Dépouillements

Reduced-reference metric design for objective perceptual quality assessment in wireless imaging / Ulrich Engelke in Signal processing. Image communication, Vol. 24 N° 7 (Août 2009) 

Public ISBD [article]  in Signal processing. Image communication > Vol. 24 N° 7 (Août 2009) . - pp. 525-547 Titre : Reduced-reference metric design for objective perceptual quality assessment in wireless imaging Type de document : texte imprimé Auteurs : Ulrich Engelke, Auteur ; Maulana Kusuma, Auteur ; Hans-Jürgen Zepernick, Auteur Article en page(s) : pp. 525-547 Note générale : Electronique Langues : Anglais (eng) Mots-clés : Objective  perceptual  image  quality  Normalized  hybrid  image  quality  metric  Perceptual  relevance  weighted  Lp-norm  Reduced-reference  Wireless  imaging Index. décimale : 621.382 Dispositifs électroniques utilisant les effets des corps solides. Dispositifs semi-conducteurs Résumé : The rapid growth of third and development of future generation mobile systems has led to an increase in the demand for image and video services. However, the hostile nature of the wireless channel makes the deployment of such services much more challenging, as in the case of a wireline system. In this context, the importance of taking care of user satisfaction with service provisioning as a whole has been recognized. The related user-oriented quality concepts cover end-to-end quality of service and subjective factors such as experiences with the service. To monitor quality and adapt system resources, performance indicators that represent service integrity have to be selected and related to objective measures that correlate well with the quality as perceived by humans. Such objective perceptual quality metrics can then be utilized to optimize quality perception associated with applications in technical systems. In this paper, we focus on the design of reduced-reference objective perceptual image quality metrics for use in wireless imaging. Specifically, the normalized hybrid image quality metric (NHIQM) and a perceptual relevance weighted Lp-norm are designed. The main idea behind both feature-based metrics relates to the fact that the human visual system (HVS) is trained to extract structural information from the viewing area. Accordingly, NHIQM and Lp-norm are designed to account for different structural artifacts that have been observed in our distortion model of a wireless link. The extent by which individual artifacts are present in a given image is obtained by measuring related image features. The overall quality measure is then computed as a weighting sum of the features with the respective perceptual relevance weight obtained from subjective experiments. The proposed metrics differ mainly in the pooling of the features and amount of reduced-reference produced. While NHIQM performs the pooling at the transmitter of the system to produce a single value as reduced-reference, the Lp-norm requires all involved feature values from the transmitted and received image to perform the pooling on the feature differences at the receiver. In addition, non-linear mapping functions are developed that relate the metric values to predicted mean opinion scores (MOS) and account for saturations in the HVS. The evaluation of prediction performance of NHIQM and the Lp-norm reveals their excellent correlation with human perception in terms of accuracy, monotonicity, and consistency. This holds not only for the prediction performance on images taken for the training of the metrics but also for the generalization to unknown images. In addition, it is shown that the NHIQM approach and the perceptual relevance weighted Lp-norm outperform other prominent objective quality metrics in prediction performance. DEWEY : 361.382 ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235640%23 [...] [article] Reduced-reference metric design for objective perceptual quality assessment in wireless imaging [texte imprimé] / Ulrich Engelke, Auteur ; Maulana Kusuma, Auteur ; Hans-Jürgen Zepernick, Auteur . - pp. 525-547. Electronique Langues : Anglais (eng) in Signal processing. Image communication > Vol. 24 N° 7 (Août 2009) . - pp. 525-547 Mots-clés : Objective  perceptual  image  quality  Normalized  hybrid  image  quality  metric  Perceptual  relevance  weighted  Lp-norm  Reduced-reference  Wireless  imaging Index. décimale : 621.382 Dispositifs électroniques utilisant les effets des corps solides. Dispositifs semi-conducteurs Résumé : The rapid growth of third and development of future generation mobile systems has led to an increase in the demand for image and video services. However, the hostile nature of the wireless channel makes the deployment of such services much more challenging, as in the case of a wireline system. In this context, the importance of taking care of user satisfaction with service provisioning as a whole has been recognized. The related user-oriented quality concepts cover end-to-end quality of service and subjective factors such as experiences with the service. To monitor quality and adapt system resources, performance indicators that represent service integrity have to be selected and related to objective measures that correlate well with the quality as perceived by humans. Such objective perceptual quality metrics can then be utilized to optimize quality perception associated with applications in technical systems. In this paper, we focus on the design of reduced-reference objective perceptual image quality metrics for use in wireless imaging. Specifically, the normalized hybrid image quality metric (NHIQM) and a perceptual relevance weighted Lp-norm are designed. The main idea behind both feature-based metrics relates to the fact that the human visual system (HVS) is trained to extract structural information from the viewing area. Accordingly, NHIQM and Lp-norm are designed to account for different structural artifacts that have been observed in our distortion model of a wireless link. The extent by which individual artifacts are present in a given image is obtained by measuring related image features. The overall quality measure is then computed as a weighting sum of the features with the respective perceptual relevance weight obtained from subjective experiments. The proposed metrics differ mainly in the pooling of the features and amount of reduced-reference produced. While NHIQM performs the pooling at the transmitter of the system to produce a single value as reduced-reference, the Lp-norm requires all involved feature values from the transmitted and received image to perform the pooling on the feature differences at the receiver. In addition, non-linear mapping functions are developed that relate the metric values to predicted mean opinion scores (MOS) and account for saturations in the HVS. The evaluation of prediction performance of NHIQM and the Lp-norm reveals their excellent correlation with human perception in terms of accuracy, monotonicity, and consistency. This holds not only for the prediction performance on images taken for the training of the metrics but also for the generalization to unknown images. In addition, it is shown that the NHIQM approach and the perceptual relevance weighted Lp-norm outperform other prominent objective quality metrics in prediction performance. DEWEY : 361.382 ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235640%23 [...]

Perceivable artifacts in compressed video and their relation to video quality / Jun Xia in Signal processing. Image communication, Vol. 24 N° 7 (Août 2009) 

Public ISBD [article]  in Signal processing. Image communication > Vol. 24 N° 7 (Août 2009) . - pp. 548-556 Titre : Perceivable artifacts in compressed video and their relation to video quality Type de document : texte imprimé Auteurs : Jun Xia, Auteur ; Yue Shi, Auteur ; Kees Teunissen, Auteur Article en page(s) : pp. 548-556 Note générale : Electronique Langues : Anglais (eng) Mots-clés : Image  quality  Video  compression  Objective  metric  Compression  artifact Index. décimale : 621.382 Dispositifs électroniques utilisant les effets des corps solides. Dispositifs semi-conducteurs Résumé : Compressed video is degraded in quality due to the introduction of coding artifacts. A two-step subjective experiment was performed to evaluate the most visible artifacts and their relation to video quality for AVS and H.264 compressed video. In the first step, non-expert viewers were requested to score the image quality degradation as a function of compression ratio for various video sequences and to indicate which artifact was perceived during scoring. During the second step, eight trained viewers were asked to score the strength of three artifacts, i.e., blurring, blocking, and color distortion, which were reported as the most perceivable artifacts in the first step of the experiment. The quality performance between AVS and H.264 was also compared. The analysis of covariance indicated that the quality performance between AVS and H.264 was very close. A linear regression analysis showed that for the CIF videos 96% of the variance in quality degradation could be predicted by linearly combining the normalized strengths of the three most visible artifacts. DEWEY : 361.382 ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235640%23 [...] [article] Perceivable artifacts in compressed video and their relation to video quality [texte imprimé] / Jun Xia, Auteur ; Yue Shi, Auteur ; Kees Teunissen, Auteur . - pp. 548-556. Electronique Langues : Anglais (eng) in Signal processing. Image communication > Vol. 24 N° 7 (Août 2009) . - pp. 548-556 Mots-clés : Image  quality  Video  compression  Objective  metric  Compression  artifact Index. décimale : 621.382 Dispositifs électroniques utilisant les effets des corps solides. Dispositifs semi-conducteurs Résumé : Compressed video is degraded in quality due to the introduction of coding artifacts. A two-step subjective experiment was performed to evaluate the most visible artifacts and their relation to video quality for AVS and H.264 compressed video. In the first step, non-expert viewers were requested to score the image quality degradation as a function of compression ratio for various video sequences and to indicate which artifact was perceived during scoring. During the second step, eight trained viewers were asked to score the strength of three artifacts, i.e., blurring, blocking, and color distortion, which were reported as the most perceivable artifacts in the first step of the experiment. The quality performance between AVS and H.264 was also compared. The analysis of covariance indicated that the quality performance between AVS and H.264 was very close. A linear regression analysis showed that for the CIF videos 96% of the variance in quality degradation could be predicted by linearly combining the normalized strengths of the three most visible artifacts. DEWEY : 361.382 ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235640%23 [...]

Spatiotemporal saliency for video classification / Konstantinos Rapantzikos in Signal processing. Image communication, Vol. 24 N° 7 (Août 2009) 

Public ISBD [article]  in Signal processing. Image communication > Vol. 24 N° 7 (Août 2009) . - pp. 557-571 Titre : Spatiotemporal saliency for video classification Type de document : texte imprimé Auteurs : Konstantinos Rapantzikos, Auteur ; Nicolas Tsapatsoulis, Auteur ; Yannis Avrithis, Auteur Article en page(s) : pp. 557-571 Note générale : Electronique Langues : Anglais (eng) Mots-clés : Spatiotemporal  visual  saliency  Video  classification Index. décimale : 621.382 Dispositifs électroniques utilisant les effets des corps solides. Dispositifs semi-conducteurs Résumé : Computer vision applications often need to process only a representative part of the visual input rather than the whole image/sequence. Considerable research has been carried out into salient region detection methods based either on models emulating human visual attention (VA) mechanisms or on computational approximations. Most of the proposed methods are bottom-up and their major goal is to filter out redundant visual information. In this paper, we propose and elaborate on a saliency detection model that treats a video sequence as a spatiotemporal volume and generates a local saliency measure for each visual unit (voxel). This computation involves an optimization process incorporating inter- and intra-feature competition at the voxel level. Perceptual decomposition of the input, spatiotemporal center-surround interactions and the integration of heterogeneous feature conspicuity values are described and an experimental framework for video classification is set up. This framework consists of a series of experiments that shows the effect of saliency in classification performance and let us draw conclusions on how well the detected salient regions represent the visual input. A comparison is attempted that shows the potential of the proposed method. DEWEY : 361.382 ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235640%23 [...] [article] Spatiotemporal saliency for video classification [texte imprimé] / Konstantinos Rapantzikos, Auteur ; Nicolas Tsapatsoulis, Auteur ; Yannis Avrithis, Auteur . - pp. 557-571. Electronique Langues : Anglais (eng) in Signal processing. Image communication > Vol. 24 N° 7 (Août 2009) . - pp. 557-571 Mots-clés : Spatiotemporal  visual  saliency  Video  classification Index. décimale : 621.382 Dispositifs électroniques utilisant les effets des corps solides. Dispositifs semi-conducteurs Résumé : Computer vision applications often need to process only a representative part of the visual input rather than the whole image/sequence. Considerable research has been carried out into salient region detection methods based either on models emulating human visual attention (VA) mechanisms or on computational approximations. Most of the proposed methods are bottom-up and their major goal is to filter out redundant visual information. In this paper, we propose and elaborate on a saliency detection model that treats a video sequence as a spatiotemporal volume and generates a local saliency measure for each visual unit (voxel). This computation involves an optimization process incorporating inter- and intra-feature competition at the voxel level. Perceptual decomposition of the input, spatiotemporal center-surround interactions and the integration of heterogeneous feature conspicuity values are described and an experimental framework for video classification is set up. This framework consists of a series of experiments that shows the effect of saliency in classification performance and let us draw conclusions on how well the detected salient regions represent the visual input. A comparison is attempted that shows the potential of the proposed method. DEWEY : 361.382 ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235640%23 [...]

Farthest point distance / Akrem El-ghazal in Signal processing. Image communication, Vol. 24 N° 7 (Août 2009) 

Public ISBD [article]  in Signal processing. Image communication > Vol. 24 N° 7 (Août 2009) . - pp. 572-586 Titre : Farthest point distance : a new shape signature for Fourier descriptors Type de document : texte imprimé Auteurs : Akrem El-ghazal, Auteur ; Otman Basir, Auteur ; Saeid Belkasim, Auteur Article en page(s) : pp. 572-586 Note générale : Electronique Langues : Anglais (eng) Mots-clés : Fourier  descriptors  Image  retrieval  Shape  signatures Index. décimale : 621.382 Dispositifs électroniques utilisant les effets des corps solides. Dispositifs semi-conducteurs Résumé : Shape description is an important task in content-based image retrieval (CBIR). A variety of techniques have been reported in the literature that aims to represent objects based on their shapes. Each of these techniques has its pros and cons. Fourier descriptor (FD) is one of these techniques a simple, yet powerful technique that offers attractive properties such as rotational, scale, and translational invariance. Shape signatures, which constitute an essential component of Fourier descriptors, reduce 2-D shapes to 1-D functions and hence facilitate the process of deriving invariant shape features using the Fourier transform. A good number of shape signatures have been reported in the literature. These shape signatures lack important shape information, such as corners, in their representations. This information plays a major role in distinguishing between different shapes. In this paper, we present the farthest point distance (FPD), a novel shape signature that includes corner information to enhance the performance of shape retrieval using Fourier descriptors. The signature is calculated at each point on a shape contour. This signature yields distances calculated between the different shape corners, and captures points within the shape at which the human focuses visual attention in order to classify shapes. To reach a comprehensive conclusion about the merit of the proposed signature, the signature is compared against eight popular signatures using the well-known MPEG-7 database. Furthermore, the proposed signature is evaluated against standard boundary- and region-based techniques: the curvature scale space (CSS) and the Zernike moments (ZM). The FPD signature has demonstrated superior overall performance compared with the other eight signatures and the two standard techniques. DEWEY : 361.382 ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235640%23 [...] [article] Farthest point distance : a new shape signature for Fourier descriptors [texte imprimé] / Akrem El-ghazal, Auteur ; Otman Basir, Auteur ; Saeid Belkasim, Auteur . - pp. 572-586. Electronique Langues : Anglais (eng) in Signal processing. Image communication > Vol. 24 N° 7 (Août 2009) . - pp. 572-586 Mots-clés : Fourier  descriptors  Image  retrieval  Shape  signatures Index. décimale : 621.382 Dispositifs électroniques utilisant les effets des corps solides. Dispositifs semi-conducteurs Résumé : Shape description is an important task in content-based image retrieval (CBIR). A variety of techniques have been reported in the literature that aims to represent objects based on their shapes. Each of these techniques has its pros and cons. Fourier descriptor (FD) is one of these techniques a simple, yet powerful technique that offers attractive properties such as rotational, scale, and translational invariance. Shape signatures, which constitute an essential component of Fourier descriptors, reduce 2-D shapes to 1-D functions and hence facilitate the process of deriving invariant shape features using the Fourier transform. A good number of shape signatures have been reported in the literature. These shape signatures lack important shape information, such as corners, in their representations. This information plays a major role in distinguishing between different shapes. In this paper, we present the farthest point distance (FPD), a novel shape signature that includes corner information to enhance the performance of shape retrieval using Fourier descriptors. The signature is calculated at each point on a shape contour. This signature yields distances calculated between the different shape corners, and captures points within the shape at which the human focuses visual attention in order to classify shapes. To reach a comprehensive conclusion about the merit of the proposed signature, the signature is compared against eight popular signatures using the well-known MPEG-7 database. Furthermore, the proposed signature is evaluated against standard boundary- and region-based techniques: the curvature scale space (CSS) and the Zernike moments (ZM). The FPD signature has demonstrated superior overall performance compared with the other eight signatures and the two standard techniques. DEWEY : 361.382 ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235640%23 [...]

Fragile watermarking using finite field trigonometrical transforms / R. J. Cintra in Signal processing. Image communication, Vol. 24 N° 7 (Août 2009) 

Public ISBD [article]  in Signal processing. Image communication > Vol. 24 N° 7 (Août 2009) . - pp. 587-597 Titre : Fragile watermarking using finite field trigonometrical transforms Type de document : texte imprimé Auteurs : R. J. Cintra, Auteur ; V.S. Dimitrov, Auteur ; H.M. de Oliveira, Auteur Article en page(s) : pp. 587-597 Note générale : Electronique Langues : Anglais (eng) Mots-clés : Fragile  watermarking  Number  theoretic  transforms  Finite  field  trigonometry Index. décimale : 621.382 Dispositifs électroniques utilisant les effets des corps solides. Dispositifs semi-conducteurs Résumé : Fragile digital watermarking has been applied for authentication and alteration detection in images. Utilizing the cosine and Hartley transforms over finite fields, a new transform domain fragile watermarking scheme is introduced. A watermark is embedded into a host image via a blockwise application of two-dimensional finite field cosine or Hartley transforms. Additionally, the considered finite field transforms are adjusted to be number theoretic transforms, appropriate for error-free calculation. The employed technique can provide invisible fragile watermarking for authentication systems with tamper location capability. It is shown that the choice of the finite field characteristic is pivotal to obtain perceptually invisible watermarked images. It is also shown that the generated watermarked images can be used as publicly available signature data for authentication purposes. DEWEY : 361.382 ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235640%23 [...] [article] Fragile watermarking using finite field trigonometrical transforms [texte imprimé] / R. J. Cintra, Auteur ; V.S. Dimitrov, Auteur ; H.M. de Oliveira, Auteur . - pp. 587-597. Electronique Langues : Anglais (eng) in Signal processing. Image communication > Vol. 24 N° 7 (Août 2009) . - pp. 587-597 Mots-clés : Fragile  watermarking  Number  theoretic  transforms  Finite  field  trigonometry Index. décimale : 621.382 Dispositifs électroniques utilisant les effets des corps solides. Dispositifs semi-conducteurs Résumé : Fragile digital watermarking has been applied for authentication and alteration detection in images. Utilizing the cosine and Hartley transforms over finite fields, a new transform domain fragile watermarking scheme is introduced. A watermark is embedded into a host image via a blockwise application of two-dimensional finite field cosine or Hartley transforms. Additionally, the considered finite field transforms are adjusted to be number theoretic transforms, appropriate for error-free calculation. The employed technique can provide invisible fragile watermarking for authentication systems with tamper location capability. It is shown that the choice of the finite field characteristic is pivotal to obtain perceptually invisible watermarked images. It is also shown that the generated watermarked images can be used as publicly available signature data for authentication purposes. DEWEY : 361.382 ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235640%23 [...]

Semantic video fingerprinting and retrieval using face information / Costas Cotsaces in Signal processing. Image communication, Vol. 24 N° 7 (Août 2009) 

Public ISBD [article]  in Signal processing. Image communication > Vol. 24 N° 7 (Août 2009) . - pp. 598-613 Titre : Semantic video fingerprinting and retrieval using face information Type de document : texte imprimé Auteurs : Costas Cotsaces, Auteur ; Nikos Nikolaidis, Auteur ; Ioannis Pitas, Auteur Article en page(s) : pp. 598-613 Note générale : Electronique Langues : Anglais (eng) Mots-clés : Video  fingerprinting  Video  retrieval  Face  recognition  Semantic  features Index. décimale : 621.382 Dispositifs électroniques utilisant les effets des corps solides. Dispositifs semi-conducteurs Résumé : The management of large video databases, especially those containing motion picture and television data, is a major contemporary challenge. A very significant tool for this management is the ability to retrieve those segments that are perceptually similar to a query segment. Another similar but equally important task is determining if a query segment is a (possibly modified) copy of part of a video in the database. The basic way to perform these two tasks is to characterize each video segment with a unique representation called a signature. Using semantic information for the construction of the signatures is a good way to ensure robustness in retrieval and fingerprinting. Here a ubiquitous semantic feature, namely the existence and identity of human faces, will be used to construct the signature. A fast algorithm has been developed to quickly and robustly perform these two tasks on very large video databases. The prerequisite face recognition was performed by a commercial system. Having verified the basic efficacy of our algorithm on a database of real video from motion pictures and television series, we then proceed to further explore its performance in an artificial digital video database, which was created using a probabilistic model of the video creation process. This enabled us to explore variations in performance based on parameters that were impossible to control in a real video database. Furthermore, the suitability of the proposed approach for very large databases was tested using (artificial) data corresponding to hundreds or thousands of hours of video. DEWEY : 361.382 ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235640%23 [...] [article] Semantic video fingerprinting and retrieval using face information [texte imprimé] / Costas Cotsaces, Auteur ; Nikos Nikolaidis, Auteur ; Ioannis Pitas, Auteur . - pp. 598-613. Electronique Langues : Anglais (eng) in Signal processing. Image communication > Vol. 24 N° 7 (Août 2009) . - pp. 598-613 Mots-clés : Video  fingerprinting  Video  retrieval  Face  recognition  Semantic  features Index. décimale : 621.382 Dispositifs électroniques utilisant les effets des corps solides. Dispositifs semi-conducteurs Résumé : The management of large video databases, especially those containing motion picture and television data, is a major contemporary challenge. A very significant tool for this management is the ability to retrieve those segments that are perceptually similar to a query segment. Another similar but equally important task is determining if a query segment is a (possibly modified) copy of part of a video in the database. The basic way to perform these two tasks is to characterize each video segment with a unique representation called a signature. Using semantic information for the construction of the signatures is a good way to ensure robustness in retrieval and fingerprinting. Here a ubiquitous semantic feature, namely the existence and identity of human faces, will be used to construct the signature. A fast algorithm has been developed to quickly and robustly perform these two tasks on very large video databases. The prerequisite face recognition was performed by a commercial system. Having verified the basic efficacy of our algorithm on a database of real video from motion pictures and television series, we then proceed to further explore its performance in an artificial digital video database, which was created using a probabilistic model of the video creation process. This enabled us to explore variations in performance based on parameters that were impossible to control in a real video database. Furthermore, the suitability of the proposed approach for very large databases was tested using (artificial) data corresponding to hundreds or thousands of hours of video. DEWEY : 361.382 ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235640%23 [...]

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