Codage d'objets de type VOP par représentation en régions auto-extractibles

Le nouveau standard multimédia Mpeg-4 traite aussi bien des aspects compression que de fonctionnalités de haut niveau telles que la manipulation d'objets. Notre approche propose un cadre unique permettant une compression efficace tout en offrant une segmentation à coût « quasi-nul » à travers le principe de représentation en régions auto-extractibles. Aussi montrons-nous ici que notre méthode peut constituer une alternative au mode classique de codage intra de Mpeg-4. En particulier, l'approche réussi à unifier le codage de la forme et de la texture d'un VOP

Color LAR codec : a color image representation and compression scheme based on local resolution adjustment and on self-extracting region representation

This LAR (Locally Adaptive Resolution) color image coding scheme yields to an efficient progressive compression with a better subjective quality than Jpeg2000. Additionally, it offers region functionalities for low bit rate coding and decoding. From highly compressed luminance, a region description, without contours encoding, can be obtained through a segmentation process performed at both coder and decoder. Considering color results, controlled chrominance components segmentation provides a better data consistency simultaneously with a low bit rate compression. As regions and their encoding are based on a same representation grid, enhancement of image quality can be global, or only restricted to a Region Of Interest.Cet article présente un schéma original de codage progressif d'images couleur apportant à la fois une efficacité en termes de compression (meilleure qualité subjective que Jpeg2000) et des fonctionnalités au niveau région à bas débits pour le codeur et le décodeur. À partir de l'image des luminances codée à bas débit par le codec LAR (Locally Adaptive Resolution), une description en régions, sans codage des contours, est obtenue à travers un procédé de segmentation effectué au codeur et au décodeur. Cette segmentation peut être contrôlée par les composantes chromatiques pour une meilleure cohérence du résultat d'un point de vue couleur. Un codage basé régions appliqué sur les images de chrominance produit alors une compression de ces composantes à très bas débit. Comme les régions et le codage de leur contenu partagent une même grille de représentation, l'amélioration de la qualité de l'image peut être globale, ou limitée à une zone d'intérêt

Document image segmentation using a multiresolution approach. Accurate text line extraction

An overall scheme and related algorithms performing accurate text lines extraction from an image of document are described in this paper The type of documents concerned here is very complex, with totally unconstrained data . Postal objects, especially the so-calledfiatobjects, i.e. : large envelopes, magazines, . . . are within this kind of documents. Three main phases have been considered to achieve the overall function . First of all, areas of interest are located using a multiresolution approach allowing to preserve from large variability of text features . This is performed directly on the gray-level image . A binarization stage, taking advantage of the results of the localization, is next performed to extract the lines . At last, a post-segmentation involving the located areas in the gray-level images and structural features extracted from the lines allows to deal with severe cases such as overlapping lines induced by handwritten texts . Examples related to text line extraction on postal objects are illustrating this paper.Cet article présente une méthodologie et des outils de traitement permettant de localiser puis d'extraire précisément les lignes de texte contenues dans l'image d'un document. La classe des documents visés est de type document très complexe, leurs contenus étant totalement non contraints. Globalement la méthodologie s'articule autour de trois étapes clés. La première est une localisation des zones d'intérêt. Elle est réalisée directement sur l'image en niveaux de gris et utilise une approche multirésolution garantissant une grande robustesse vis-à-vis de la très forte variabilité des textes: taille, disposition, présentation. Une étape de binarisation réalisée séparément pour chaque zone d'intérêt permet dans une seconde phase l'extraction proprement dite des lignes de texte. Enfin, une post-segmentation faisant coopérer la localisation initiale et des caractéristiques structurelles extraites de la ligne permet de traiter les cas très perturbants pour la lecture du chevauchement de lignes sur de l'écriture manuscrite. Des exemples relevant de la problématique de l'extraction des lignes du bloc adresse sur objets postaux (grandes lettres, magazines) illustrent cet article

Community-acquired pneumonia by Legionella pneumophila serogroups 1–6 in Brazil

SummaryA prospective cohort study of adult patients hospitalized due to community-acquired pneumonia was carried out for 1 year in a Brazilian university general hospital to detect the incidence of community-acquired pneumonia by Legionella pneumophila serogroups 1–6. During a whole year, a total of 645 consecutive patients who were hospitalized due to a initial presumptive diagnosis of respiratory disease by ICD-10 (J00–J99), excluding upper respiratory diseases, were screened to detect the patients with community-acquired pneumonia. Fifty-nine consecutive patients hospitalized due to community-acquired pneumonia between July 19, 2000 and July 18, 2001, were included in the study. They had determinations of serum antibodies to L. pneumophila serogroups 1–6 by indirect immunofluorescence antibody test at the Infectious Diseases Laboratory of University of Louisville (KY, USA) and urinary antigen tests for L. pneumophila serogroup 1. Three patients had community-acquired pneumonia by L. pneumophila serogroups 1–6, two patients being diagnosed by seroconversion and positive urinary antigen tests; the other had negative serologies but strongly positive urinary antigen test. The incidence of community-acquired pneumonia by L. pneumophila serogroups 1–6 in our hospital was 5.1%

Secretion of Hepatitis C Virus Envelope Glycoproteins Depends on Assembly of Apolipoprotein B Positive Lipoproteins

The density of circulating hepatitis C virus (HCV) particles in the blood of chronically infected patients is very heterogeneous. The very low density of some particles has been attributed to an association of the virus with apolipoprotein B (apoB) positive and triglyceride rich lipoproteins (TRL) likely resulting in hybrid lipoproteins known as lipo-viro-particles (LVP) containing the viral envelope glycoproteins E1 and E2, capsid and viral RNA. The specific infectivity of these particles has been shown to be higher than the infectivity of particles of higher density. The nature of the association of HCV particles with lipoproteins remains elusive and the role of apolipoproteins in the synthesis and assembly of the viral particles is unknown. The human intestinal Caco-2 cell line differentiates in vitro into polarized and apoB secreting cells during asymmetric culture on porous filters. By using this cell culture system, cells stably expressing E1 and E2 secreted the glycoproteins into the basal culture medium after one week of differentiation concomitantly with TRL secretion. Secreted glycoproteins were only detected in apoB containing density fractions. The E1–E2 and apoB containing particles were unique complexes bearing the envelope glycoproteins at their surface since apoB could be co-immunoprecipitated with E2-specific antibodies. Envelope protein secretion was reduced by inhibiting the lipidation of apoB with an inhibitor of the microsomal triglyceride transfer protein. HCV glycoproteins were similarly secreted in association with TRL from the human liver cell line HepG2 but not by Huh-7 and Huh-7.5 hepatoma cells that proved deficient for lipoprotein assembly. These data indicate that HCV envelope glycoproteins have the intrinsic capacity to utilize apoB synthesis and lipoprotein assembly machinery even in the absence of the other HCV proteins. A model for LVP assembly is proposed

Th1 Disabled Function in Response to TLR4 Stimulation of Monocyte-Derived DC from Patients Chronically-Infected by Hepatitis C Virus

Background: Lack of protective antibodies and inefficient cytotoxic responses are characteristics of chronic hepatitis C infection. A defect in dendritic cell (DC) function has thus been suspected, but this remains a controversial issue. Methods and Findings: Here we show that monocyte-derived DC (MoDC) from chronically-infected patients can mature in response to TLR1/2, TLR2/6 or TLR3 ligands. In contrast, when stimulated with the TLR4 ligand LPS, MoDC from patients show a profound defect in inducing IFNc secretion by allogeneic T cells. This defect is not due to defective phenotypic maturation or to the presence of HCV-RNA in DC or monocytes but is correlated to reduced IL-12 secretion by DC. Restoration of DC ability to stimulate IFNc secretion can be obtained by blocking MEK activation in DC, indicating that MEK/ ERK pathway is involved in the Th1 defect of MoDC. Monocytes from HCV patients present increased spontaneous secretion of cytokines and chemokines, especially MIP-1b. Addition of MIP-1b on healthy monocytes during differentiation results in DC that have Th1 defect characteristic of MoDC from HCV patients, suggesting that MIP-1b secretion by HCV monocytes participates in the Th1 defect of DC. Conclusions: Our data indicate that monocytes from HCV patients are activated in vivo. This interferes with their differentiation into DC, leading to deficient TLR4 signaling in these cells that are enable to induce a Th1 response. Thi

Emerging video coding performance: 4K quality monitoring

International audienceThe new coding tools, developed under the Joint Exploration Model (JEM) software, have been proposed with the main goal to explore their potential coding gain in the perspective to develop a new video coding standard. In this paper we present a performance-based comparison between the JEM and HEVC reference software (HM) through a set of subjective quality assessments. Different video sequences, encoded using both JEM and HM software at different bitrates, have been used in this experiment. Results have shown that the JEM codec enables, subjectively, a quality enhancement up to 40% at similar low bit rates. © 2017 IEEE

Audiovisual quality study for videoconferencing on IP networks

International audienc

Enhanced intra prediction modes signalling in HEVC

International audienceThe High Efficiency Video Coding (HEVC) standard defines 35 Intra Prediction Modes (IPM) to provide an efficient compression of intra coded blocks. To signal these IPMs to the decoder a list of 3 Most Probable Modes (MPM) is created based on the IPMs of the neighbour Intra coded blocks. These MPMs will be transmitted in the bit stream with a reduced number of bits. However, the signalling scheme used in HEVC is not optimal and can be further improved. In this paper a method is proposed to enhance the Intra mode signalling in HEVC. The IPM signaling is first modelled as a tree with forks and leaves representing tests and labels, respectively. The proposed solution introduces new decision tree process by adding new tests and new labels not considered in HEVC. This solution provides a systematic way to find the best signalling scheme for a given set of data. Experimental results show that the proposed solution enables to reduce the BD-Rate by 0.38% in all Intra coding configuration. © 2016 IEEE