peeking_Pritch_ICCV_07 - Webcam Synopsis Peeking Around the...

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Webcam Synopsis: Peeking Around the World Yael Pritch Alex Rav-Acha Avital Gutman Shmuel Peleg School of Computer Science and Engineering The Hebrew University of Jerusalem 91904 Jerusalem, Israel Abstract The world is covered with millions of webcams, many transmit everything in their eld of view over the Internet 24 hours a day. A web search nds public webcams in air- ports, intersections, classrooms, parks, shops, ski resorts, and more. Even more private surveillance cameras cover many private and public facilities. Webcams are an endless resource, but most of the video broadcast will be of little interest due to lack of activity. We propose to generate a short video that will be a syn- opsis of an endless video streams, generated by webcams or surveillance cameras. We would like to address queries like “I would like to watch in one minute the highlights of this camera broadcast during the past day”. The pro- cess includes two major phases: (i) An online conversion of the video stream into a database of objects and activities (rather than frames). (ii) A response phase, generating the video synopsis as a response to the user’s query. To include maximum information in a short synopsis we simultaneously show activities that may have happened at different times. The synopsis video can also be used as an index into the original video stream. 1. Introduction Millions of webcams and surveillance cameras are cov- ering the world, capturing their eld of view 24 hours a day. It is reported that in the UK alone there are 4.2 million se- curity cameras covering city streets. Many webcams even transmit their video publicly over the Internet for everyone to watch. Several web sites try to index webcams by loca- tion or by functionality, and there is still much to be done in order to better organize this endless resource. One of the problems in utilizing webcams is that they provide unedited raw data. A two hours feature lm, for ex- ample, is usually created from hundreds or even thousands This research was supported (in part) by grants from the Israeli Min- istry of Science and from Google. of hours of raw video footage. Without editing, most of the webcam data is irrelevant. Also, a viewer in one continent is likely to reach a webcam in another continent during hours of non-activity because of time-zone differences. Our work tries to make the webcam resource more use- ful by giving the viewer the ability to view summaries of the endless video, in addition to the live video stream pro- vided by the camera. To enable this, a server can view the live video feed, analyze the video for interesting events, and record an object-based description of the video. This de- scription lists for each webcam the interesting objects, their duration, location, and their appearance. In a 3D space- time description of the video, each object is a “tube”. In this paper we assume that moving objects are interesting, as well as phase transitions when a moving object turns into background and vice versa. Other criteria, e.g. using object
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This note was uploaded on 06/13/2011 for the course CAP 6412 taught by Professor Staff during the Spring '08 term at University of Central Florida.

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peeking_Pritch_ICCV_07 - Webcam Synopsis Peeking Around the...

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