Archive for the ‘science’ Category
Posted by eduardovalle on Monday, June 21, 2010
Ana Lopes, a student of Prof. Arnaldo Araújo and Prof. Jussara de Almeida, has compiled an impressive survey on human action recognition for her Ph.D. thesis. The analysis of that corpus, especially the recent literature, has prompted us to propose a new way to categorize the existing methods, using the underlying data representation as the main criterium of organization. The abstract explains the rationale behind that choice:
This paper presents a survey of human action recognition approaches based on visual data recorded from a single video camera. We propose an organizing framework which puts in evidence the evolution of the area, with techniques moving from heavily constrained motion capture scenarios towards more challenging, realistic, “in the wild” videos. The proposed organization is based on the representation used as input for the recognition task, emphasizing the hypothesis assumed and thus, the constraints imposed on the type of video that each technique is able to address. Expliciting the hypothesis and constraints makes the framework particularly useful to select a method, given an application. Another advantage of the proposed organization is that it allows categorizing newest approaches seamlessly with traditional ones, while providing an insightful perspective of the evolution of the action recognition task up to now. That perspective is the basis for the discussion in the end of the paper, where we also present the main open issues in the area.
The survey was submitted for peer review at the CVIU, and is available as a preprint at arxiv.org.
Posted in science | Tagged: action recognition, Ana Lopes, Arnaldo Araújo, CVIU, DCC / UFMG, human actions, Jussara de Almeida, paper, publication, survey | Leave a Comment »
Posted by eduardovalle on Wednesday, April 21, 2010
Our paper, “MONORAIL: A Disk-Friendly Index for Huge Descriptor Databases” was accepted at the upcoming IAPR Internation Conference on Pattern Recognition — ICPR 2010. Here is the abstract:
We propose MONORAIL, an indexing scheme for very large multimedia descriptor databases. Our index is based on the Hilbert curve, which is able to map the high-dimensional space of those descriptors to a single dimension. Instead of using several curves to mitigate boundary effects, we use a single curve with several surrogate points for each descriptor. Thus, we are able to reduce the random accesses to the bare minimum. In a rigorous empirical comparison with another method based on multiple surrogates, ours shows a significant improvement, due to our careful choice of the surrogate points.
I am particularly proud of this paper, not only because of the method itself, but also because of the experimental design we propose for the validation. I have been studying for more than a year the topics of Design of Experiments, statistical tests and validation. This is the first of a crop of publications that are employing those rigorous evaluation tools, which, though commonplace in other fields, are still seldom used in Computer Sciences.
Posted in publications, science | Tagged: conference, design of experiments, Fernando Akune, kNN search, monorail, paper, publication, Ricardo Torres | Leave a Comment »
Posted by eduardovalle on Wednesday, April 14, 2010
I have just arrived (suitcases still to be undone) from my trip to the USA. This time, I went to Philadelphia for the MIR Conference, where I have presented a poster on the work of my student Fábio Faria. I have met many interesting people at MIR and heard exciting, new ideas from them, but (without any intention to dismiss the hard work of the organizers) I must confess I was expecting a more diverse array of works (especially considering how broad the “Multimedia” community is).
Instead, I was astonished by how much the presented selection was similar in terms of technical foundation: classification based on discriminant approach (almost always using SVM) and representation based on “bags of visual features”. It is not that those do not interest me — after all, our own work is sits squarely on those pillars — but I was very interested in hearing about, seeing other approaches: generative models based on latent or explicit semantics, representations based on constellation models — what do I know ? — perhaps something completely new, which I haven’t even heard about.
I was left wondering why those “competing theories” were so notably absent. Has the community decided that SVM + Bags of Features is so conspicuously better than everything else ? (If that is the case, I would like to know how they reached this conclusion — though I like the results given by the pair “bags + SVM”, I am far from considering the “case closed”).
Was it self-selection by the autors, who didn’t submit their works to this particularly community ?
Or — and this is obviously the worst scenario— have all the alternative works been retained at the peer review barrier, because ideological considerations have (maybe unconsciously?) tainted the assessment of quality. I would like to quick dismiss this latter possibility, but the similarity between the works was really astounding. My student Otávio Penatti, who is on his first months of Ph.D. (he was there presenting a demo of his M.Sc. work) remarked it immediately.
I was very glad, nevertheless, to have this opportunity to visit Philadelphia. It was a very moving experience for me, because it gave me a very concrete, very immediate realization of how strongly The Enlightenment was shining in America at that time.
* * *
Otávio and I have profited from our travel to the USA to visit Prof. Edward Fox in Virginia Tech, who was the former Ph.D. advisor of Otávio’s current Ph.D. avidsor and my Post-Doc advisor Prof. Ricardo Torres. We have an ongoing cooperation with Prof. Fox. In fact, while we were there, we have met a Brazilian colleague of ours, Nadia Kozievitch, who is spending an year of her Ph.D. with Prof. Fox.
While we were there, we gave a talk on our current work and got acquainted with several exciting projects Prof. Fox is conducting, on a broad array of applications of digital libraries, including identification of fingerprints, biodiversity databases, e-Science, cooperation for crisis situations, and education.
We have also met Brazilian Prof. João Setúbal, who showed us the Virginia Bioinformatics Institute, and talked about his work in genomics, and the new field of transcriptonics.
We were very impressed not only with the infra-structure of Virginia Tech, but also with the kindness and attentiveness of everyone who received us.
Posted in career, science | Tagged: paper, publication, cooperation, UNICAMP, Ricardo Torres, Fábio Faria, USA, Edward Fox, João Setúbal, Otávio Penatti, Nadia Kozievitch, Virginia Tech, bioinformatics, MIR 2010 | 2 Comments »
Posted by eduardovalle on Friday, March 5, 2010
Our new lab RECOD now has not only a cool name and logo but also money to finance its first two years of operation. We have just been informed that the Brazilian sponsoring agency FAPESP has approved our project. The project is coordinated by my post-doc supervisor Prof. Ricardo Torres and was co-authored by Prof. Anderson Rocha, Prof. Helio Pedrini, Prof. Jacques Wainer, Prof. João Cavalcanti, Prof. Siome Goldenstein and me. Prof. Pedrini (our colleague from UNICAMP) and Prof. Cavalcanti (from UFAM) entered not as members of the lab, but as cooperating partners in the project.
Posted in science | Leave a Comment »
Posted by eduardovalle on Tuesday, February 16, 2010
Together with Prof. Anderson Rocha, Prof. Jacques Wainer, Prof. Ricardo Torres (my Post Doc advisor, by the way) and Prof. Siome Goldenstein, we have recently founded a new laboratory at the Computing Institute of the State University of Campinas (UNICAMP).
The new lab — which we named RECOD — aims to embrace the research subjects of machine learning, multimedia retrieval and classification, multimodality and digital forensics.
The foundation of this new lab both celebrates a history of fruitful colaboration between its participating members and inaugurates a new phase of tighter cooperation, in which the synergy of our complementary competencies will be fostered in an optimized environment.
I cannot avoid to be proud that my colleagues have accepted both my name and logo suggestions for the new lab.
Long live RECOD !
Posted in science | Tagged: Anderson Rocha, digital forensics, Jacques Wainer, machine learning, multimedia, RECOD, Ricardo Torres, Siome Goldenstein, UNICAMP | Leave a Comment »
Posted by eduardovalle on Friday, January 22, 2010
Our paper, “Learning to Rank for Content-Based Image Retrieval” , was accepted at the upcoming ACM Multimedia Information Retrieval Conference (MIR 2010). The first author is the M.Sc. student Fábio Faria, and the paper was co-authored with my Post Doc supervisor Ricardo Torres and several of our partners from UFMG, including Marcos Gonçalves, with whom we have an ongoing cooperation.
Here is the abstract:
“In Content-based Image Retrieval (CBIR), accurately ranking the returned images is of paramount importance, since users consider mostly the topmost results. The typical ranking strategy used by many CBIR systems is to employ image content descriptors, so that returned images that are most similar to the query image are placed higher in the rank. While this strategy is well accepted and widely used, improved results may be obtained by combining multiple image descriptors. In this paper we explore this idea, and introduce algorithms that learn to combine information coming from different descriptors. The proposed learning to rank algorithms are based on three diverse learning techniques: Support Vector Machines (CBIR-SVM), Genetic Programming (CBIR-GP), and Association Rules (CBIR-AR). Eighteen image content descriptors (color, texture, and shape information) are used as input and provided as training to the learning algorithms. We performed a systematic evaluation involving two complex and heterogeneous image databases (Corel e Caltech) and two evaluation measures (Precision and MAP). The empirical results show that all learning algorithms provide significant gains when compared to the typical ranking strategy in which descriptors are used in isolation. We concluded that, in general, CBIR-AR and CBIR-GP outperforms CBIR-SVM. A fine-grained analysis revealed the lack of correlation between the results provided by CBIR-AR and the results provided by the other two algorithms, which indicates the opportunity of an advantageous hybrid approach.”
I will be travelling to Philadelphia on late March to present the poster. I am very excited about this upcoming trip to the United States, where I am to meet several friends and colleagues, but at the same time, worried about the radicalization of air security rules and the exaggeration of perception of threats. Have we got so scared to die that we decided instead not to live ?
Posted in publications, science | Tagged: paper, conference, publication, cbir, DCC / UFMG, Ricardo Torres, poster, MIR, learn to rank, machine learning, Fábio Faria, Marcos Gonçalves | Leave a Comment »
Posted by eduardovalle on Sunday, September 20, 2009
I guess that for all people involved, DocEng’09 was a success. Like last year, the conference was small — I think that we were 60 or 70 participants — but the quality of the works presented was high, and the scientific exchange was extremely interesting. In DocEng, you get to meet everyone individually, something which is unfeasible at large-scale conferences.
Thematically, the conference has a broad scope, centered around the representation, processing, analysis, storage and retrieval of documents. My main research topic concerns the retrieval of multimedia documents, and is somewhat at the fringe of the conference theme. Nevertheless, people seemed genuinely interested and I’ve got many useful insights and suggestions.
* * *
I have just arrived at Paris, where I will meet my former Ph.D. supervisor Prof. Matthieu Cord, among other colleagues. I intend to advance our research on high-dimensional multimedia indexing and large scale multimedia retrieval. I am also giving a talk about my current research pursuits at the ETIS labs, on Cergy-Pontoise, next Tuesday, September 22nd.
If you use Google Calendar you can save the date by clicking below:
Posted in publications, science | Tagged: cooperation, doceng, etis, France, Germany, lip6, publication, seminar | Leave a Comment »
Posted by eduardovalle on Sunday, July 5, 2009
I had two short papers accepted on DocEng 2009.
One, co-authored with my French partners Dr. David Picard and Prof. Matthieu Cord, is about the difficult problem of enforcing geometric consistency in vote-counting based CBIR when there are too many outliers — a situation we encounter routinely in our iTowns project. Here’s the title and abstract:
Geometric Consistency Checking for Local-Descriptor Based Document Retrieval — In this paper, we evaluate different geometric consistency schemes, which can be used in tandem with an efficient architecture, based on voting and local descriptors, to retrieve multimedia documents. In many contexts the geometric consistency enforcement is essential to boost the retrieval performance. Our empirical results show however, that geometric consistency alone is unable to guarantee high-quality results in databases that contain too many non-discriminating descriptors.
The other, co-authored with my Brazilian colleagues Flávio Bertholdo and Prof. Arnaldo Araújo, proposes a new method for contrast enhancement in degraded historical documents, which takes into account the structure of the the document:
Layout-Aware Limiarization for Readability Enhancement of Degraded Historical Documents — In this paper we propose a technique of limiarization (also known as thresholding or binarization) tailored to improve the readability of degraded historical documents. Limiarization is a simple image processing technique, which is employed in many complex tasks like image compression, object segmentation and character recognition. The technique also finds applications on itself: since it results in a high-contrast image, in which the foreground is clearly separated from the background, it can greatly improve the readability of a document, provided that other attributes (like character shape) do not suffer. Our technique exploits statistical characteristics of textual documents and applies both global and local thresholding. Under visual inspection on experiments made in a collection of severely degraded historical documents, it compares favorably with the state of the art.
DocEng 2009 will be held in Munich, Germany on September 15–18.
EDIT 23/07: The preprints are now available in my publications page.
Posted in publications, science | Tagged: paper, doceng, publication, cultural heritage, cbir, limiarization, iTowns, geometric consistency | Leave a Comment »
Posted by eduardovalle on Friday, May 8, 2009
I’ve been invited by Prof. Francisco Pelaez and Prof. Camila Barione of the Centre of Mathematics Computing and Cognition of the Federal University of ABC to give my talk on kNN Search and CBIR (Content Based Image Retrieval).
I will discuss my past work, showing the three methods I’ve proposed during my thesis on high-dimensional multimedia indexing on large databases. But I also discuss some of my new research pursuits, related to the use of very discriminant local descriptors, like SIFT, on complex semantic queries, which require generalisation.
The talk, in Portuguese, will be on Tuesday May 26, at the Block B, room A801 of the Federal University of the ABC, which is located at the Rua Santa Adélia, 166, Santo André — SP, Brazil, CEP 09210-170. Their phone number is +55 11 4996-3166.
If you have a Google Calendar, you can save the date by clicking below:
Posted in science | Tagged: multicurves, kNN search, thesis, Brazil, cbir, indexing, projection kd-forests, 3-way trees, seminar, UFABC | 2 Comments »
Posted by eduardovalle on Tuesday, April 21, 2009
Prof. Ricardo Torres has invited me to the Institute of Computing of the State University of Campinas, where I am giving a talk on the work I’ve done on my thesis. I will explore the challenges of kNN search (also known as k nearest neighbours search, or simply similarity search) and discuss the three original methods I’ve proposed: the 3-way trees, which are based on the traditional KD-Tree with the addition of redundant overlapping nodes; the projection KD-Forests, my first attempt of using an index composed of multiple moderate-dimensional sub-indexes; and finally the Multicurves, an index based on the use of multiple moderate-dimensional space-filling curves, which has several nice properties like ease of implementation, dynamicity (tolerance to insertions and deletions without performance degradation) and avoidance of random accesses (thus making secondary-memory implementation easier).
The talk will be in Portuguese.
Posted in science | Tagged: 3-way trees, Brazil, indexing, kNN search, multicurves, projection kd-forests, seminar, thesis, UNICAMP | Leave a Comment »
