A Graph Based Approach for Finding People in News


Derya Ozkan
Computer Engineering Department
Bilkent University

Along with the recent advances in technology, large quantities of multi-modal data has arisen and became prevalent. Hence, effective and efficient retrieval, organization and analysis of such data constitutes a big challenge. Both news photographs on the web and news videos on television forms this kind of data by covering rich sources of information. People are mostly the main subject of the news; therefore, queries related to a specific person are often desired.In this study, we propose a graph based method to improve the performance of person queries in large news video and photograph collections. The method is composed of four steps: integration of names and faces, construction of a similarity graph, finding the densest component of the graph, and recognition based on the constructed graph. In the first step, we exploit the multi-modal structure of the data by associating text and face information. On the assumption that a person's face is likely to appear when his/her name is mentioned in the news, only the faces associated with the query name are selected first to limit the search space for a query name. In the second step, we construct a similarity graph of the faces in this limited search space, where nodes correspond to the faces and edges correspond to the similarity between the faces.Among these faces, there could be many faces corresponding to the queried person in different conditions, poses and times. There could also be other faces corresponding to other people in the news or some non-face images due to the errors in the face detection method used. However, in most cases, the number of corresponding faces of the queried person will be large, and these faces will be more similar to each other than to others. Hence, in the third step, the problem is transformed into a graph problem, in which we seek to find the densest component of the graph. This most similar subset (densest component) is likely to correspond to the faces of the query name. In the final step, the result of the graph algorithm is used as a model for further recognition when new faces are encountered. In the paper, it has been shown that the graph approach can also be used for detecting anchorpeople without any supervision.The experiments are performed on two different data sets: news photographs and news videos. The first set consists of thousands of news photographs from Yahoo! news web site. The second set is 229 broadcast news videos provided by NIST for TRECVID 2004. Images from the both sets are taken in real life conditions and, therefore, have a large variety of poses, illuminations and expressions. The results show that proposed method outperforms the text only based methods and provides cues for recognition of faces on the large scale.


DATE: 19 July, 2007, Thursday@ 10:00