Network


Latest external collaboration on country level. Dive into details by clicking on the dots.

Hotspot


Dive into the research topics where Juan María Sánchez is active.

Publication


Featured researches published by Juan María Sánchez.


Lecture Notes in Computer Science | 1999

Local Color Analysis for Scene Break Detection Applied to TV Commercials Recognition

Juan María Sánchez; Xavier Binefa; Jordi Vitrià; Petia Radeva

TV commercials recognition is a need for advertisers in order to check the fulfillment of their contracts with TV stations. In this paper we present an approach to this problem based on compacting a representative frame of each shot by a PCA of its color histogram. We also present a new algorithm for scene break detection based on the analysis of local color variations in consecutive frames of some specific regions of the image.


Multimedia Tools and Applications | 2002

Shot Partitioning Based Recognition of TV Commercials

Juan María Sánchez; Xavier Binefa; Jordi Vitrià

Digital video applications exploit the intrinsic structure of video sequences. In order to obtain and represent this structure for video annotation and indexing tasks, the main initial step is automatic shot partitioning. This paper analyzes the problem of automatic TV commercials recognition, and a new algorithm for scene break detection is then introduced. The structure of each commercial is represented by the set of its key-frames, which are automatically extracted from the video stream. The particular characteristics of commercials make commonly used shot boundary detection techniques obtain worse results than with other video content domains. These techniques are based on individual image features or visual cues, which show significant performance lacks when they are applied to complex video content domains like commercials. We present a new scene break detection algorithm based on the combined analysis of edge and color features. Local motion estimation is applied to each edge in a frame, and the continuity of the color around them is then checked in the following frame. By separately considering both sides of each edge, we rely on the continuous presence of the objects and/or the background of the scene during each shot. Experimental results show that this approach outperforms single feature algorithms in terms of precision and recall.


international conference on pattern recognition | 2000

Chromatic aberration and depth extraction

Josep Garcia; Juan María Sánchez; Xavier Orriols; Xavier Binefa

We introduce chromatic aberration as a source of visual information that can be useful for autofocus and depth estimation. A color video camera equipped with a lens with chromatic aberration has been used to take images of both step and occlusion edges at several distances from the camera. The defocus measures obtained in the three different RGB color channels of each image are different. We suggest the way this information can be exploited in order to design an autofocus sensor, and also how depth information can be derived.


international conference on multimedia computing and systems | 1999

AudiCom: a video analysis system for auditing commercial broadcasts

Juan María Sánchez; Xavier Binefa

Commercials are very important in TV broadcasts. Many enterprises invest large amounts of money in TV publicity and governments dictate pertinent regulations to preserve consumers rights. AudiCom is a system that detects the broadcast of previously learned commercials and collects some interesting information about them. It is based on a new scene break detection operator that relies on the colors around the edges of the frames, and on the compaction of the information contained in the different shots that constitute the commercials. This compaction is obtained using principal component analysis (PCA) of the color histogram of a representative frame of every shot.


Journal of Visual Languages and Computing | 2000

Linking Visual Cues and Semantic Terms Under Specific Digital Video Domains

Juan María Sánchez; Xavier Binefa; Jordi Vitrià; Petia Radeva

Summary of the feelings related to colorsColor Feelings evoked in the viewerRed Happiness, dynamism, agressiveness, violence, powerOrange Glory, solemnity, vanity, progressGolden yellow Richness, prosperity, happinessDark yellow Deception, cautionGreen Calm, relax, hopeBlue Gentleness, fairness, faithfulness, virtuePurple Melancholy, fearBrown Relax (mostly used as background color) performs an action, communicates dynamism and stirring, while still takes meanquietness, calm and relax. The slope of the scene is also considered. Slanted slopescommunicateaction,butalso happinessandtheywanttoevokeadegreeof unrealityinthescene,whilehorizontalandverticalslopescommunicatecalm.Itisalsointerestingtonotethatslopesinthescenecanbe usedasanheuristicto determineif it hasbeenshotin a man-made scenery,where a dominant slope is found, mainly horizontal or vertical,or in a natural one, where there is not any dominant slope.Edit rhythm is also directly related to the amount of action and dynamism that theadvertiser wants to communicate to the viewers. A video edited using few long shotsandgradualtransitionsinspiresquietness,whilevideoswithmanyshortshotsusingcutsemphasize dynamism and happiness.


international conference on pattern recognition | 2002

Coupled Markov chains for video contents characterization

Juan María Sánchez; Xavier Binefa; John R. Kender

We propose a compact descriptor of video contents based on modeling the temporal behavior of image features using coupled Markov chains. The framework allows us to combine multiple features within the same model, including the representation of the dependencies and relationships between them. The Kullback-Leibler divergence stands out as the base of a perceptually significant distance measure for our descriptor Our experiments show that complex highlevel visual contents in different domains can be characterized using very simple low-level features, such as motion and color.


international conference on pattern recognition | 2000

Color normalization for appearance based recognition of video key-frames

Juan María Sánchez; Xavier Binefa

Colour image variations produced by the change of video acquisition devices strongly affect colour appearance based recognition tasks in digital video applications. Up to date, many algorithms have been developed in order to achieve independence from different image formation factors like intensity, orientation and colour of the illumination source. We check the capability of three of these approaches to generate device independent colour representations in order to be used as a normalization step previous to the recognition process. Our previously developed color correction approach for video imagery based on Gaussian mixture models has also been tested. Experimental results show that a simple algorithm like the grayworld correction is enough for appearance based recognition under this particular kind of color variability. Similar recognition rates are obtained using our correction, with the advantage that the visual quality of normalized images is preserved. In digital video library applications, where not only recognition tasks are performed, this approach becomes much more useful.


iberian conference on pattern recognition and image analysis | 2003

Shot Segmentation Using a~Coupled Markov Chains Representation of Video Contents

Juan María Sánchez; Xavier Binefa

We present a shot segmentation method based on the representation of visual contents in video using a coupled Markov chains approach. This representation allows us to combine different image features and to keep information about all the images since the beginning of the shot, instead of simply comparing adjacent frames. We also define an adaptative detection threshold that depends on the distance measures that are obtained, instead of trying to find a fixed threshold. Results show that the combination of color and motion image features in the same representation provides a more robust detection of shot boundaries than using each feature separately.


Lecture Notes in Computer Science | 2000

Color Normalization for Digital Video Processing

Juan María Sánchez; Xavier Binefa

The color appearance of digital video imagery acquired from analog sources is affected by intrinsic device imperfections. Although the human visual system (HVS) is capable of perceiving color variations when comparing different acquisitions of the same video, it is able to identify the colors in an isolated image as well. Color based computer vision processes applied within digital video libraries do not have this capability and their performance is severely reduced. This paper presents a method for modeling the intrinsic color appearance given by acquisition devices. It is based on the approximation of the distribution of colors generated by a device using a mixture of Gaussians in RGB space. Its parameters are encoded in a specifically designed pattern, which provides a dense estimation of the distribution of colors along the whole RGB space. In this way, the model can be attached to every acquired video in order to put its original color appearance on record. The approximation by mixtures of Gaussians lets us define transformations between them that preserve the identity of colors. This fact is shown in the case of skin color segmentation, where the underlying concept of color is captured from samples obtained by a particular device. Other applications of color correction in digital video are pointed out in this paper as well.


Stroke | 2017

Benefits of Emergency Departments’ Contribution to Stroke Prophylaxis in Atrial Fibrillation: The EMERG-AF Study (Emergency Department Stroke Prophylaxis and Guidelines Implementation in Atrial Fibrillation)

Blanca Coll-Vinent; Alfonso Martín; Juan María Sánchez; Juan Tamargo; Coral Suero; Francisco Malagón; Mercedes Varona; Manuel Cancio; Susana Campoy Sánchez; José Carbajosa; José Ríos; Georgina Casanovas; Carles Ràfols; Carmen del Arco

Background and Purpose— Long-term benefits of initiating stroke prophylaxis in the emergency department (ED) are unknown. We analyzed the long-term safety and benefits of ED prescription of anticoagulation in atrial fibrillation patients. Methods— Prospective, multicenter, observational cohort of consecutive atrial fibrillation patients was performed in 62 Spanish EDs. Clinical variables and thromboprophylaxis prescribed at discharge were collected at inclusion. Follow-up at 1 year post-discharge included data about thromboprophylaxis and its complications, major bleeding, and death; risk was assessed with univariate and bivariate logistic regression models. Results— We enrolled 1162 patients, 1024 (88.1%) at high risk according to CHA2DS2-VASc score. At ED discharge, 935 patients (80.5%) were receiving anticoagulant therapy, de novo in 237 patients (55.2% of 429 not previously treated). At 1 year, 48 (4.1%) patients presented major bleeding events, and 151 (12.9%) had died. Anticoagulation first prescribed in the ED was not related to major bleeding (hazard ratio, 0.976; 95% confidence interval, 0.294–3.236) and was associated with a decrease in mortality (hazard ratio, 0.398; 95% confidence interval, 0.231–0.686). Adjusting by the main clinical and sociodemographic characteristics, concomitant antiplatelet treatment, or destination (discharge or admission) did not affect the results. Conclusions— Prescription of anticoagulation in the ED does not increase bleeding risk in atrial fibrillation patients at high risk of stroke and contributes to decreased mortality.

Collaboration


Dive into the Juan María Sánchez's collaboration.

Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Petia Radeva

University of Barcelona

View shared research outputs
Top Co-Authors

Avatar

Alfonso Martín

Autonomous University of Barcelona

View shared research outputs
Top Co-Authors

Avatar

Blanca Coll-Vinent

Autonomous University of Barcelona

View shared research outputs
Top Co-Authors

Avatar

Carles Ràfols

Autonomous University of Barcelona

View shared research outputs
Top Co-Authors

Avatar

Carmen del Arco

Autonomous University of Barcelona

View shared research outputs
Top Co-Authors

Avatar

Coral Suero

Autonomous University of Barcelona

View shared research outputs
Top Co-Authors

Avatar

Francisco Malagón

Autonomous University of Barcelona

View shared research outputs
Researchain Logo
Decentralizing Knowledge