 2003; Revised: 19 March 2003

The analysis of the security of watermarking algorithms has received increasing attention since it has been recognized that the sole investigation of robustness issues is not enough to properly address the challenges set by practical applications. Such a security analysis, though, is still in its infancy, up to a point that a general agreement has not yet been reached even on the most fundamental problems. The purpose of this paper is to provide a general security framework encompassing most of the problems encountered in real-world applications. By considering the amount of information the attacker has about the watermarking algorithm, we introduce the notion of fair and un-fair attacks, so to ease the classification of different systems and attacks. Though we recognize that many important differences exist between watermarking and cryptographic security, a large part of our work is inspired by the Diffie-Helmann's paradigm, which is widely used in cryptography. For each class of systems great care is taken to describe both the attacker's and watermarker's point of view, presenting the challenges raised by each system to these different actors. Finally, we try to outline some research directions which, according to us, deserve further analysis.

The unsupervised detection of an unknown number of straight lines in digital imagery is addressed. Based on possibilistic clustering an algorithm is proposed which does not require any assumption about the number of straight lines present in the edge map. Three major modifications are introduced with respect to existing clustering-based algorithms: the use of possibilistic clustering; a more sophisticated analysis of the clusters, including the possibility of rejecting non linear clusters; a bottom up strategy to evaluate how many straight lines the image contains. The effectiveness of the proposed scheme is proved by validating it against real world imagery.

In the field of video coding the issues of backward prediction and standards conversion have focused an increasing attention towards techniques for an effective estimation of the true interframe motion. The problem of restoration of motion vector-fields computed by means of a standard block matching algorithm is addressed. The restoration must be carried out carefully by exploiting both the spatial correlation of the vector-field, and the significance of the obtained vectors as measures of the reliability of the previous estimation step. A novel approach matching both the above requirements is presented. Based on the theory of vector-median filters an adaptive scheme is developed and results are discussed.

For reducing impulsive noise without degrading image contours, median filtering is a powerful tool. In multiband images, as for example color images or vector field obtained by optic flow computation, a vector median filter can be used. Vector median filters are defined on the basis of a suitable distance, the best performing distance being the Euclidean. The Euclidean distance is computed by using the Euclidean norm which is quite demanding from the point of view of computation given that a square root is required. An optimal piecewise linear approximation of the Euclidean norm is presented which is applied to vector median filtering.

Modern manufacturing systems call for full-rate automated inspection of produced samples. A vision-based intelligent perception system (IPS) is presented making automated inspection of chicken meat feasible. The IPS analyzes RGB images framing the chickens after the slaughtering and plucking process and detects defects such as burns, hematomas and blisters, along with other relevant features. The vision module, which is the core of the system, operates by first extracting the chicken body from the background, then it segments the body into its anatomic subparts. Defective areas are identified by means of morphological reconstruction. Finally, defects are classified by comparing their features against the defect description contained in a reference database.

A three-step algorithm is developed to segment oil spills from a marine background on synthetic aperture radar (SAR) data. First, filtering is performed to reduce speckle noise. Then fuzzy clustering is carried out to obtain a preliminary partition of the pixels on the basis of their grey level intensities; a very simple cluster validity criterion is used to determine the optimal number of clusters present in the data. A final step involves a cluster merging procedure driven by edge information provided by a Sobel operator. The algorithm has been tested on SEASAT images.

The peculiarities of digital map images are exploited to develop a watermarking algorithm which is robust against geometric distortions. Robustness against geometric attacks is achieved through text-based image normalization. First, text is extracted from the to-be-marked map, then text orientation and size are exploited to normalize the image geometry prior to watermark insertion. Watermarking is performed by means of any of the existing algorithms ensuring good robustness against image processing tools. At the decoder side, text is extracted again from the map and used to normalize image geometry. Owing to the robustness of text features with respect to common image manipulations, and to the likely spreading of text all across the digital map, the proposed system exhibits an excellent robustness, as is witnessed by the experimental results reported.

This paper deals with robust watermarking of cartographic images. We present a method (text-based geometric normalization-TBGN) which, by exploiting the particular content of cartographic images, namely text content, permits one to cope with global geometric transformations. The validity of the method is validated by experimental results.

Progress in electronic imaging over the last years has encouraged the development of new tools for cultural heritage applications. In particular, the areas of painting preservation and restoration have attracted the interest of researchers working in the field of image processing. A virtual tool for painting restoration, which simulates the actual restoration carried out in the restoration laboratory, is presented; in particular, the proposed techniques allow the virtual recovery and filling of the areas of a painting which are damaged by lacunas.

This paper studies the applicability of watermarking techniques to remote sensing imagery. An overview of watermarking is given, and the requirements, imposed by the remote sensing scenario on watermarking techniques, are discussed. As an example, the effect of watermarking on image classification is analyzed.

A new multichannel filter, the vector Huber filter (VHF) is proposed which, by relying on multivariate estimation theory permits to simultaneously remove impulsive and Gaussian noise from color images, while preserving edges and other fine image details. The new filter is obtained by extending the classical gray-scale Huber filter to the multichannel case. By relying on robust estimation theory, the rationale behind the development of the new filter is discussed. An approximated version of the vector Huber filter (the A-VHF filter), is also introduced to reduce the computational burden and making filtering practical. The validity of the A-VHF filter is confirmed by the preliminary experimental results shown in the paper.

Digital watermarking has been revealed to be an efficient technique to cope with the problem of intellectual property rights (IPR) protection of multimedia data. This technology embeds into the data an unperceivable digital code, namely the watermark, carrying information about the copyright status of the work to be protected. In this paper, the practical feasibility of IPR protection of multimedia data through digital watermarking is investigated. As it is shown, the effectiveness of watermarking as an IPR protection tool turns out to be heavily affected by the detection strategy, which has to be carefully matched to the application at hand. Finally the practical case of the Tuscany&Gifu Art Virtual Gallery has been considered in detail, to further explain in which manner a watermarking technique can be actually used.

Earth observation missions have recently attracted a growing interest, mainly due to the large number of possible applications capable of exploiting remotely sensed data and images. Along with the increase of market potential, the need arises for the protection of the image products. Such a need is a very crucial one, because the Internet and other public/private networks have become preferred means of data exchange. A critical issue arising when dealing with digital image distribution is copyright protection. Such a problem has been largely addressed by resorting to watermarking technology. A question that obviously arises is whether the requirements imposed by remote sensing imagery are compatible with existing watermarking techniques. On the basis of these motivations, the contribution of this work is twofold: assessment of the requirements imposed by remote sensing applications on watermark- based copyright protection, and modification of two well-established digital watermarking techniques to meet such constraints. More specifically, the concept of near-lossless watermarking is introduced and two possible algorithms matching such a requirement are presented. Experimental results are shown to measure the impact of watermark introduction on a typical remote sensing application, i.e., unsupervised image classification.

In the field of image watermarking, research has been mainly focused on gray scale image watermarking; the extension to the color case still represents one of the open issues watermarking researchers are faced with. To solve the problem of the correlation among image color bands, a new approach is proposed here which is based on the exploitation of the de-correlation property of the Karhunen-Loeve transform (KLT). The KLT is applied to the red, green, blue components of the host image, then watermarking is performed independently in the discrete Fourier transform (DFT) do- main of the KL-transformed bands. In order to preserve watermark invisibility, embedding is achieved by modifying the magnitude of mid-frequency DFT coefficients according to an additive- multiplicative rule. In detection, KL de-correlation is exploited to de- sign an optimum watermark decoder. In particular, based on the Neyman-Pearson criterion, the watermark presence is revealed by comparing a likelihood function against a threshold. Experimental results are presented proving the robustness of the algorithm against the most common image manipulations, and its superior performance with respect to techniques based on luminance watermarking. © 2002 SPIE and IS&T. (DOI: 10.1117/1.1426383)

The specification and the management of Quality of Service (QoS) are important aspects in mobile telecommunication networks. There are increasing interests and open issues in providing users with a wide range of multimedia services, in particular for video-telephony applications in a third generation cellular system environment. This paper presents a performance assessment of combined voice-video transmission in a realistic UMTS scenario in which the radio interface is simulated by using the environment offered by OPNET ( Optimized Network Engineering Tool ). In such a context, it is possible to take into account the effects of interference and mobility in a classical cellular scenario. Hence, we can evaluate the effectiveness of different solutions: power control and macro-diversity at the physical layer, coding and retransmission strategies at the link layer and handover, resource allocation and scheduling schemes at the network layer. Power control is designed in order to adapt the power transmitted by mobile terminals on the basis of interference level, traffic and channel conditions, and required packet loss probability. Two main aspects are considered to test the system performance: the ability to support given QoS requirements for both voice and video services - by using accurate models for voice sources and real H.263 video sources - and the effectiveness in the utilization of system resources. Toward this end, simulations are performed for various configurations of parameters and different environmental conditions with a particular attention devoted to the QoS for video transmission.

Earth observation missions have recently attracted ag rowing interest form the scientific and industrial communities, mainly due to the large number of possible applications capable to exploit remotely sensed data and images. Along with the increase of market potential, the need arises for the protection of the image products from non-authorized use. Such a need is a very crucial one even because the Internet and other public/private networks have become preferred means of data exchange. A crucial issue arising when dealing with digital image distribution is copyright protection. Such a problem has been largely addressed by resorting to watermarking technology. A question that obviously arises is whether the requirements imposed by remote sensing imagery are compatible with existing watermarking techniques. On the basis of these motivations, the contribution of this work is twofold: i) assessment of the requirements imposed by the characteristics of remotely sensed images on watermark-based copyright protection ii) analysis of the state-of-the-art, and performance evaluation of existing algorithms in terms of the requirements at the previous point.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

This paper has a threefold goal. First an error resilience technique based on UEP-FEC, proposed by the authors in a previous work, is extended to incorporate a more efficient, adaptive, intra refresh mechanism based on an error-sensitivity metric representing the vulnerability of each coded block to channel errors. Second, the validity of the UEP technique for video transmission over a WCDMA channel is evaluated, thus extending the range of applicability of the above technique, which was originally conceived for and validated on DECT, slow fading, channels. Third, by elaborating on experimental evidence, we prove again that a final judgement on which is the best performing resilience strategy can not be given, without taking into account channel conditions, especially the Doppler spread value.

So far, only a limited attention has been paid to the distinction between readable and detectable watermarking. A drawback with detectable watermarking is that the embedded code can convey only 1 bit of information. Actually, if one could look for all possible watermarks, then the detection of one such watermark would convey log2N information bits. Unfortunately, such an approach is not computationally feasible, since the number of possible watermarks is usually very high. In this work we explore two alternative strategies to build a readable watermark by starting from a detectable one. According to the first strategy (position encoding), information bits are encoded in the position of M known pseudo-random sequences, embedded within the host document by relying on a generic detectable watermarking algorithm. In the second case (amplitude encoding), the pseudo-random sequence is split into a set of sub-sequences, and each sub-sequence is modulated by multiplying it by +1 or -1. To compare the two different approaches, we focus on image watermarking achieved through a well-known, frequency-domain watermarking algorithm previously proposed by the authors. The two alternative strategies are compared both from the point of view of bit error probability and watermark presence assessment.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Low-level, or pixel-based, fusion tends to use efficiently the information data acquired by sensors having different spatial and radiometric resolutions. Several methods have been proposed for merging panchromatic and multispectral data. Recently, multiresolution analysis has become one of the most promising methods for the analysis of remote sensing images. The use of the wavelet “a trous” algorithm allows to apply a dyadic wavelet to merge nondyadic data, by using a stationary or redundant transform, for which decimation is not carried out. The high-resolution coefficients of the image having high spatial resolution, may be added to the luminance component of the multispectral data. This procedure, namely AWL, which starts from a redundant bandpass representation of the image data, is very appealing, because the spectral quality is obviously highly preserved. However, it may suffer from a non-uniform spatial enhancement of the multispectral bands. In this paper, a method is proposed which uses spatial local information on the wavelet planes obtained from the “a trous” wavelet decomposition. The paper aims to improve the additive method by incorporating contextual spatial information to reduce possible overenhancement of the multispectral data in the image regions having higher spectral content, e.g., in highly textured regions.

The demand for remote sensing data has increased dramatically mainly due to the large number of possible applications capable to exploit remotely sensed data and images. As in many other fields, along with the increase of market potential and product diffusion, the need arises for some sort of protection of the image products from unauthorized use. Such a need is a very crucial one even because the Internet and other public/private networks have become preferred and effective means of data exchange. An important issue arising when dealing with digital image distribution is copyright protection. Such a problem has been largely addressed by resorting to watermarking technology. Before applying watermarking techniques developed for multimedia applications to remote sensing applications, it is important that the requirements imposed by remote sensing imagery are carefully analyzed to investigate whether they are compatible with existing watermarking techniques. On the basis of these motivations, the contribution of this work is twofold: (1) assessment of the requirements imposed by the characteristics of remotely sensed images on watermark-based copyright protection; (2) discussion of a case study where the performance of two popular, state-of-the-art watermarking techniques are evaluated by the light of the requirements at the previous point.

The extension of gray level watermarking to the color case is one of the open issues watermarking researchers are still facing with. To get rid of the correlation among image color bands, a new approach is proposed in this paper which is based on the decorrelation property of the Karhunen-Loeve Transform (KLT). First, the KLT is applied to the RGB components of the host image, then watermarking is performed independently in the DFT domain of the KL-transformed bands. In order to preserve watermark invisibility, embedding is achieved by modifying the magnitude of mid-frequency DFT coefficients according to an additive-multiplicative rule. Different weights are used for the three KL bands to further enhance invisibility. On the decoder side, KL decorrelation is exploited to optimally detect the watermark presence. More specifically, by relying on Bayes statistical decision theory, the probability of missing the watermark is minimized subject to a fixed false detection rate. Basing on the Neymann-Pearson criterion, the watermark presence is revealed by comparing a likelihood function against a threshold, if the former is above the latter the decoder decides for the watermark presence, otherwise such an hypothesis is rejected. Experimental results are shown proving the robustness of the algorithm against the most common image manipulations, and its superior performance with respect to conventional techniques based on luminance watermarking.

The objective of this work is to analyze and compare H.263 resilience techniques for H.223-based real-time video transmission over narrow-band slow-fading channels. These channel conditions, which are typical for pedestrian video communications, are very critical, because they require Forward Error Correction (FEC), since data retransmission is not feasible, due to high network delay, and they reduce the effectiveness of FEC techniques- due to the bursty nature of the channel. In this work, two different strategies for H.263 video protection against channel errors are considered and compared. The strategies are tested over a slow-fading wireless channel, over which the H.263 video streams, organized and multiplexed by the H.223 Multiplex Protocol, are transmitted. Both standard FEC techniques considered by the H.223 recommendation for equal error protection of the video stream, and unequal error protection (UEP) through GOB synchronization are tested. The experimental results of this comparative analysis prove the superiority of the UEP technique for H.223-based video transmission.

In this work we evaluate the effectiveness of syntax-based error detection in the context of H.263 video transmission over a noisy, error-prone, channel. We assume transmission is carried out over a non-protected channel, i.e., no information about error occurrence is fed to the application by the transport layer. More specifically, the probability of missing an error or revealing one when no error is actually present is calculated. Particular care is taken to distinguish between macroblock (MB) data errors and header errors, since they have a different impact on reconstructed video quality. We also investigate the possibility of interpreting errors by relying on syntax information only: e.g. we try to discriminate between errors affecting motion vectors and errors altering the value of DCT coefficients. Extensive testing, performed at different rates and with channels characterized by different error probabilities, suggests that the necessity exists of using more reliable error detection approaches.

A problem often raised by the availability of increasingly powerful signal processing tools is the lost of credibility of digital images and video sequences, due to the ease of modifying their content without leaving any visible traces of the modification. Such a problem assumes an outstanding importance in Advanced Video-based Surveillance (AVS) applications, where video sequences virtually have no value as proofs in front of a court of law, since doubts would always exist about the possibility that they had been tampered to intentionally incriminate or exculpate the defendant.