1,720,960 research outputs found
Real-Time Rough Extraction of Foreground Objects in MPEG1,2 Compressed Video
No full textThis paper describes a new approach to extract foreground objects in MPEG1,2 video streams, in the framework of “rough indexing paradigm”, that is starting from rough data obtained by only partially decoding the compressed stream. In this approach we use both P-frame motion information and I-frame colour information to identify and extract foreground objects. The particularity of our approach with regards to the state of the art methods consists in a robust estimation of camera motion and its use for localisation of real objects and filtering of parasite zones.
Secondly, a spatio-temporal filtering of roughly segmented objects at DC resolution is fulfilled using motion trajectory and gaussian-like shape characteristic function. This paradigm results in content description in real time, maintaining a good level of details
Opacity modulation for interactive volume rendering of medical images
No full textInteractivity is a main requirement for 3D visualisation of medical images in a variety of clinical applications. The good matching between segmentation and rendering techniques is essential to design easy to use interactive systems which assist the physicians in dynamically creating and manipulating "diagnostically relevant" images from the volumetric data sets. In this work we consider the above problem within an original interactive visualisation paradigm. By this paradigm we want to highlight the twofold clinical requirement of a) detecting and visualising the structures of diagnostic interest (SoDI's) and b) adding to the 3D scene some other structures to create a meaningful visual context. Being the opacity modulation of the different structures a crucial point, we propose an opacity management which reflects the paradigm ideas and operates by means of a twofold indexed look-up table (2iLUT). the 2iLUT consists of a combination of attribute based and object based opacity management and is here designed and experimented in order to combine the time interaction benefits of an indexed opacity setting with the effective handling of the above classification and visualisation clinical requirements
Performance evaluation of wavelet-based HD video coding
No full textThis paper is intended as a complement of document n3954 and presents some preliminary evaluation of coding efficiency of a scalable wavelet-based encoder. Two HD video sequences have been encoded according to test conditions derived from those used to evaluate the coding efficiency of JSVM and VidWav[4]. Assuming that exploiting temporal redundancy in video coding improves compression efficiency, the aim of this work is to further investigate advantage and disadvantage of applying a motion compensated temporal filtering, in term of compression gain, with respect to pure intra coding
Wavelet-based encoding for HD applications
No full textIn the past decades, most of the research on image and video compression has focused on addressing high bandwidth- constrained environments. However, for high resolution and high quality image and video compression, as in the case of High Definition Television (HDTV) or Digital Cinema (DC), the primary constraints are related to quality and flexibility. This paper presents a comparison between scalable wavelet-based video codecs and the state of the art in single point encoding and it investigates the obtainable compression efficiency when using temporal correlation with respect to pure intra coding
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Multiple Moving Object Detection for Fast Video Content Description in Compressed Domain
No full textIndexing deals with the automatic extraction of information with the objective of automatically describing and organizing the content. Thinking of a video stream, different types of information can be considered semantically important. Since we can assume that the most relevant one is linked to the presence of moving foreground objects, their number, their shape, and their appearance can constitute a good mean for content description. For this reason, we propose to combine both motion information and region-based color segmentation to extract moving objects from an MPEG2 compressed video stream starting only considering low-resolution data. This approach, which we refer to as “rough indexing,†consists in processing P-frame motion information first, and then in performing I-frame color segmentation. Next, since many details can be lost due to the low-resolution data, to improve the object detection results, a novel spatiotemporal filtering has been developed which is constituted by a quadric surface modeling the object trace along time. This method enables to effectively correct possible former detection errors without heavily increasing the computational effort
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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