Vassilis Fotopoulos | Hellenic Open University (original) (raw)

Papers by Vassilis Fotopoulos

Abstract:-Digital Signal Processing (DSP) is becoming a core function for organisations that prod... more Abstract:-Digital Signal Processing (DSP) is becoming a core function for organisations that produce, manage and distribute digital content. Promising applications of DSP include coding, rendering, copyright protection, that is highly demanding application in terms of CPU load. In this communication, some specific cases are presented where GRID computing could be used as an enabling/assisting technology for two demanding DSP techniques: watermarking and encoding.

Abstract: Astronomical Image Processing Software (AIPS) is used for radio astronomical data reduc... more Abstract: Astronomical Image Processing Software (AIPS) is used for radio astronomical data reduction of extended radio sources. It saves the output map, together with 'history'of the production of the image into Flexible Image Transport System (FITS) file format. The flux, the noise of the map and any other information is lost, once the image of the radio source is extracted from AIPS. As a consequence, any other discipline astronomer, interested in such information, would have to get familiarized with the radio data reduction.

Abstract–In this work, a new blind watermarking scheme in frequency domain is presented. The prop... more Abstract–In this work, a new blind watermarking scheme in frequency domain is presented. The proposed scheme is based on a chaotic function for embedding, and a correlation method for detection. Three-dimensional maps of PSNR and correlation are used for better selection of embedding parameters according to a quality threshold. The scheme shows increased robustness against JPEG compression and cropping.

Abstract A new spatio-temporal approach is proposed for fast block motion estimation in video cod... more Abstract A new spatio-temporal approach is proposed for fast block motion estimation in video coding. The approach exploits the existing correlation of the spatio-temporal block neighborhood by utilizing the frequency of appearance of the neighborhood's motion vectors. Extensive simulations show that the proposed algorithm performs close to the full search algorithm (in terms of quality) with a significant computational gain. Under fine tuning of specific parameters, the algorithm becomes comparable to other fast search algorithms.

ABSTRACT The wide use of digital media during the past few years, has led to an increase of digit... more ABSTRACT The wide use of digital media during the past few years, has led to an increase of digital piracy and tampering. To deal with these problems, the concept of watermarking has been introduced. The image is being altered and depending on the method used, these alterations can be from very slight to quite noticeable. We propose here a new scheme that identifies image tampering without altering the original image. To achieve that, we extract some unique information from the image that we use for authentication.

Abstract The main purpose of this work is to give a brief overview of video coding, from the main... more Abstract The main purpose of this work is to give a brief overview of video coding, from the main principles to the available standards and future trends, and define augmented reality applications that make use of video. Augmented reality (AR) is a novel scientific field that may benefit by video transmission, however special constraints do apply.

Abstract The transform domain is the most commonly used space for watermarking applications. Most... more Abstract The transform domain is the most commonly used space for watermarking applications. Most of the common frequency transforms have been used for this purpose. We investigate the use of the Gabor (1946) transform in traditional watermarking schemes. A casting method and detection results are thoroughly examined. It seems that traditional detection thresholds are not applicable in this transform, thus a modified approach is employed to overcome this problem. Experimental results are quite encouraging

Abstract In this paper, a new reversible watermarking scheme resistant to geometrical attacks is ... more Abstract In this paper, a new reversible watermarking scheme resistant to geometrical attacks is presented. The proposed scheme does not need the original image for extracting the watermark, and induces not noticeable distortion during the watermarking procedure. The embedding algorithm has low computational complexity, can be applied to very small images (down to 16 x 16), and provides capabilities of multicasting.

Abstract Digital Rights Management (DRM) systems' interoperability is becoming one of the main ob... more Abstract Digital Rights Management (DRM) systems' interoperability is becoming one of the main obstacles for their wider adoption, especially from medium and small size users. Interoperability issues affect, among others, the management of content usage rules by third parties (authorities) and the automation of licensing procedures upon the purchase of digital content. The fundamental question of who is handling content licenses in the national or global DRM value chain is complex, with business, social and technological extensions.

Abstract In this paper a new variation of the well known MAE (Mean Absolute Error) matching crite... more Abstract In this paper a new variation of the well known MAE (Mean Absolute Error) matching criterion for video coding applications, is introduced. The MAE criterion is simpler than the MSE criterion because of the lack of multiplication operations, but it achieves a lower performance in terms of PSNR and MSE. In this work we impose an additional statistical constraint over the MAE thus filling the performance gap between the original MAE and MSE criteria.

ABSTRACT In this paper, a new robust watermarking scheme is presented. The algorithm is based on ... more ABSTRACT In this paper, a new robust watermarking scheme is presented. The algorithm is based on a chaotic function and a correlation method for detection, operating in the frequency domain. The proposed scheme is blind and comparing to other chaos related watermarking methods, experimental results exhibit satisfactory robustness against a wide variety of attacks such as filtering, noise addition, geometric manipulations and JPEG compression with very low quality factors.

Abstract It is now quite common in the pel-recursive approaches for motion estimation, to find ap... more Abstract It is now quite common in the pel-recursive approaches for motion estimation, to find applications of the Kalman filtering technique both in time and frequency domains. In the block-based approach, very few approaches are available of this technique to refine the estimation of motion vectors resulting from fast algorithms such as the three step on a 16× 16-block basis.

Abstract Copyright protection is becoming an important issue for organisations that create, use a... more Abstract Copyright protection is becoming an important issue for organisations that create, use and distribute digital content. One of the most promising methods for copyright protection is digital watermarking, an efficient and robust data hiding technique. In this paper we present the information and system architecture of an intellectual property rights (IPR) protection and management service based on watermarking.

During the last years, the world is rapidly becoming digital in many aspects. Among the most inte... more During the last years, the world is rapidly becoming digital in many aspects. Among the most interesting of these aspects is multimedia. Many new technologies have come into our lives along with multimedia and one of the most recent is watermarking. Digital technology has offered users easy ways to create, process, and distribute digital assets. However, these facilities this may become disadvantages at the same time since it is also much easier to illegally copy and manipulate them.

Abstract Most of the methods involved in transform domain watermarking perform very well in a gre... more Abstract Most of the methods involved in transform domain watermarking perform very well in a great variety of attacks but fail miserably in the category of the attacks known as geometrical. Usually, even a small rotation or slight zoom in/out of the watermarked image, results to detection failure. These attacks can be modelled by means of the affine transform. There are some suggestions that cope with this problem and an overview of them is presented in this communication, along with a new improved solution to this.

Abstract The vast majority of the available watermarking schemes, operate in the frequency domain... more Abstract The vast majority of the available watermarking schemes, operate in the frequency domain. Use of key-dependent transforms has been proposed as an extra level of security for these schemes while providing at the same time the ability to distribute different levels of quality to different customers. The major drawback of such schemes, is the computational complexity, both in the generation of such transforms and making them orthogonal.

Abstract Background: The aim of this study was to determine the genotype distribution and allelic... more Abstract Background: The aim of this study was to determine the genotype distribution and allelic frequencies of ACE (I/D), AGTR1 (A+ 1166 C), BDKRB2 (+ 9/− 9) and LEP (G–2548A) genomic variations in 175 Greek athletes who excelled at a national and/or international level and 169 healthy Greek adults to identify whether some particular combinations of these loci might serve as predictive markers for superior physical condition.

Difference expansion (DE) has been widely used for reversible data hiding. In this paper, a novel... more Difference expansion (DE) has been widely used for reversible data hiding. In this paper, a novel transform which embeds two bits of information in a triplet of coefficients is presented. This transform can be applied in spatial or frequency domains and induces minimum distortion to the initial data or coefficients. The proposed method outperforms all similar DE methods using triplets in terms of computational cost, visual quality and bitrate.

Abstract: Copyright protection is becoming an important issue for organisations that distribute d... more Abstract: Copyright protection is becoming an important issue for organisations that distribute digital content through e-learning applications. One of the most promising methods for copyright protection is digital watermarking, a highly demanding application in terms of CPU load. In this communication, some specific cases are presented where GRID computing could be used as an enabling/assisting technology for watermarking.

Abstract The ever-increasing use of the Internet and file sharing applications based on Peer to P... more Abstract The ever-increasing use of the Internet and file sharing applications based on Peer to Peer networks has alarmed content authors, providers and resellers of digital content. Techniques proposed for protecting digital media include watermarking, use of metadata and self-protection and self-authentication. In this paper we review the most important of these methods and analyse their potential use in Digital Rights Management systems.