Documents disponibles écrits par cet auteur

Exploiting quantization and spatial correlation in virtual-noise modeling for distributed video coding / Jozef Škorupa in Signal processing. Image communication, Vol. 25 N° 9 (Octobre 2010) 

Public ISBD [article]  in Signal processing. Image communication > Vol. 25 N° 9 (Octobre 2010) . - pp. 674–686 Titre : Exploiting quantization and spatial correlation in virtual-noise modeling for distributed video coding Type de document : texte imprimé Auteurs : Jozef Škorupa, Auteur ; Jürgen Slowack, Auteur ; Stefaan Mys, Auteur Année de publication : 2012 Article en page(s) : pp. 674–686 Note générale : Electronique Langues : Anglais (eng) Mots-clés : Context  adaptive  Distributed  video  coding  Virtual-noise  modeling Résumé : Aiming for low-complexity encoding, video coders based on Wyner–Ziv theory are still unsuccessfully trying to match the performance of predictive video coders. One of the most important factors concerning the coding performance of distributed coders is modeling and estimating the correlation between the original video signal and its temporal prediction generated at the decoder. One of the problems of the state-of-the-art correlation estimators is that their performance is not consistent across a wide range of video content and different coding settings. To address this problem we have developed a correlation model able to adapt to changes in the content and the coding parameters by exploiting the spatial correlation of the video signal and the quantization distortion. In this paper we describe our model and present experiments showing that our model provides average bit rate gains of up to 12% and average PSNR gains of up to 0.5 dB when compared to the state-of-the-art models. The experiments suggest that the performance of distributed coders can be significantly improved by taking video content and coding parameters into account. ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science/article/pii/S092359651000055X [article] Exploiting quantization and spatial correlation in virtual-noise modeling for distributed video coding [texte imprimé] / Jozef Škorupa, Auteur ; Jürgen Slowack, Auteur ; Stefaan Mys, Auteur . - 2012 . - pp. 674–686. Electronique Langues : Anglais (eng) in Signal processing. Image communication > Vol. 25 N° 9 (Octobre 2010) . - pp. 674–686 Mots-clés : Context  adaptive  Distributed  video  coding  Virtual-noise  modeling Résumé : Aiming for low-complexity encoding, video coders based on Wyner–Ziv theory are still unsuccessfully trying to match the performance of predictive video coders. One of the most important factors concerning the coding performance of distributed coders is modeling and estimating the correlation between the original video signal and its temporal prediction generated at the decoder. One of the problems of the state-of-the-art correlation estimators is that their performance is not consistent across a wide range of video content and different coding settings. To address this problem we have developed a correlation model able to adapt to changes in the content and the coding parameters by exploiting the spatial correlation of the video signal and the quantization distortion. In this paper we describe our model and present experiments showing that our model provides average bit rate gains of up to 12% and average PSNR gains of up to 0.5 dB when compared to the state-of-the-art models. The experiments suggest that the performance of distributed coders can be significantly improved by taking video content and coding parameters into account. ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science/article/pii/S092359651000055X

Flexible distribution of complexity by hybrid predictive-distributed video coding / Jürgen Slowack in Signal processing. Image communication, Vol. 25 N° 2 (02 EX.) (Février 2010) 

Public ISBD [article]  in Signal processing. Image communication > Vol. 25 N° 2 (02 EX.) (Février 2010) . - pp. 94-110 Titre : Flexible distribution of complexity by hybrid predictive-distributed video coding Type de document : texte imprimé Auteurs : Jürgen Slowack, Auteur ; Jozef Škorupa, Auteur ; Stefaan Mys, Auteur Année de publication : 2010 Article en page(s) : pp. 94-110 Note générale : Electronique Langues : Anglais (eng) Mots-clés : Distributed  video  coding  Hybrid  video  coding  Wyner-Ziv  coding Index. décimale : 621.382 Dispositifs électroniques utilisant les effets des corps solides. Dispositifs semi-conducteurs Résumé : There is currently limited flexibility for distributing complexity in a video coding system. While rate-distortion-complexity (RDC) optimization techniques have been proposed for conventional predictive video coding with encoder-side motion estimation, they fail to offer true flexible distribution of complexity between encoder and decoder since the encoder is assumed to have always more computational resources available than the decoder. On the other hand, distributed video coding solutions with decoder-side motion estimation have been proposed, but hardly any RDC optimized systems have been developed. To offer more flexibility for video applications involving multi-tasking or battery-constrained devices, in this paper, we propose a codec combining predictive video coding concepts and techniques from distributed video coding and show the flexibility of this method in distributing complexity. We propose several modes to code frames, and provide complexity analysis illustrating encoder and decoder computational complexity for each mode. Rate distortion results for each mode indicate that the coding efficiency is similar. We describe a method to choose which mode to use for coding each inter frame, taking into account encoder and decoder complexity constraints, and illustrate how complexity is distributed more flexibly. DEWEY : 361.382 ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235640%23 [...] [article] Flexible distribution of complexity by hybrid predictive-distributed video coding [texte imprimé] / Jürgen Slowack, Auteur ; Jozef Škorupa, Auteur ; Stefaan Mys, Auteur . - 2010 . - pp. 94-110. Electronique Langues : Anglais (eng) in Signal processing. Image communication > Vol. 25 N° 2 (02 EX.) (Février 2010) . - pp. 94-110 Mots-clés : Distributed  video  coding  Hybrid  video  coding  Wyner-Ziv  coding Index. décimale : 621.382 Dispositifs électroniques utilisant les effets des corps solides. Dispositifs semi-conducteurs Résumé : There is currently limited flexibility for distributing complexity in a video coding system. While rate-distortion-complexity (RDC) optimization techniques have been proposed for conventional predictive video coding with encoder-side motion estimation, they fail to offer true flexible distribution of complexity between encoder and decoder since the encoder is assumed to have always more computational resources available than the decoder. On the other hand, distributed video coding solutions with decoder-side motion estimation have been proposed, but hardly any RDC optimized systems have been developed. To offer more flexibility for video applications involving multi-tasking or battery-constrained devices, in this paper, we propose a codec combining predictive video coding concepts and techniques from distributed video coding and show the flexibility of this method in distributing complexity. We propose several modes to code frames, and provide complexity analysis illustrating encoder and decoder computational complexity for each mode. Rate distortion results for each mode indicate that the coding efficiency is similar. We describe a method to choose which mode to use for coding each inter frame, taking into account encoder and decoder complexity constraints, and illustrate how complexity is distributed more flexibly. DEWEY : 361.382 ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235640%23 [...]

Introducing skip mode in distributed video coding / Stefaan Mys in Signal processing. Image communication, Vol. 24 N° 3 (Mars 2009) 

Public ISBD [article]  in Signal processing. Image communication > Vol. 24 N° 3 (Mars 2009) . - pp. 200-213 Titre : Introducing skip mode in distributed video coding Type de document : texte imprimé Auteurs : Stefaan Mys, Auteur ; Jürgen Slowack, Auteur ; Jozef Škorupa, Auteur Article en page(s) : pp. 200-213 Note générale : Electronique Langues : Anglais (eng) Mots-clés : Distributed  video  coding  Wyner–Ziv  coding  Skip  mode  Coding  efficiency Index. décimale : 621.382 Dispositifs électroniques utilisant les effets des corps solides. Dispositifs semi-conducteurs Résumé : Although it was proven in the 1970s already by Wyner and Ziv and Slepian and Wolf that, under certain conditions, the same rate–distortion boundaries exist for distributed video coding (DVC) systems as for traditional predicting systems, until now no practical DVC system has been developed that even comes close to the performance of state-of-the-art video codecs such as H.264/AVC in terms of rate–distortion. Some important factors for this are the lower accuracy of the motion estimation performed at the decoder, the inaccurate modeling of the correlation between the side information and the original frame, and the absence in most state-of-the-art DVC systems of anything conceptually similar to the notion of skipped macroblocks in predictive coding systems. This paper proposes an extension of a state-of-the-art transform domain residual DVC system with an implementation of skip mode. The skip mode has an impact at two different places: in the turbo decoder, more specifically the soft input, soft output (SISO) convolutional decoder, and in the puncturing of the parity bits. Results show average bitrate gains up to 39% (depending on the sequence) achieved by combining both approaches. Furthermore, a hybrid video codec is presented where the motion estimation task is shifted back to the encoder. This results in a drastic increase in encoder complexity, but also in a drastic performance gain in terms of rate–distortion, with average bitrate savings up to 60% relative to the distributed video codec. In the hybrid video codec, smaller but still important average bitrate gains are achieved by implementing skip mode: up to 24%. DEWEY : 361.382 ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235640%23 [...] [article] Introducing skip mode in distributed video coding [texte imprimé] / Stefaan Mys, Auteur ; Jürgen Slowack, Auteur ; Jozef Škorupa, Auteur . - pp. 200-213. Electronique Langues : Anglais (eng) in Signal processing. Image communication > Vol. 24 N° 3 (Mars 2009) . - pp. 200-213 Mots-clés : Distributed  video  coding  Wyner–Ziv  coding  Skip  mode  Coding  efficiency Index. décimale : 621.382 Dispositifs électroniques utilisant les effets des corps solides. Dispositifs semi-conducteurs Résumé : Although it was proven in the 1970s already by Wyner and Ziv and Slepian and Wolf that, under certain conditions, the same rate–distortion boundaries exist for distributed video coding (DVC) systems as for traditional predicting systems, until now no practical DVC system has been developed that even comes close to the performance of state-of-the-art video codecs such as H.264/AVC in terms of rate–distortion. Some important factors for this are the lower accuracy of the motion estimation performed at the decoder, the inaccurate modeling of the correlation between the side information and the original frame, and the absence in most state-of-the-art DVC systems of anything conceptually similar to the notion of skipped macroblocks in predictive coding systems. This paper proposes an extension of a state-of-the-art transform domain residual DVC system with an implementation of skip mode. The skip mode has an impact at two different places: in the turbo decoder, more specifically the soft input, soft output (SISO) convolutional decoder, and in the puncturing of the parity bits. Results show average bitrate gains up to 39% (depending on the sequence) achieved by combining both approaches. Furthermore, a hybrid video codec is presented where the motion estimation task is shifted back to the encoder. This results in a drastic increase in encoder complexity, but also in a drastic performance gain in terms of rate–distortion, with average bitrate savings up to 60% relative to the distributed video codec. In the hybrid video codec, smaller but still important average bitrate gains are achieved by implementing skip mode: up to 24%. DEWEY : 361.382 ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235640%23 [...]

Rate-distortion driven decoder-side bitplane mode decision for distributed video coding / Jürgen Slowack in Signal processing. Image communication, Vol. 25 N° 9 (Octobre 2010) 

Public ISBD [article]  in Signal processing. Image communication > Vol. 25 N° 9 (Octobre 2010) . - pp. 660–673 Titre : Rate-distortion driven decoder-side bitplane mode decision for distributed video coding Type de document : texte imprimé Auteurs : Jürgen Slowack, Auteur ; Stefaan Mys, Auteur ; Jozef Škorupa, Auteur Année de publication : 2012 Article en page(s) : pp. 660–673 Note générale : Electronique Langues : Anglais (eng) Mots-clés : Distributed  video  coding  Mode  decision  Wyner–Ziv  coding Résumé : Distributed video coding (DVC) features simple encoders but complex decoders, which lies in contrast to conventional video compression solutions such as H.264/AVC. This shift in complexity is realized by performing motion estimation at the decoder side instead of at the encoder, which brings a number of problems that need to be dealt with. One of these problems is that, while employing different coding modes yields significant coding gains in classical video compression systems, it is still difficult to fully exploit this in DVC without increasing the complexity at the encoder side. Therefore, in this paper, instead of using an encoder-side approach, techniques for decoder-side mode decision are proposed. A rate-distortion model is derived that takes into account the position of the side information in the quantization bin. This model is then used to perform mode decision at the coefficient level and bitplane level. Average rate gains of 13–28% over the state-of-the-art DISCOVER codec are reported, for a GOP of size four, for several test sequences. ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science/article/pii/S0923596510000767 [article] Rate-distortion driven decoder-side bitplane mode decision for distributed video coding [texte imprimé] / Jürgen Slowack, Auteur ; Stefaan Mys, Auteur ; Jozef Škorupa, Auteur . - 2012 . - pp. 660–673. Electronique Langues : Anglais (eng) in Signal processing. Image communication > Vol. 25 N° 9 (Octobre 2010) . - pp. 660–673 Mots-clés : Distributed  video  coding  Mode  decision  Wyner–Ziv  coding Résumé : Distributed video coding (DVC) features simple encoders but complex decoders, which lies in contrast to conventional video compression solutions such as H.264/AVC. This shift in complexity is realized by performing motion estimation at the decoder side instead of at the encoder, which brings a number of problems that need to be dealt with. One of these problems is that, while employing different coding modes yields significant coding gains in classical video compression systems, it is still difficult to fully exploit this in DVC without increasing the complexity at the encoder side. Therefore, in this paper, instead of using an encoder-side approach, techniques for decoder-side mode decision are proposed. A rate-distortion model is derived that takes into account the position of the side information in the quantization bin. This model is then used to perform mode decision at the coefficient level and bitplane level. Average rate gains of 13–28% over the state-of-the-art DISCOVER codec are reported, for a GOP of size four, for several test sequences. ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science/article/pii/S0923596510000767