W-4: Real-time surveillance of people and their activities

W-4 is a real time visual surveillance system for detecting and tracking mu ltiple people and monitoring their activities in an outdoor environment. It operates on monocular gray-scale video imagery, or on video imagery from a n infrared camera. W-4 employs a combination of shape analysis and tracking to locate people and their parts (head, hands, feet, torso) and to create models of people's appearance so that they can be tracked through interacti ons such as occlusions. It can determine whether a foreground region contai ns multiple people and can segment the region into its constituent people a nd track them. W-4 can also determine whether people are carrying objects, and can segment objects from their silhouettes, and construct appearance mo dels for them so they can be identified in subsequent frames. W-4 can recog nize events between people and objects, such as depositing an object, excha nging bags, or removing an object. It runs at 25 Hz for 320x240 resolution images on a 400 Mhz dual-Pentium II PC.