Dépouillements

Filter banks for improved LCD motion / S. Har-Noy in Signal processing. Image communication, Vol. 25 N° 1 (Janvier 2010) 

Public ISBD [article]  in Signal processing. Image communication > Vol. 25 N° 1 (Janvier 2010) . - pp. 1–9 Titre : Filter banks for improved LCD motion Type de document : texte imprimé Auteurs : S. Har-Noy, Auteur ; E. Martinez, Auteur ; T. Q. Nguyen, Auteur Année de publication : 2012 Article en page(s) : pp. 1–9 Note générale : Electronique Langues : Anglais (eng) Mots-clés : Deconvolution  Filter  bank  Video  processing  Human  visual  system  Flat  panel  displays  Liquid  crystal  displays Résumé : In the past several years much attention has been placed on improving the motion picture quality of liquid crystal displays (LCDs). One pervasive problem is motion blur which occurs due to the inherent sample-and-hold nature of LCD image formation. In this work, we take a signal processing approach to motion blur reduction by pre-processing the data before it is sent to the display. We develop a two-channel non-perfect reconstruction filter bank that is able to reduce the amount of perceivable motion blur. In addition, as in similar works, we discriminate between different regions of the scene and weight the application of the algorithm based on their susceptibility to motion blur. Perceptual tests indicate that our algorithm reduces the amount of perceivable motion blur on LCDs. ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science/article/pii/S0923596509001210 [article] Filter banks for improved LCD motion [texte imprimé] / S. Har-Noy, Auteur ; E. Martinez, Auteur ; T. Q. Nguyen, Auteur . - 2012 . - pp. 1–9. Electronique Langues : Anglais (eng) in Signal processing. Image communication > Vol. 25 N° 1 (Janvier 2010) . - pp. 1–9 Mots-clés : Deconvolution  Filter  bank  Video  processing  Human  visual  system  Flat  panel  displays  Liquid  crystal  displays Résumé : In the past several years much attention has been placed on improving the motion picture quality of liquid crystal displays (LCDs). One pervasive problem is motion blur which occurs due to the inherent sample-and-hold nature of LCD image formation. In this work, we take a signal processing approach to motion blur reduction by pre-processing the data before it is sent to the display. We develop a two-channel non-perfect reconstruction filter bank that is able to reduce the amount of perceivable motion blur. In addition, as in similar works, we discriminate between different regions of the scene and weight the application of the algorithm based on their susceptibility to motion blur. Perceptual tests indicate that our algorithm reduces the amount of perceivable motion blur on LCDs. ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science/article/pii/S0923596509001210

Secure reversible visible image watermarking with authentication / Han-Min Tsai in Signal processing. Image communication, Vol. 25 N° 1 (Janvier 2010) 

Public ISBD [article]  in Signal processing. Image communication > Vol. 25 N° 1 (Janvier 2010) . - pp. 10–17 Titre : Secure reversible visible image watermarking with authentication Type de document : texte imprimé Auteurs : Han-Min Tsai, Auteur ; Long-Wen Chang, Auteur Année de publication : 2012 Article en page(s) : pp. 10–17 Note générale : Electronique Langues : Anglais (eng) Mots-clés : Visible  watermarking  Reversible  data  embedding  Image  authentication  Lagrange  multipliers Résumé : This paper proposes a secure reversible visible watermarking approach. The proposed pixel mapping function superposes a binary watermark image on a host image to create an intermediate visible watermarked image. Meanwhile, an almost inverse function generates the recovery data for restoring the original pixels. To prevent unauthorized users from approximating the original pixels in the watermarked region, this method adds an integer sequence in the intermediate watermarked image. The sequence is composed of integers generated by two random variables having normal distributions with zero means and distinct variances. The variances facilitate a trade-off between the watermark transparency and the noise generated by unauthorized users. The proposed method also uses Lagrange multipliers to find the optimized variances for the trade-off. Finally, this method uses reversible data embedding to embed the recovery data and hash value for reversibility and authentication, respectively. Experimental results show the watermark visibility for test images along with the watermark transparency for different variances. Using the optimized variances, the watermarked image is at the balance between the watermark transparency and the unauthorized-user-generating noise. ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science/article/pii/S0923596509001325 [article] Secure reversible visible image watermarking with authentication [texte imprimé] / Han-Min Tsai, Auteur ; Long-Wen Chang, Auteur . - 2012 . - pp. 10–17. Electronique Langues : Anglais (eng) in Signal processing. Image communication > Vol. 25 N° 1 (Janvier 2010) . - pp. 10–17 Mots-clés : Visible  watermarking  Reversible  data  embedding  Image  authentication  Lagrange  multipliers Résumé : This paper proposes a secure reversible visible watermarking approach. The proposed pixel mapping function superposes a binary watermark image on a host image to create an intermediate visible watermarked image. Meanwhile, an almost inverse function generates the recovery data for restoring the original pixels. To prevent unauthorized users from approximating the original pixels in the watermarked region, this method adds an integer sequence in the intermediate watermarked image. The sequence is composed of integers generated by two random variables having normal distributions with zero means and distinct variances. The variances facilitate a trade-off between the watermark transparency and the noise generated by unauthorized users. The proposed method also uses Lagrange multipliers to find the optimized variances for the trade-off. Finally, this method uses reversible data embedding to embed the recovery data and hash value for reversibility and authentication, respectively. Experimental results show the watermark visibility for test images along with the watermark transparency for different variances. Using the optimized variances, the watermarked image is at the balance between the watermark transparency and the unauthorized-user-generating noise. ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science/article/pii/S0923596509001325

Statistical modeling and many-to-many matching for view-based 3D object retrieval / Fei Li in Signal processing. Image communication, Vol. 25 N° 1 (Janvier 2010) 

Public ISBD [article]  in Signal processing. Image communication > Vol. 25 N° 1 (Janvier 2010) . - pp. 18–27 Titre : Statistical modeling and many-to-many matching for view-based 3D object retrieval Type de document : texte imprimé Auteurs : Fei Li, Auteur ; Qionghai Dai, Auteur ; Wenli Xu, Auteur Année de publication : 2012 Article en page(s) : pp. 18–27 Note générale : Electronique Langues : Anglais (eng) Mots-clés : View-based  3D  object  retrieval  Statistical  modeling  Markov  chain  Many-to-many  matching  Earth  mover's  distance Résumé : We address the task of view-based 3D object retrieval, in which each object is represented by a set of views taken from different positions, rather than a geometrical model based on polygonal meshes. As the number of views and the view point setting cannot always be the same for different objects, the retrieval task is more challenging and the existing methods for 3D model retrieval are infeasible. In this paper, the information in the sets of views is exploited from two aspects. On the one hand, the form of histogram is converted from vector to state sequence, and Markov chain (MC) is utilized for modeling the statistical characteristics of all the views representing the same object. On the other hand, the earth mover's distance (EMD) is involved to achieve many-to-many matching between two sets of views. For 3D object retrieval, by combining the above two aspects together, a new distance measure is defined, and a novel approach to automatically determine the edge weights in graph-based semi-supervised learning is proposed. Experimental results on different databases demonstrate the effectiveness of our proposal. ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science/article/pii/S0923596509001313 [article] Statistical modeling and many-to-many matching for view-based 3D object retrieval [texte imprimé] / Fei Li, Auteur ; Qionghai Dai, Auteur ; Wenli Xu, Auteur . - 2012 . - pp. 18–27. Electronique Langues : Anglais (eng) in Signal processing. Image communication > Vol. 25 N° 1 (Janvier 2010) . - pp. 18–27 Mots-clés : View-based  3D  object  retrieval  Statistical  modeling  Markov  chain  Many-to-many  matching  Earth  mover's  distance Résumé : We address the task of view-based 3D object retrieval, in which each object is represented by a set of views taken from different positions, rather than a geometrical model based on polygonal meshes. As the number of views and the view point setting cannot always be the same for different objects, the retrieval task is more challenging and the existing methods for 3D model retrieval are infeasible. In this paper, the information in the sets of views is exploited from two aspects. On the one hand, the form of histogram is converted from vector to state sequence, and Markov chain (MC) is utilized for modeling the statistical characteristics of all the views representing the same object. On the other hand, the earth mover's distance (EMD) is involved to achieve many-to-many matching between two sets of views. For 3D object retrieval, by combining the above two aspects together, a new distance measure is defined, and a novel approach to automatically determine the edge weights in graph-based semi-supervised learning is proposed. Experimental results on different databases demonstrate the effectiveness of our proposal. ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science/article/pii/S0923596509001313

A study of relative phase in complex wavelet domain: Property, statistics and applications in texture image retrieval and segmentation / An Vo in Signal processing. Image communication, Vol. 25 N° 1 (Janvier 2010) 

Public ISBD [article]  in Signal processing. Image communication > Vol. 25 N° 1 (Janvier 2010) . - pp. 28–46 Titre : A study of relative phase in complex wavelet domain: Property, statistics and applications in texture image retrieval and segmentation Type de document : texte imprimé Auteurs : An Vo, Auteur ; Soontorn Oraintara, Auteur Année de publication : 2012 Article en page(s) : pp. 28–46 Note générale : Electronique Langues : Anglais (eng) Mots-clés : Relative  phase  Statistics  of  relative  phase  Pdf  of  relative  phase  Statistical  image  modeling  Von  Mises  distribution  Wrapped  Cauchy  distribution  Pyramidal  dual-tree  directional  filter  bank  Dual-tree  complex  wavelet  transform  Uniform  discrete  curvelet  transform  Texture  image  retrieval  Texture  segmentation Résumé : In this paper, we develop a new approach which exploits the probabilistic properties from the phase information of 2-D complex wavelet coefficients for image modeling. Instead of directly using phases of complex wavelet coefficients, we demonstrate why relative phases should be used. The definition, properties and statistics of relative phases of complex coefficients are studied in detail. We proposed von Mises and wrapped Cauchy for the probability density function (pdf) of relative phases in the complex wavelet domain. The maximum-likelihood method is used to estimate two parameters of von Mises and wrapped Cauchy. We demonstrate that the von Mises and wrapped Cauchy fit well with real data obtained from various real images including texture images as well as standard images. The von Mises and wrapped Cauchy models are compared, and the simulation results show that the wrapped Cauchy fits well with the peaky and heavy-tailed pdf of relative phases and the von Mises fits well with the pdf which is in Gaussian shape. For most of the test images, the wrapped Cauchy model is more accurate than the von Mises model, when images are decomposed by different complex wavelet transforms including dual-tree complex wavelet (DTCWT), pyramidal dual-tree directional filter bank (PDTDFB) and uniform discrete curvelet transform (UDCT). Moreover, the relative phase is applied to obtain new features for texture image retrieval and segmentation applications. Instead of using only real or magnitude coefficients, the new approach uses a feature in which phase information is incorporated, yielding a higher accuracy in texture image retrieval as well as in segmentation. The relative phase information which is complementary to the magnitude is a promising approach in image processing. ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science/article/pii/S0923596509001192# [article] A study of relative phase in complex wavelet domain: Property, statistics and applications in texture image retrieval and segmentation [texte imprimé] / An Vo, Auteur ; Soontorn Oraintara, Auteur . - 2012 . - pp. 28–46. Electronique Langues : Anglais (eng) in Signal processing. Image communication > Vol. 25 N° 1 (Janvier 2010) . - pp. 28–46 Mots-clés : Relative  phase  Statistics  of  relative  phase  Pdf  of  relative  phase  Statistical  image  modeling  Von  Mises  distribution  Wrapped  Cauchy  distribution  Pyramidal  dual-tree  directional  filter  bank  Dual-tree  complex  wavelet  transform  Uniform  discrete  curvelet  transform  Texture  image  retrieval  Texture  segmentation Résumé : In this paper, we develop a new approach which exploits the probabilistic properties from the phase information of 2-D complex wavelet coefficients for image modeling. Instead of directly using phases of complex wavelet coefficients, we demonstrate why relative phases should be used. The definition, properties and statistics of relative phases of complex coefficients are studied in detail. We proposed von Mises and wrapped Cauchy for the probability density function (pdf) of relative phases in the complex wavelet domain. The maximum-likelihood method is used to estimate two parameters of von Mises and wrapped Cauchy. We demonstrate that the von Mises and wrapped Cauchy fit well with real data obtained from various real images including texture images as well as standard images. The von Mises and wrapped Cauchy models are compared, and the simulation results show that the wrapped Cauchy fits well with the peaky and heavy-tailed pdf of relative phases and the von Mises fits well with the pdf which is in Gaussian shape. For most of the test images, the wrapped Cauchy model is more accurate than the von Mises model, when images are decomposed by different complex wavelet transforms including dual-tree complex wavelet (DTCWT), pyramidal dual-tree directional filter bank (PDTDFB) and uniform discrete curvelet transform (UDCT). Moreover, the relative phase is applied to obtain new features for texture image retrieval and segmentation applications. Instead of using only real or magnitude coefficients, the new approach uses a feature in which phase information is incorporated, yielding a higher accuracy in texture image retrieval as well as in segmentation. The relative phase information which is complementary to the magnitude is a promising approach in image processing. ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science/article/pii/S0923596509001192#

Successive refinement based Wyner–Ziv video compression / Xiaopeng Fan in Signal processing. Image communication, Vol. 25 N° 1 (Janvier 2010) 

Public ISBD [article]  in Signal processing. Image communication > Vol. 25 N° 1 (Janvier 2010) . - pp. 47–63 Titre : Successive refinement based Wyner–Ziv video compression Type de document : texte imprimé Auteurs : Xiaopeng Fan, Auteur ; Oscar C. Au, Auteur ; Ngai Man Cheung, Auteur Année de publication : 2012 Article en page(s) : pp. 47–63 Note générale : Electronique Langues : Anglais (eng) Mots-clés : Wyner–Ziv  Successive  refinement  Subsample  Rate  distortion  analysis Résumé : Wyner–Ziv coding enables low complexity video encoding with the motion estimation procedure shifted to the decoder. However, the accuracy of decoder motion estimation is often low, due to the absence of the input source frame (at the decoder). In this paper, we propose a novel Wyner–Ziv successive refinement approach to improve the motion compensation accuracy and the overall compression efficiency of Wyner–Ziv video coding. Our approach encodes each frame by multiple Wyner–Ziv coding layers and uses the progressively refined reconstruction frame to guide the motion estimation for progressively improved accuracy. The proposed approach yields competitive results against state-of-the-art low complexity Wyner–Ziv video coding approaches, and can gain up to 3.8 dB over the conventional Wyner–Ziv video coding approach and up to 1.5 dB over the previous bitplane-based refinement approach. Furthermore, this paper also presents the rate distortion analysis and the performance comparison of the proposed approach and conventional approaches. The rate distortion performance loss (due to performing decoder motion estimation) is at most 2.17 dB (or equivalently nats/pixel) in our scheme according to our analysis, but can be more than 6 dB in the conventional approach according to previous research. For the simplified two-layers case of our approach, we derive the optimal subsampling ratio in the sense of rate distortion performance. We also extend our analysis and conclusions from P frame to B frame. Finally, we verify our analysis by experimental results. ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science/article/pii/S0923596509001209 [article] Successive refinement based Wyner–Ziv video compression [texte imprimé] / Xiaopeng Fan, Auteur ; Oscar C. Au, Auteur ; Ngai Man Cheung, Auteur . - 2012 . - pp. 47–63. Electronique Langues : Anglais (eng) in Signal processing. Image communication > Vol. 25 N° 1 (Janvier 2010) . - pp. 47–63 Mots-clés : Wyner–Ziv  Successive  refinement  Subsample  Rate  distortion  analysis Résumé : Wyner–Ziv coding enables low complexity video encoding with the motion estimation procedure shifted to the decoder. However, the accuracy of decoder motion estimation is often low, due to the absence of the input source frame (at the decoder). In this paper, we propose a novel Wyner–Ziv successive refinement approach to improve the motion compensation accuracy and the overall compression efficiency of Wyner–Ziv video coding. Our approach encodes each frame by multiple Wyner–Ziv coding layers and uses the progressively refined reconstruction frame to guide the motion estimation for progressively improved accuracy. The proposed approach yields competitive results against state-of-the-art low complexity Wyner–Ziv video coding approaches, and can gain up to 3.8 dB over the conventional Wyner–Ziv video coding approach and up to 1.5 dB over the previous bitplane-based refinement approach. Furthermore, this paper also presents the rate distortion analysis and the performance comparison of the proposed approach and conventional approaches. The rate distortion performance loss (due to performing decoder motion estimation) is at most 2.17 dB (or equivalently nats/pixel) in our scheme according to our analysis, but can be more than 6 dB in the conventional approach according to previous research. For the simplified two-layers case of our approach, we derive the optimal subsampling ratio in the sense of rate distortion performance. We also extend our analysis and conclusions from P frame to B frame. Finally, we verify our analysis by experimental results. ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science/article/pii/S0923596509001209

Mutual information-based context quantization / Marco Cagnazzo in Signal processing. Image communication, Vol. 25 N° 1 (Janvier 2010) 

Public ISBD [article]  in Signal processing. Image communication > Vol. 25 N° 1 (Janvier 2010) . - pp. 64–74 Titre : Mutual information-based context quantization Type de document : texte imprimé Auteurs : Marco Cagnazzo, Auteur ; Marc Antonini, Auteur ; Michel Barlaud, Auteur Année de publication : 2012 Article en page(s) : pp. 64–74 Note générale : Electronique Langues : Anglais (eng) Mots-clés : Lossless  coding  Context  dilution  Context  quantization Résumé : Context-based lossless coding suffers in many cases from the so-called context dilution problem, which arises when, in order to model high-order statistic dependencies among data, a large number of contexts is used. In this case the learning process cannot be fed with enough data, and so the probability estimation is not reliable. To avoid this problem, state-of-the-art algorithms for lossless image coding resort to context quantization (CQ) into a few conditioning states, whose statistics are easier to estimate in a reliable way. It has been early recognized that in order to achieve the best compression ratio, contexts have to be grouped according to a maximal mutual information criterion. This leads to quantization algorithms which are able to determine a local minimum of the coding cost in the general case, and even the global minimum in the case of binary-valued input. This paper surveys the CQ problem and provides a detailed analytical formulation of it, allowing to shed light on some details of the optimization process. As a consequence we find that state-of-the-art algorithms have a suboptimal step. The proposed approach allows a steeper path toward the cost function minimum. Moreover, some sufficient conditions are found that allow to find a globally optimal solution even when the input alphabet is not binary. Even though the paper mainly focuses on the theoretical aspects of CQ, a number of experiments to validate the proposed method have been performed (for the special case of segmentation map lossless coding), and encouraging results have been recorded. ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science/article/pii/S0923596509001180 [article] Mutual information-based context quantization [texte imprimé] / Marco Cagnazzo, Auteur ; Marc Antonini, Auteur ; Michel Barlaud, Auteur . - 2012 . - pp. 64–74. Electronique Langues : Anglais (eng) in Signal processing. Image communication > Vol. 25 N° 1 (Janvier 2010) . - pp. 64–74 Mots-clés : Lossless  coding  Context  dilution  Context  quantization Résumé : Context-based lossless coding suffers in many cases from the so-called context dilution problem, which arises when, in order to model high-order statistic dependencies among data, a large number of contexts is used. In this case the learning process cannot be fed with enough data, and so the probability estimation is not reliable. To avoid this problem, state-of-the-art algorithms for lossless image coding resort to context quantization (CQ) into a few conditioning states, whose statistics are easier to estimate in a reliable way. It has been early recognized that in order to achieve the best compression ratio, contexts have to be grouped according to a maximal mutual information criterion. This leads to quantization algorithms which are able to determine a local minimum of the coding cost in the general case, and even the global minimum in the case of binary-valued input. This paper surveys the CQ problem and provides a detailed analytical formulation of it, allowing to shed light on some details of the optimization process. As a consequence we find that state-of-the-art algorithms have a suboptimal step. The proposed approach allows a steeper path toward the cost function minimum. Moreover, some sufficient conditions are found that allow to find a globally optimal solution even when the input alphabet is not binary. Even though the paper mainly focuses on the theoretical aspects of CQ, a number of experiments to validate the proposed method have been performed (for the special case of segmentation map lossless coding), and encouraging results have been recorded. ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science/article/pii/S0923596509001180

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