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In this paper we present a method to localize a cylindral surface with only one perspective view. Based on a priori knowledge we find two axes in the image in order to obtain the three rotation angles between the cylindrical surface coordinate system and the camera coordinate system. Various applications of the proposed method are presented.

International audience; In an industrial context, most manufactured objects are designed using CAD (Computer-Aided Design) software. For visualization, data exchange or manufacturing applications, the geometric model has to be discretized into a 3D mesh composed of a finite number of vertices and edges. However, the initial model may sometimes be lost or unavailable. In other cases, the 3D discrete representation may be modified, e.g. after numerical simulation, and no longer corresponds to the initial model. A retro-engineering method is then required to reconstruct a 3D continuous representation from the discrete one. In this paper, we present an automatic and comprehensive retro-engineering process dedicated mainly to 3D meshes obtained initially by mechanical object discretization. First, several improvements in automatic detection of geometric primitives from a 3D mesh are presented. Then a new formalism is introduced to define the topology of the object and compute the intersections between primitives. The proposed method is validated on 3D industrial meshes.

International audience; Efficient data synchronization for 3D mesh models is a new major challenge. 3D models are also now being used to an increasing extent and with current network technology, 3D model compression, visualization and protection demand increases. However, there is still no perfect method to achieve this data synchronization while being blind and robust against variousattacks. We propose a blind method based on a Hamiltonian path to synchronize vertex clouds, and particularly on 3D meshes. We experimentally show that it is fast and robust against Gaussian noise. This novel approach can generate better results than meshbased methods because it does not use vertex connectivity.

Part 2: Work in Progress; International audience; An invisible flow watermarking QIM scheme based on linear error-correcting subcodes for channels with substitution and deletion errors is proposed in this paper. The evaluation of scheme demonstrates similar to known scheme performance but with lower complexity as soon as its implementation is mainly based on linear decoding operations.

International audience; Nowadays, there is an increasing number of digital comics, so-called e-comics, available on Internet. Protecting these ecomics without Digital Rights Management (DRM) is a new issue. In this paper, we propose a method to ensure the protection of e-comics by encrypting only bubbles so that the story will not be understandable. To develop this method, we used standards like JPEG compression and AES encryption. The first step of the method involves detecting bubbles, and we decided to use the MSER algorithm, which is the most commonly used for text detection. The second main step involves making these areas unreadable by encrypting AC coefficients of the JPEG block, corresponding to high frequencies during entropy coding. Several experimental results show the efficiency of the proposed method.

International audience; In the field of video protection, selective encryption (SE) is a scheme which ensures the visual security of a video by encrypting only a small part of the data. This paper presents a new SE algorithm for H.264/AVC videos in CAVLC mode. This algorithm controls the amount of encrypted alternative coefficients (AC) of the integer transform in the entropic encoder. The structural similarity (SSIM) is used to measure the visual confidentiality level of each video frame and to control the amount of encrypted AC. Moreover, a new psychovisual metric to measure the flickering is introduced, the so-called TSSIM. This method can be applied on intra and inter frame video sequences. Several experimental results show the efficiency of the proposed method.

International audience; HUGO [1] and MOD [2] are the most secure adaptive embedding algorithms of 2011. These algorithms strive to hide a secret message, while minimizing an ad hoc embedding impact. They use a detectability map, which, if properly defined, is correlated to the security. In this paper, we present a new adaptive embedding scheme: Adaptive Steganography by Oracle (ASO). It is based on an oracle used to calculate the detectability map, and this oracle use the Kodovsky's ensemble classifiers [3]. Our approach preserves both cover image and sender's database distributions during the embedding process, which improves the security. In addition, it offers to the sender the opportunity to choose the most reliable image(s), during his secret communication. Experimental results show that our embedding scheme presents good secu-rity performances, since the detection error of ASO is much higher than that of HUGO.

International audience; With the ever-increasing development of digital technologies and digital 3D models, the question of 3D mesh protection has becoming more and more important. One of the problems in digital watermarking is to decide how to embed in a 3D mesh as many bits of information as possible while ensuring that the hidden information can be correctly retrieved after 3D mesh compression. This paper describes a hybrid watermarking/compression system, adapted to semi-regular 3D meshes. The central contribution is to integrate blind watermarking, to geometric progressive compression algorithm. The latter consists on semi-regular wavelet transform and zerotree coding approach. The proposed embedding method operates in the discrete wavelet transform domain using dither modulation principal. This work shows the ability of joint watermarking/compression scheme to guarantee watermark robustness against compression attacks while inducing a low quality degradation.

International audience; Abstract In this paper, we present a novel approach for active fingerprinting of state of the art video codec H.264/AVC. Tardos probabilistic ngerprinting code is embedded in H.264/AVC video signals using spread spectrum watermarking technique in both luma and chroma. Tardos code is embedded in intra as well as inter frames. The embedding has been performed in the non-zero quantized transformed coe cients (QTCs), which are above a certain threshold while taking into account the reconstruction loop, to avoid the uncontrollable increase in bitrate of video bitstream. A comprehensive analysis of payload and PSNR trade-o ff is presented for benchmark video sequences. Di erent linear and non-linear collusion attacks have been performed in the pixel domain to show the robustness of the proposed approach.

International audience; This paper deals with a method to protect the color information of images by providing free access to the corresponding gray level images. Only with a secret key and the gray level images, it is then possible to view the images in color. The approach is based on a color reordering algorithm after a quantization step. Based on a layer scanning algorithm, the color reordering generates gray level images and makes it possible to embed the color palette into the gray level images using a data hiding algorithm. This work was carried out in the framework of a project aimed at providing limited access to the private digital painting database of the Louvre Museum in Paris, France.

International audience; This paper presents a novel method for the real-time protection of new emerging High Efficiency Video Coding (HEVC) standard. Structure preserving selective encryption is being performed in CABAC entropy coding module of HEVC, which is significantly different from CABAC entropy coding of H.264/AVC. In CABAC of HEVC, exponential Golomb coding is replaced by truncated Rice (TR) up to a specific value for binarization of transform coefficients. Selective encryption is performed using AES cipher in cipher feedback mode on a plaintext of binstrings in a context aware manner. The encrypted bitstream has exactly the same bit-rate and is format complaint. Experimental evaluation and security analysis of the proposed algorithm is performed on several benchmark video sequences containing different combinations of motion, texture and objects.

International audience; This paper presents an efficient method for high payload reversible data-hiding in H. 264/AVC intra bitstream with a minimal drift, which is controllable and proportional to the payload. In contrast to previously presented open-loop reversible data hiding techniques for H. 264/AVC bitstream, which mainly perform drift-compensation, we propose a new reversible data hiding technique for H. 264/AVC intra bitstream which avoids drift. The major design goals of this novel H.264/AVC reversible data hiding algorithm have been runtime-efficiency, high perceptual quality with a minimal effect on bit-rate. The data is efficiently embedded in the compressed domain in an open-loop fashion, i.e., all prediction results are reused. Nevertheless intra-drift is avoided, as only specific solution patterns are added, which are solutions of a system of linear equations that guarantee the preservation of the block's edge pixel values.

Building energy consumption is an important problem in construction field, old buildings are gap of energy and they need to be refactored. Energy footprint of buildings needs to be reduced. New buildings are designed to be suitable with energy efficiency paradigm. To improve energy efficiency, Building Management Systems (BMS) are used: BMS are IT (Information Technology) systems composed by a rules engine and a database connected to sensors. Unfortunately, BMS are only monitoring systems: they cannot predict and mine efficiently building information. RIDER project has emerged from this observation. This project is conducted by several French companies and universities, IBM at Montpellier, France, leads the project. The main goal of this project is to create a smart and scalable BMS. This new kind of BMS will be able to dig into data and predict events. This IT system is based on component paradigm and the core can be extended with external components. Some of them are developed during the project: data mining, building generation model and visualization. All of these components will provide new features to improve rules used by the core. In this paper, we will focus on the visualization component. This visualization use a volume rendering method based on sensors data interpolation and a correlation method to create new views. We will present the visualization method used and which rules can be provided by this component.

International audience; Joint Entropy Coding and Encryption in AVS Video Codec

In this paper, we propose a system for the automated classification of liver focal lesions of Computer Tomography (CT) images based on a multi-phase examination protocol. Many visual features are first extracted from the CT-scans and then labelled by a Support Vector Machine classifier. Our dataset contains 95 lesions from 5 types: cysts, adenomas, haemangiomas, hepatocellular carcinomas and metastasis. A Leave-One-Out cross-validation technique allows for classification evaluation. The multi-phase results are compared to the single-phase ones and show a significant improvement, in particular on hypervascular lesions.

National audience; Dans cet article, nous proposons d'utiliser la représentation de distributions de valeurs par histogrammes quasi-continus pour réaliser une détection temps réel de mouvement dans une séquence d'images. Nous comparons les résultats de cette détection à deux méthodes de référence de la littérature.

International audience; In the field of video protection, selective encryption (SE) is a scheme which ensures a visual security of video by encrypting a small part of data. This paper presents a new SE algorithm for H.264/AVC in CAVLC mode. This algorithm controls the amount of encrypted alternative coefficients (AC) of the integer transform in the entropic encoder. Two visual quality measures, the peak signal-to-noise ratio (PSNR) and the structural similarity (SSIM), are used to measure the visual confidentiality level of each video frame and to regulate the amount of encrypted alternatives coefficients. This method can be applied on intra and inter frame video sequences.

In this paper, a new no-reference image quality metric is proposed to estimate the quality of watermarked images automatically based on combining objective metrics using neural network. The aim is to predict the subjective quality scores, known as the mean opinion score (MOS) obtained from human observers. In practice, our metric consists of three stages: first, filtering process is applied to watermarked image in order to generate its filtered image. Second, we use watermarked image and its filtered image in the calculation of the objective metrics as input to a neural network. Third; these metrics are combined using neural network model. The output of this neural network is a single value corresponding to the MOS scores. Experimental results show that combination of objective metrics through the neural network, indeed is able to accurately predict perceived quality of watermarked images.

International audience; ASO [1] is an adaptive embedding scheme that has proved its efficiency compared to HUGO [2] algorithm. It is based on the use of a detectability map that is correlated to the security of the embedding process. The detectability map is calculated using the Kodovsky's ensemble classifiers [3] as an oracle, which preserves the distribution of the cover image and of the sender's database. In this article, we give the technical points about ASO. We give the details of the detectability map computation, then we study the security of the communication phase of ASO through the paradigm of the steganography by database. Since the introduced paradigm allows the sender to choose the most secure stego image(s) during the transmission of his message, we propose some security metrics that can help him to distinguish between secure and insecure images. We thus significantly increase the security of ASO.

International audience; We present a novel scheme for high-capacity of 3-D triangle meshes. Our proposal can be applied to meshes with arbi- trary topology by using irregular wavelet-based analysis. The secret message is inserted in an appropriate resolution level by quantizing the norms of wavelet coefficients vectors. In addition, a re-ordering process is applied as pre-processing in both embedding and extraction stages. Simulation results show that our data hiding framework is robust to common geometric attacks including the operations of the similarity transformations and achieves high data capacity with insignif- icant visual distortion.

This chapter presents methods for the protection of privacy associated with specific regions from colour images or colour image sequences. In the proposed approaches, regions of interest (ROI) are detected during the JPEG compression of the colour images and encrypted. The methodology presented in this book chapter performs simultaneously selective encryption (SE) and image compression. The SE is performed in a ROI and by using the Advanced Encryption Standard (AES) algorithm. The AES algorithm is used with the Cipher Feedback (CFB) mode and applied on a subset of the Huffman coefficients corresponding to the AC frequencies chosen according to the level of required security. In this study, we consider the encryption of colour images and image sequences compressed by JPEG and of image sequences compressed by motion JPEG. Our approach is performed without affecting the compression rate and by keeping the JPEG bitstream compliance. In the proposed method, the SE is performed in the Huffman coding stage of the JPEG algorithm without affecting the size of the compressed image. The most significant characteristic of the proposed method is the utilization of a single procedure to simultaneously perform the compression and the selective encryption rather than using two separate procedures. Our approach reduces the required computational complexity. We provide an experimental evaluation of the proposed method when applied on still colour images as well as on sequences of JPEG compressed images acquired with surveillance video cameras.

With the fast advancement of computer, multimedia and network technologies, the amount of multimedia information that is conveyed, broadcast or browsed via digital devices has grown exponentially. Simultaneously, digital forgery and unauthorized use have reached a significant level that makes multimedia authentication and security very challenging and demanding. The ability to detect changes in multimedia data has been very important for many applications, especially for journalistic photography, medical or artwork image databases. This has spurred interest in developing more robust algorithms and techniques to allow to check safety of exchanged multimedia data confidentiality, authenticity and integrity. Confidentiality means that the exchange between encrypted multimedia data entities, which without decryption key, is unintelligible. Confidentiality is achieved mainly through encryption schemes, either secret key or public key. Authentication is an another crucial issue of multimedia data protection, it makes possible to trace the author of the multimedia data and allow to determine if an original multimedia data content was altered in any way from the time of its recording. Integrity allows degradation detection of multimedia and helps make sure that the received multimedia data has not been modified by a third party for malicious reasons. Many attempts have been noted to secure multimedia data from illegal use by different techniques fields such as encryption field, watermarking field and perceptual image hashing field. The field of encryption is becoming very important in the present era in which information security is of the utmost concern to provide end-to-end security. Multimedia data encryption has applications in internet communication, multimedia systems, medical imaging, telemedicine, military communication, etc. Although we may use the traditional cryptosystems to encrypt multimedia data directly, it is not a good idea for two reasons. The first reason is that the multimedia data size is almost always much great. Therefore, the traditional cryptosystems need much more time to directly encrypt the multimedia data. The other problem is that the decrypted multimedia data must be equal to the original multimedia data. However, this requirement is not necessary for image/video data. Due to the characteristic of human perception, a decryptedmultimedia containing small distortion is usually acceptable. Deciding upon what level of security is needed is harder than it looks. To identify an optimal security level, the cost of the multimedia information to be protected and the cost of the protection itself are to be compared carefully. At present, many available image encryption algorithms have been proposed (Ozturk & Ibrahim, 2005; 2

Recently, a variety of chaos-based cryptosystems have been proposed. Some of these novel chaotic encryption schemes are not very suitable for image encryption because of their density function which is not uniformly distributed or because of their small key space. Note that for some chaotic map, their control parameters and initial values can be found easily. In this paper, we propose a new scheme for image encryption based on the use of the standard chaotic map with large key space and Engle Continued Fractions (ECF) map. The ECF-map is employed to generate a pseudo random sequence which satisfies uniform distribution, zero co-correlation and ideal nonlinearity to achieve higher level of security. The proposed scheme is resistant to statistic attacks, differential attacks and some other known attacks. Theoretic and numerical simulation analyses on 100 images indicate that our scheme is efficient and satisfies high security.

This paper presents a traitor tracing method dedicated to video content distribution. It is based on a two-level approach with probabilistic traitor tracing codes. Codes are concatenated and decoded successively, the first one is used to decrease the decoding complexity and the second to accuse users. We use the well-known Tardos fingerprinting code for the accusation process and a Boneh-Shaw code with replication scheme to reduce the search space of users. This method ensures a decrease of the computational time compared to classical Tardos codes decoding. We present a method to select suspect groups of users and compare it to a more complex two-level Tardos code which follows the same construction.

Nowadays, most of the manufactured objects are designed using CAD (Computer-Aided Design) software. Nevertheless, for visualization, data exchange or manufacturing applications, the geometric model has to be discretized into a 3D mesh composed of a finite number of vertices and edges. But, in some cases, the initial model may be lost or unavailable. In other cases, the 3D discrete representation may be modified, for example after a numerical simulation, and does not correspond anymore to the initial model. A reverse engineering method is then required to reconstruct a 3D continuous representation from the discrete one. In previous work, we have presented a new approach for 3D geometric primitive extraction. In this paper, to complete our automatic and comprehensive reverse engineering process, we propose a method to construct the topology of the retrieved object. To reconstruct a B-Rep model, a new formalism is now introduced to define the adjacency relations. Then a new process is used to construct the boundaries of the object. The whole process is tested on 3D industrial meshes and bring a solution to recover B-Rep models.

Multimedia protection is one of the main research challenges in computer sciences. We can encrypt the media in order to make the content unreadable without a secret key of decryption, protect the file with Digital Right Management (DRM), or embed an hidden message in the file (watermarking and steganography). We are interested in data hiding applications for 3D mesh. In this domain, there are various problems, of which the synchronization of the message in the support host. The synchronization is the operation that allows to scan a mesh with a unique path and by selecting the same areas (vertices, triangles, quadrangles, for example) before and after the embedding even if the mesh has been noised. In this paper, we propose a new synchronization approach based on feature point selection in a low resolution of the 3D object. The building of the low resolution is made by decimation and the feature point selection is based on the discrete curvature computing. We evaluate the robustness of the synchronization in the low resolution and in the high resolution.

International audience; Robots have primarily been developed for warfare, yet they also serve peaceful purposes. Their use in Ecology is in its infancy, but they may soon become essential tools in a broad variety of eco-logical sub-disciplines. Autonomous robots, in particular drones sent to previously inaccessi-ble areas, have revolutionized data acquisition, not only for abiotic parameters, but also for re-cording the behavior of undisturbed animals and collecting biological material. Robots will also play an essential role in population Ecology, as they will allow for automatic census of indi-viduals through image processing, or via detec-tion of animals marked electronically. These new technologies will enable automated experimen-tation for increasingly large sample sizes, both in the laboratory and in the field. Finally, inter-active robots and cyborgs are becoming major players in modern studies of animal behavior. Such rapid progress nonetheless raises ethical, environmental, and security issues.

International audience; In this chapter, we present a project called RIDER, for Research for IT Driver EneRgy efficiencies. We are developing a green box composed by a set of IT components; able to generate efficient predictive model and building optimization. The main part of the green box is a pivot model managed by a rule engine and a standard BMS with a specific input/output protocol. Modules can extend the standard green box offering system/user advices, proposing improvements on data model and predicting building behavior. This chapter introduces the RIDER green box and details the visualization module, which is used to improve model by using user knowledge.

International audience; In this paper, a novel method for independent access of di ff erent layers of protected scalable video coding (SVC), based on framework of state of the art H.264 / AVC, is presented. For a SVC bitstream, a user accessing the base layer needS only one key while users accessing the enhancement layer need keys for both the base layer and enhancement layer. Hence if a user is accessing the highest available layer, keys of all the lower layers are also needed to decode it properly. We have devised a scheme in which the user accessing any particular resolution use only one key whether it is the base layer or any of the enhancement layers, and all the keys have the same length. Advanced encryption standard (AES) algorithm in Cipher Feedback (CFB) mode has been used in this scheme to make the keys secure. The scheme has been tested both for o ffl ine playback and online streaming environment. Five di ff erent benchmark video sequences having three resolutions and containing di ff erent combinations of motion, texture and objects are used for experimental evaluation of the proposed algorithm.

In this paper, we propose new watermarking method for image copyright protection in spatial domain based on fuzzy image segmentation technique. The fuzzy image approach is employed to determine appropriate locations to hiding watermark by identifying the features map (edges regions) which are less sensitive to the human visual system. Our method optimizes robustness and imperceptibility which are known to be inversely proportional to each other. Transparency performance of proposed method was evaluated by four image quality measures are PSNR, SSIM and two similarity measures which are based on the fuzzy logic S 1 , S 2 . The evaluation results demonstrate the high robustness of the proposed algorithm against the common image processing operators. Our method is also is efficient as it only uses simple operations such image fuzzification and fuzzy image segmentation technique.

In this paper we present a new approach of selective encryption (SE) of video. SE is currently applied to video codec H.264/AVC in order to perform confidentiality and preserve bitrate and data size of the underlying video sequence. Our approach analyzes, each macro-block of a given video sequence, separately before its entropy encoding. In this way, the system decides whether it is necessary to or not to encrypt the current macro-block. On the former case, the selected macro-block is encrypted using the SE-CAVLC in the entropy encoder. This approach allows to encrypt a smaller part of the macro-blocks without disturbing the level of confidentiality.

In this paper, a novel data hiding strategy is proposed to integrate disparity data, needed for 3D visualization based on depth image based rendering, into a single H.264 format video bitstream. The proposed method has the potential of being imperceptible and efficient in terms of rate distortion trade-off. Depth information has been embedded in some of quantized transformed coefficients (QTCs) while taking into account the reconstruction loop. This provides us with a high payload for embedding of depth information in the texture data, with a negligible decrease in PSNR. To maintain synchronization, the embedding is carried out while taking into account the correspondence of video frames. Three different benchmark video sequences containing different combinations of motion, texture and objects are used for experimental evaluation of the proposed algorithm.

National audience; Dans cet article, nous présentons une méthode conjointe de quantification et de dissimulation de données basée sur la Quantification Codée par Treillis (TCQ) dans JPEG2000. La contribution principale de ce travail est que le schéma proposé permet de réaliser conjointement les opérations de quantification et d'insertion des données cachées. Les propriétés de la TCQ sont exploitées afin de quantifier certains coefficients d'ondelettes à l'aide de quantificateurs spécifiques. Ces quantificateurs sont associés aux données à cacher. Les coefficients inclus dans le processus de dissimulation de données sont sélectionnés de manière à ce qu'ils puissent survivre à la phase de contrôle de taux de JPEG2000. Des résultats expérimentaux sont présentés et permettent de conclure que l'insertion des données cachées aboutit à une dégradation minimale des performances de JPEG2000. La charge utile ou payload est importante et dépend du taux de compression cible

International audience; In this paper, we present a new approach for sharing images between l players by exploiting the additive and multiplicative homomorphic properties of two well-known public key cryptosystems, i.e. RSA and Paillier. Contrary to the traditional schemes, the proposed approach employs secret sharing in a way that limits the in fl uence of the dealer over the protocol and allows each player to participate with the help of his key-image. With the proposed approach, during the encryption step, each player encrypts his own key-image using the dealer's public key. The dealer encrypts the secret-to-be-shared image with the same public key and then, the l encrypted key-images plus the encrypted to-be shared image are multiplied homomorphically to get another encrypted image. After this step, the dealer can safely get a scrambled image which corresponds to the addition or multiplication of the l +1 original images ( l key-images plus the secret image) because of the additive homomorphic property of the Paillier algorithm or multiplicative homomorphic property of the RSA algorithm. When the l players want to extract the secret image, they do not need to use keys and the dealer has no role. Indeed, with our approach, to extract the secret image, the l players need only to subtract their own key-image with no speci fi c order from the scrambled image. Thus, the proposed approach provides an opportunity to use operators like multiplication on encrypted images for the development of a secure privacy preserving protocol in the image domain. We show that it is still possible to extract a visible version of the secret image with only l -1 key-images (when one key-image is missing) or when the l key-images used for the extraction are different from the l original key-images due to a lossy compression for example. Experimental results and security analysis verify and prove that the proposed approach is secure from cryptographic viewpoint.

In this paper, we consider the problem of the quantization stage of robust perceptual image hashing in authentication application. The main goal of our analysis is to study the behavior of the extracted image features to be hashed against malicious/non-malicious manipulations. In our analysis, we consider only an additive noise. Note that even if the noise is small, it can cause errors during the quantization stage of perceptual image hashing system. For this purpose, we present theoretical analysis of the extracted feature under additive noise, as well as the probability of a false quantization of these selected features. We then introduce our proposed approach based on this theoretical analysis. Finally, several experiments are conducted to validate our theoretical analysis.

Cryptographic techniques are used to secure confidential data from unauthorized access, but these techniques are very sensitive to noise. A single bit change in encrypted data may have catastrophic impact over the decrypted data. This paper addresses the problem of removing bit error in visual data which are encrypted using AES algorithm by block. In order to remove the noise, three statistical analyses are proposed which are based on Global variance, Mean local variance and Sum of squared derivative. These methods exploit local statistics of the visual data and confusion/diffusion properties of the encryption algorithm to correct the errors. Experimental results show that the proposed approaches can be used at the receiving end for the possible solution for error correction in visual data in encrypted domain.

This paper presents a contribution in matter of robustness of a previous method of 3D objects watermarking [10] based on wavelet decomposition on semi-regular triangular meshes. This decomposition gives rise to a multiresolution mesh where the watermark could be embedded at each level of resolution, in this case we talk about a hierarchical watermarking. In practice the robustness of the previous method against geometrical attacks was high only in the low resolution which makes it far from being a hierarchical method. Our analysis made on the fragility of that method allowed us to reveal the cause which was not primarily the bad bits quantization of the watermark, but rather the alteration of the sequencing of the embedded bits (synchronization). Our contribution is to replace the previous geometrical mechanism with a new topological synchronization mechanism, which has resulted a real hierarchical and robust watermarking.

International audience; This paper presents a novel method for the protection of bitstreams of state-of-the-art video codec H.264/AVC. The problem of selective encryption (SE) is addressed along with the compression in the entropy coding modules. H.264/AVC supports two types of entropy coding modules. Context-adaptive variable length coding (CAVLC) is supported in H.264/AVC baseline profile and context-adaptive binary arithmetic coding (CABAC) is supported in H.264/AVC main profile. SE is performed in both types of entropy coding modules of this video codec. For this purpose, in this paper the encryption step is done simultaneously with the entropy coding CAVLC or CABAC. SE is performed by using the advanced encryption standard (AES) algorithm with the cipher feedback mode on a subset of codewords/binstrings. For CAVLC, SE is performed on equal length codewords from a specific variable length coding table. In case of CABAC, it is done on equal length binstrings. In our scheme, entropy coding module serves the purpose of encryption cipher without affecting the coding efficiency of H.264/AVC by keeping exactly the same bitrate, generating completely compliant bitstream and utilizing negligible computational power. Owing to no escalation in bitrate, our encryption algorithm is better suited for real-time multimedia streaming over heterogeneous networks. It is perfect for playback on handheld devices because of negligible increase in processing power. Nine different benchmark video sequences containing different combinations of motion, texture, and objects are used for experimental evaluation of the proposed algorithm.

The point-based representation constitutes a recent useful alternative approach for modeling enormous and large 3D polygonal models which contain usually millions of faces. However, and in order to allow the artists and the designers to work with such representation, a new mechanisms of FFD (Free Form Deformation) must be offered and that especially with an interactive response time or real time response (in the best case). This paper presents an acceleration of FFD for point-based objects and particularly splat-based with interactive response time, and that by exploiting the programmable GPU features of the modern graphics cards.

Multiplicative homomorphic properties of a cryptosystem can be used in various applications requiring security, protection and authentication e.g. digital fingerprinting, electronic voting, on line betting etc. Secret sharing between two or more parties exploiting multiplicative homomorphic property of RSA results into erroneous blocks while extracting the message. The generation of these erroneous blocks limits the capabilities of homomorphic properties of RSA to be used in its full extend. This paper provides three different approaches as solutions to the problem of erroneous blocks in image. These solutions are: mean value approach, shortest distance approach and image preprocessing approach. It has been observed that shortest distance approach results into good PSNR but it is computationally expensive. The best approach with high PSNR is image preprocessing approach before sharing process, which results into no erroneous blocks in the extracted image, thus no extra extraction techniques are required.

International audience; This paper discusses the experimental results of our visualization model for data extracted from sensors. The objective of this paper is to find a computationally efficient method to produce a real time rendering visualization for a large amount of data. We develop visualization method to monitor temperature variance of a data center. Sensors are placed on three layers and do not cover all the room. We use particle paradigm to interpolate data sensors. Particles model the "space" of the room. In this work we use a partition of the particle set, using two mathematical methods: Delaunay triangulation and Vorono ̈ı cells. Avis and Bhattacharya present these two algorithms in1 . Particles provide information on the room temperature at different coordinates over time. To locate and update particles data we define a computational cost function. To solve this function in an efficient way, we use a client server paradigm2 . Server computes data and client display this data on different kind of hardware. This paper is organized as follows. The first part presents related algorithm used to visualize large flow of data. The second part presents different platforms and methods used, which was evaluated in order to determine the better solution for the task proposed. The benchmark use the computational cost of our algorithm that formed based on located particles compared to sensors and on update of particles value. The benchmark was done on a personal computer using CPU, multi core programming, GPU programming and hybrid GPU/CPU. GPU programming method is growing in the research field; this method allows getting a real time rendering instates of a precompute rendering. For improving our results, we compute our algorithm on a High Performance Computing (HPC), this benchmark was used to improve multi-core method. HPC is commonly used in data visualization (astronomy, physic, etc) for improving the rendering and getting real-time.

In an industrial context, recovering a continuous model is necessary to make modifications or to exchange data with a format including continuous representation of objects like STEP. But for many reasons, the initial continuous object can be lost after a display or an exchange with a discretized format. The mesh can also be deformed after a numerical computation. It is then important to have a method to create a new continuous model of the object from a mesh. In case of CAD object, the first step is to detect simple primitives like: plane, sphere, cone and cylinder from a 3D CAD mesh. This paper is focused on this step. This method of detection use curvature features to recover each primitive type. Segmentation is based on the curvature feature computed for each vertex. It permits to extract sub-meshes. Each one corresponds to a primitive. Parameters of these primitives are found with a fitting process according to the curvature features.

Improvement of edge details in an image is basically a process of extracting high frequency details from the image and then adding this information to the blurred image. In this paper we propose an image sharpening technique in which high frequency details are extracted using wavelet transforms and then added with the blurred image to enhance the edge details and visual quality. Before this addition, we perform some spatial domain processing on the high pass images, based on hysteresis, to suppress the pixels which may not belong to the edges but retained in the high-pass image.

International audience; This paper deals with a 3D visualization technique proposed to analyze and manage energy efficiency from a data center. Data are extracted from sensors located in the IBM Green Data Center in Montpellier France. These sensors measure different information such as hygrometry, pressure and temperature. We want to visualize in real-time the large among of data produced by these sensors. A visualization engine has been designed, based on particles system and a client server paradigm. In order to solve performance problems, a Level Of Detail solution has been developed. These methods are based on the earlier work introduced by J. Clark in 1976.1 In this paper we introduce a particle method used for this work and subsequently we explain different simplification methods we have applied to improve our solution.

International audience; In this paper, a novel data hiding strategy is proposed to integrate disparity data, needed for 3D visualization based on depth image based rendering, into a single H.264 format video bitstream. The proposed method has the potential of being imperceptible and efficient in terms of rate distortion trade-off. Depth information has been embedded in some of quantized transformed coefficients (QTCs) while taking into account the reconstruction loop. This provides us with a high payload for embedding of depth information in the texture data, with a negligible decrease in PSNR. To maintain synchronization, the embedding is carried out while taking into account the correspondence of video frames. Three different benchmark video sequences containing different combinations of motion, texture and objects are used for experimental evaluation of the proposed algorithm.

National audience; Dans cet article, nous présentons une méthode permettant de décomposer un maillage triangulaire en un ensemble de carreaux quadrangulés. Elle se base sur la construction de quadrangles par fusion de triangles. Les quadrangles sont ensuite regroupés afin de composer des zones quadrangulées qui sont redécoupées en carreaux. Cette méthode a la particularité de ne pas modifier les points du maillage triangulaire d'origine contrairement à de nombreuses méthodes de remaillage. Les carreaux quadrangulés extraits peuvent ensuite être utilisés comme support d'une surface paramétrique ou d'un schéma de subdivision

International audience; Synchronization in 3D data hiding is one of the main problems. We need to know where we can embed informa- tion, and be able to find this space in order to extract the message. Various algorithms propose synchronization techniques by triangle or vertex path in a 3D mesh. In this paper, we proposed a new synchronization technique based on Euclidean minimum spanning tree computing (EMST) and the analysis of the displacement of the vertices without moving the connections in the tree. Based on the analysis of the vertices, we select the most robust vertices and synchronize these areas by computing a new EMST called "robust EMST". Then, we analyze the robustness of the technique, i.e. the stability of the most robust vertices selection; and demonstrate the consistence of the criterion selection with the vertex displacement.

International audience; In recent years, a variety of chaos-based cryptosystems have been proposed. Some of these systems are used in designing a pseudo random bit generator (PRBG) for stream cipher applications. Most of the chaotic systems used in cryptography have good chaotic properties like ergodicity, sensitivity to initial values and sensitivity to control parameters. However, some of them are not very suitable for use in cryptography because of their non-uniform density function, and their relatively small key space. To be used in cryptography, a PRBG may need to meet stronger requirements than for other applications. In particular, various statistical tests can be applied to the outputs of such generators to conclude whether the generator produces a truly random sequence or not. In this paper, we propose a PRBG based on the use of the standard chaotic map with large key space and the Engle Continued Fractions (ECF) map. The outputs of the standard map are used as the inputs of ECF-map. The chaotic nature of the standard map and the good statistical properties of the ECF map motivate us to design a new PRBG for stream cipher applications. The numerical simulation analysis indicates that our PRBG produces bit sequences possessing excellent statistical and cryptographic properties.