Publications - Xavier Delaunay

Abstract : This paper proposes a complete compression and coding scheme for on-board satellite applications considering the main on-board constraints: low computational power and easy bit-rate control. The proposed coding scheme improves the performance of the current CCSDS recommendation (Consultative Committee for Space Data Systems) for a low additional complexity. We consider post-transforms in the wavelet domain, select the best representation for each block of wavelet coefficients, and encode it into an embedded bit stream. After applying a classical wavelet transform of the image, several concurrent representations of blocks of wavelet coefficients are generated. The best representations are then selected according to a rate-distortion criterion. Finally, a specific bit-plane encoder derived from the CCSDS recommendation produces an embedded bit stream ensuring the easy rate control required. In this article, both the post-transforms and the best representation selection have been adapted to the low complexity constraint and the CCSDS coder has been modified to compress post-transformed representations.

BibTeX :
@article {springerlink:10.1007/s12243-011-0252-0,
   author = {Delaunay, Xavier and Chabert, Marie and Charvillat, Vincent and Morin, Géraldine},
   affiliation = {NOVELTIS, Parc technologique du canal, 2 av. de l’Europe, 31520 Ramonville-Saint-Agne, France},
   title = {Satellite image compression by concurrent representations of wavelet blocks},
   journal = {Annals of Telecommunications},
   publisher = {Springer Paris},
   issn = {0003-4347},
   keyword = {Engineering},
   pages = {71-80},
   volume = {67},
   issue = {1},
   url = {http://dx.doi.org/10.1007/s12243-011-0252-0},
   note = {10.1007/s12243-011-0252-0},
   year = {2012}
}
Copyright © 2011, Institut Télécom and Springer-Verlag.
Abstract : This paper proposes a selective compression scheme to enhance the quality of regions of interest and to avoid wasting coding resources on irrelevant parts of satellite images. Although 80\% of SPOT 5 images contain clouds, the information about clouds is irrelevant since the main mission of this satellite, like many other optical Earth observation satellite, is Earth ground observation. However in current on-board compression algorithms pixels of clouds are processed as any other pixels of the image and are transmitted with the same quality and bit-rate. This results in a waste of data rate which could have been used either to enhance the quality of the relevant part of the transmitted image (thanks to progressive coding) or to transmit more images. The goal of selective image coding is to avoid this waste by on-board cloud detection [1] and region of interest (ROI) coding techniques. This paper focuses on this second point: the implementation of ROI coding techniques in an algorithm derived of the CCSDS 122 recommendation [2].
Two ROI coding methods have been integrated to the algorithm: the maxshift and the scaling methods. Both respect the constraint of progressive coding and fine region delineation. Both also allow multiple levels of interest, that is, several ROI with different levels of interest and a background region. After the wavelet transform, the maxshift method operates by up-shifting all the ROI bitplanes above the most significant bitplane of the background region. Scaling operates by multiplying the ROI wavelet coefficients by a scaling factor or by up-shifting the ROI bitplanes by an number of shifts equivalent to this scaling factor, not necessarily greater the most significant bitplane. As the coding process stops before it reaches the least significant bitplane, up-shifted ROI wavelet coefficients are coded with greater accuracy than the background coefficients. As a result, ROI are transmitted with better quality than the background region.
First, we shall motivate the choice of the maxshift and scaling methods. Then, both methods will be detailed. The implemented algorithm does not comply with the CCSDS 122 recommendation. Thus, in the next section, the modifications required to add ROI coding features to the algorithm will be developed. Finally, the proposed scheme will be evaluated by comparing rate-distortion curves obtained by the compression of several Quickbird images with the ROI methods and the original CCSDS 122 coder.

[1] C. Thiebaut, P. Dejean, P. Fillatreau, A. Speciel and C. Latry, "On-Board Cloud Detection for Selective Compression of High-Resolution Images," On-Board Payload Data Compression Workshop, OBPDC 2008.

[2] P-S. Yeh et al., "The New CCSDS Image Compression Recommendation," in proc. of the IEEE Aerospace Conference, pp. 1–8, Big Sky, MT, March 5–12, 2005.

BibTeX :
@inproceedings{delaunay:obpdc10,
  author = {Xavier Delaunay and Carole Thiebaut and Marie Chabert and Vincent
	Charvillat and Géraldine Morin},
  title = {Progressive Coding of Satellite Images with Regions of Interest},
  booktitle = {On-Board Payload Data Compression Workshop},
  year = {2010},
  address = {Toulouse, France},
  month = oct,
  url = {http://www.congrex.nl/10c19/}
}
Abstract : This paper proposes a novel compression scheme with a tunable complexity-rate-distortion trade-off. As images increase in size and resolution, more efficient compression schemes with low complexity are required on-board Earth observation satellites. The standard of the Consultative Committee for Space Data Systems (CCSDS) defines a strip-based compression scheme with the advantages of a low complexity and an easy rate control [CCSDS, Image Data Compression Recommended Standard CCSDS 122.0-B-1 Blue Book, November 2005]. However, future mission specifications expect higher performance in terms of rate-distortion. The scheme proposed in this paper intends to perform better than the CCSDS standard while preserving low complexity and easy rate control. Moreover, to comply with existing on-board devices, the proposed core compression engine still uses the wavelet transform but in association with a linear post-processing inspired from the bandelet transform. The post-transform decomposes a small block of wavelet coefficients on a particular basis. This basis is adaptively selected within a predefined dictionary by rate-distortion optimization. The computational complexity depends upon the dictionary size and of the basis structure. An extremely simple dictionary, reduced to the Hadamard basis, is proposed. The post-transform efficiency is illustrated by experiments on various Earth observation images provided by the French Space Agency (CNES).

BibTeX :
@article{delaunay:sigpro09,
  author = {Xavier Delaunay and Marie Chabert and Vincent Charvillat and Géraldine Morin},
  title = {Satellite Image Compression by Post-Transforms in the Wavelet Domain},
  journal = {Elsevier Signal Processing},
  year = {2010},
  volume = {90},
  number = {2},
  pages = {599--610},
  doi = {http://dx.doi.org/10.1016/j.sigpro.2009.07.024}
}

Copyright © 2009 Elsevier B.V. All rights reserved.
Abstract : Les post-transformées permettent d’exploiter des dépendances linéaires entre coefficients d’ondelettes voisins. Dans ce papier, le schéma de compression par posttransformée est modifié afin d’être adapté à une compression progressive. De plus, prenant en considération les contraintes d’un algorithme de compression à bord d’un satellite, la complexité calculatoire de cette méthode est réduite au minimum. Le codeur par plans de bits du CCSDS est ensuite modifié afin de pouvoir coder la posttransformée. Ainsi, les avantages de la post-transformée et du codeur du CCSDS sont combinés. Cela permet d’améliorer les résultats en compression.

BibTeX :
@inproceedings{delaunay:coresa09,
  author = {Xavier Delaunay and Carole Thiebaut and Marie Chabert and Géraldine Morin},
  title = {Codage progressif de post-transformées par le codeur du {CCSDS}},
  booktitle = {CORESA'09},
  publisher = {France Telecom R\&D},
  year = {2009},
  url = {http://coresa2009.enseeiht.fr/}
}
Abstract : This paper deals with satellite image compression based on a post-processing of the wavelet transform of images. The bandelet transform is a directional post-processing of wavelet coefficients. Thanks to a low computational complexity, this transform is a good candidate for future on-board satellite image compression systems. This paper first analyzes the ability of the bandelets to exploit directional correlations between wavelet coefficients. This study leads to an improved post-processing with a better decorrelation of adjacent wavelet coefficients in the vertical or in the horizontal direction taking into account the wavelet subband orientations. To perform even better decorrelation, bases are also learned by PCA. This results in an improved compression performance without increasing the computational complexity.

BibTeX :
@inproceedings{delaunay:icassp08,
  author = {Xavier Delaunay and Marie Chabert and Vincent Charvillat and Géraldine Morin and Rosario Ruiloba},
  title = {Satellite image compression by directional decorrelation of wavelet coefficients},
  booktitle = {ICASSP'08},
  publisher = {IEEE},
  year = {2008},
  pages = {1193--1196},
  doi = {http://dx.doi.org/10.1109/ICASSP.2008.4517829}
}

Copyright 2008 IEEE. Published in the IEEE 2008 International Conference on Acoustics, Speech, and Signal Processing (ICASSP 2008), scheduled for March 30 - April 4, 2008 in Las Vegas, Nevada, U.S.A. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works, must be obtained from the IEEE. Contact: Manager, Copyrights and Permissions / IEEE Service Center / 445 Hoes Lane / P.O. Box 1331 / Piscataway, NJ 08855-1331, USA. Telephone: + Intl. 908-562-3966.
Abstract : Current state-of-the-art on-board image compression systems are based on the wavelet transform. However, redundancies can still be found between the wavelet coefficients. To exploit these remaining redundancies and increase the compression efficiency, the new post-transform compression scheme applies a second transform on blocks of coefficients. This paper proposes to adapt the post-transform process to on-board constraints using the low complexity Hadamard post-transform and describes how it can be efficiently included in the bit-plane encoder of the CCSDS (Consultative Committee for Space Data Systems) recommendation. Compression performance is provided for each adjustment made to the post-transform process.

BibTeX :
@inproceedings{delaunay:obpdc08,
  author = {Xavier Delaunay and Carole Thiebaut and Emmanuel Christophe and Rosario Ruiloba and Marie Chabert and Vincent Charvillat and Géraldine Morin},
  title = {Lossy compression by post-transforms in the wavelet domain},
  booktitle = {On-Board Payload Data Compression Workshop},
  year = {2008},
  url = {http://www.congrex.nl/08c20/}
}
Abstract : Future high resolution instruments planned by CNES for space remote sensing missions will lead to higher bit rates because of the increase in resolution and dynamic range. For example, the ground resolution improvement induces a data rate multi-plied by 8 from SPOT4 to SPOT5 and by 28 to PLEIADES-HR. Lossy data compression with low complexity algorithms is then needed since compression ratio are always higher. New image compression algorithms have been used to increase their compression performance while complying with image quality requirements from the community of users and experts. Thus, DPCM algorithm used on-board SPOT4 was replaced by a DCT-based compressor on-board SPOT5. Recent compression algorithms such as PLEIADES-HR one use a wavelet-transform and a bit-plane encoder. But future compressors will have to be more powerful to reach higher compression ratios. New transforms are studied by CNES to exceed the DWT but a per-formance gap could be obtained with selective compression. This article gives an overview of CNES past and present studies of on-board compression algorithms for high-resolution images.

BibTeX :
@inproceedings{thiebaut:spie08,
  author = {Carole Thiebaut and Xavier Delaunay and Christophe Latry and Gilles Moury},
  title = {{CNES} studies for on-board compression of high-resolution satellite images},
  booktitle = {Satellite Data Compression, Communication, and Processing IV},
  publisher = {SPIE},
  year = {2008},
  pages = {70840F.1--70840F.8},
  doi = {http://dx.doi.org/10.1117/12.798121}
}
Abstract : This paper deals with the optimization of a new technique of image compression. After the wavelet transform of an image, blocks of coefficients are further linearly decomposed using a basis selected in a dictionary. This dictionary is known by both the encoder and the decoder. This approach is a generalization of the bandelet transform. This paper investigates the problem of the best basis selection. On each block of wavelet coefficients, this selection is made by minimization of a Lagrangian rate-distortion criterion. Theoretical expressions of the optimal Lagrangian multiplier can be computed based on asymptotic hypotheses. A nearly exhaustive search of the optimal Lagrangian multiplier is done for the compression of high resolution satellite images. This numerical study validates the asymptotic theoretical expressions but as well provides a refined expression of the Lagrangian multiplier. At last, the compression results obtained using those different expressions are compared to the optimal compression results obtained with the exhaustive search.

BibTeX :
@inproceedings{delaunay:icip08,
  author = {Xavier Delaunay and Emmanuel Christophe and Carole Thiebaut and Vincent Charvillat},
  title = {Best post-transforms selection in a rate distortion sense},
  booktitle = {ICIP'08},
  publisher = {IEEE},
  year = {2008},
  pages = {2896--2899},
  doi = {http://dx.doi.org/10.1109/ICIP.2008.4712400}
}

Copyright 2008 IEEE. Published in the IEEE 2008 International Conference on Image Processing (ICIP 2008), scheduled for October 12-15, 2008 in San Diego, California, U.S.A. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works, must be obtained from the IEEE. Contact: Manager, Copyrights and Permissions / IEEE Service Center / 445 Hoes Lane / P.O. Box 1331 / Piscataway, NJ 08855-1331, USA. Telephone: + Intl. 908-562-3966.
Abstract : Le CNES s'intéresse aux nouvelles transformées pour accroître les performances de la compression d'images à bord des satellites d'observation de la Terre. Dans cette thèse nous étudions les post-transformées. Elles sont appliquées après la transformée en ondelettes. Chaque bloc de coefficients d'ondelettes est de nouveau transformé dans une base sélectionnée dans un dictionnaire par minimisation d'un critère débit-distorsion. Nous commençons par mettre en évidence des dépendances entre coefficients d'ondelettes qui limitent les performances en compression. Nous étudions ensuite la transformée en bandelettes par blocs, qui est à l'origine des post-transformées, et nous en optimisons les paramètres pour la compression d'images satellite. En particulier nous adaptons la méthode d'optimisation de Shoham et Gersho à la sélection de la meilleure base de bandelettes. Nous en déduisons une formule du multiplicateur de Lagrange optimal qui intervient dans le critère de sélection. Dans un deuxième temps, nous analysons les dépendances entre coefficients d'ondelettes qui ne sont pas prises en comptes par les bandelettes et nous définissons de nouvelles bases de post-transformées. Les bases construites par ACP minimisent les corrélations entre coefficients post-transformés et compactent l'énergie de chaque bloc sur un petit nombre de coefficients. Cette propriété est exploitée lors du codage entropique. Enfin, nous modifions le critère de sélection des bases pour adapter la post-transformée à une compression progressive. Nous employons alors la post-transformée de Hadamard dans le codeur du CCSDS le tout ayant une faible complexité calculatoire.

BibTeX :
@phdthesis{delaunay:thesis08,
  author = {Xavier Delaunay},
  title = {Compression d'images satellite par post-transformées dans le domaine ondelettes},
  school = {Institut National Polytechnique de Toulouse},
  year = {2008},
  url = {http://ethesis.inp-toulouse.fr/archive/00000693/}
}
Abstract : This paper studies the performance of the ZC contexts in JPEG2000. A quality criterion based on the mutual information is introduced. According to this criterion, there exist ZC contexts which are not effective in any bit-plane. They can thus be merged with others without significant loss of the compression efficiency. Since the contextual conditional probabilities strongly depend on the bit-planes, an adaptation of the contexts to the bit-planes is also proposed. First, an optimal context quantizer is used on each bit-planes, then a simple greedy entropy minimization procedure allows to combine the ZC contexts in JPEG2000. The results are compared with a global combination of JPEG2000 ZC contexts. Tests have been performed on a real satellite image data base. With only four ZC contexts, the PSNR is less than 0.01 dB lower than the PSNR with the nine ZC contexts.

BibTeX :
@inproceedings{delaunay:icassp07,
  author = {Xavier Delaunay and Marie Chabert and Géraldine Morin and Vincent Charvillat},
  title = {Bit-plane analysis and contexts combining of {JPEG2000} contexts for on-board satellite image compression},
  booktitle = {ICASSP'07},
  publisher = {IEEE},
  year = {2007},
  pages = {1057--1060},
  doi = {http://dx.doi.org/10.1109/ICASSP.2007.366093}
}

Copyright 2007 IEEE. Published in the IEEE 2007 International Conference on Acoustics, Speech, and Signal Processing (ICASSP 2007), scheduled for April 16-20, 2007 in Honolulu, Hawaii. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works, must be obtained from the IEEE. Contact: Manager, Copyrights and Permissions / IEEE Service Center / 445 Hoes Lane / P.O. Box 1331 / Piscataway, NJ 08855-1331, USA. Telephone: + Intl. 908-562-3966.
Abstract : Cet article s’intéresse à la compression d’images satellite. La technique proposée met en oeuvre la transformée en ondelettes couplée à une post-transformée par blocs sélectionnée dans un dictionnaire de bases. L’originalité du travail réside dans le dictionnaire utilisé. Ce dictionnaire est constitué de bases construites à partir de l’Analyse en Composantes Principales (ACP) sur une base d’apprentissage de blocs de coefficients d’ondelettes. La post-transformée proposée permet d’éliminer les corrélations entre coefficients d’ondelettes voisins. Elle bénéficie aussi de la propriété de concentration d’énergie de l’ACP qui est exploitée au moment du codage.

BibTeX :
@inproceedings{delaunay:gretsi07,
  author = {Xavier Delaunay and Marie Chabert and Géraldine Morin and Carole Thiebaut},
  title = {Post-transformée dans le domaine ondelettes appliquée à la compression d'images satellite},
  booktitle = {GRETSI'07},
  publisher = {CNRS},
  year = {2007},
  pages = {1185--1188},
  url = {http://hdl.handle.net/2042/17721}
}
Abstract : La résolution des images acquises à bord des satellites d’observation de la terre est de plus en plus grande et la compression à bord doit donc être de plus en plus performante pour transmettre les données au sol. L’augmentation des capacités de calcul et de mémoire permet la mise en place d’algorithmes de plus en plus complexes. Actuellement, on envisage des compresseurs capables de compenser les faiblesses de la transformée en ondelettes séparable, et qui utiliseraient une autre transformée et/ou des codeurs plus performants. Dans cette communication, nous mettons en évidence deux sortes de corrélations résiduelles entre coefficients d’ondelettes qu’il serait souhaitable d’éliminer pour améliorer la compression. Les premières corrélations sont situées dans un voisinage local. Les secondes sont liées aux structures géométriques de l’image et sont observées sur de plus grandes distances.

BibTeX :
@inproceedings{delaunay:coresa06,
  author = {Xavier Delaunay and Carole Thiebaut and Vincent Charvillat},
  title = {Compression embarquée d'images satellites : vers l'exploitation de la géométrie},
  booktitle = {CORESA'06},
  publisher = {France Telecom R\&D},
  year = {2006},
  pages = {12--17},
  url = {http://www.stlo.unicaen.fr/coresa2006/}
}