Abstract: Unauthorized entry into controlled access areas using tailgating or reverse entry methods is detected using machine vision methods. Camera images of the controlled area are processed to identify and track objects in the controlled area. In a preferred embodiment, this processing includes 3D surface analysis to distinguish and classify objects in the field of view. Feature extraction, color analysis, and pattern recognition may also be used for identification and tracking of objects. Integration with security monitoring and control systems provides notification when a tailgating or reverse entry event has occurred. More reliable operation in practical circumstances is thus obtained, such as when multiple people are using an entrance or exit under variable light and shadow conditions. Electronic access control systems may further be combined with the machine vision methods of the invention to more effectively prevent tailgating or reverse entry.

Abstract: Unauthorized entry into controlled access areas using tailgating or reverse entry methods is detected using machine vision methods. Camera images of the controlled area are processed to identify and track objects in the controlled area. In a preferred embodiment, this processing includes 3D surface analysis to distinguish and classify objects in the field of view. Feature extraction, color analysis, and pattern recognition may also be used for identification and tracking of objects. Integration with security monitoring and control systems provides notification when a tailgating or reverse entry event has occurred. More reliable operation in practical circumstances is thus obtained, such as when multiple people are using an entrance or exit under variable light and shadow conditions. Electronic access control systems may further be combined with the machine vision methods of the invention to more effectively prevent tailgating or reverse entry.

Abstract: In a broadcast system in which computer data and other content are delivered from multiple content servers to multiple clients at least partly over a broadcast network, a transmission announcement system announces upcoming broadcast transmissions and instructs the clients on how to receive the broadcast transmissions. Announcement servers (which may or may not be the same as the content servers which serve the data for the broadcast transmissions) generate announcements containing information specifying how associated upcoming transmissions are to be delivered over the broadcast network. The announcement server makes the announcements available to the clients over the broadcast network or over a secondary link other than the broadcast network.

Abstract: In a broadcast system in which computer data and other content are delivered from multiple content servers to multiple clients at least partly over a broadcast network, a transmission announcement system announces upcoming broadcast transmissions and instructs the clients on how to receive the broadcast transmissions. Announcement servers (which may or may not be the same as the content servers which serve the data for the broadcast transmissions) generate announcements containing information specifying how associated upcoming transmissions are to be delivered over the broadcast network. The announcement server makes the announcements available to the clients over the broadcast network or over a secondary link other than the broadcast network.

Abstract: Unauthorized entry into controlled access areas using tailgating or reverse entry methods is detected using machine vision methods. Camera images of the controlled area are processed to identify and track objects in the controlled area. In a preferred embodiment, this processing includes 3D surface analysis to distinguish and classify objects in the field of view. Feature extraction, color analysis, and pattern recognition may also be used for identification and tracking of objects. Integration with security monitoring and control systems provides notification when a tailgating or reverse entry event has occurred. More reliable operation in practical circumstances is thus obtained, such as when multiple people are using an entrance or exit under variable light and shadow conditions. Electronic access control systems may further be combined with the machine vision methods of the invention to more effectively prevent tailgating or reverse entry.

Abstract: In a broadcast system in which computer data and other content are delivered from multiple content servers to multiple clients at least partly over a broadcast network, a transmission announcement system announces upcoming broadcast transmissions and instructs the clients on how to receive the broadcast transmissions. Announcement servers (which may or may not be the same as the content servers which serve the data for the broadcast transmissions) generate announcements containing information specifying how associated upcoming transmissions are to be delivered over the broadcast network. The announcement server makes the announcements available to the clients over the broadcast network or over a secondary link other than the broadcast network.

Abstract: A webcast system delivers Web content from a webcast center over a broadcast medium to many clients. The webcast center has a server unit that gathers Web pages from sites on the Internet and stores the pages in a cache. The server unit bundles the pages from the cache into package files and stores the package files in a package store. The webcast center also has a broadcast unit that retrieves the package files from the package store and delivers the package files to the clients over the broadcast medium. Each client is equipped with a receiver to receive the broadcast package files. The client maintains a subscription database to store a directory of the Web content gathered by the webcast center. A subscriber user interface enables a user to select preferred Web content from the directory of the subscription database.

Abstract: In a broadcast system in which computer data and other content are delivered from multiple content servers to multiple clients at least partly over a broadcast network, a transmission announcement system announces upcoming broadcast transmissions and instructs the clients on how to receive the broadcast transmissions. Announcement servers (which may or may not be the same as the content servers which serve the data for the broadcast transmissions) generate announcements containing information specifying how associated upcoming transmissions are to be delivered over the broadcast network. The announcement server makes the announcements available to the clients over the broadcast network or over a secondary link other than the broadcast network.

Abstract: A data delivery system facilitates transmission of data packets from a content server to multiple clients over a unidirectional network. A redundancy formatter resident at the server groups multiple data packets into a redundancy group and generates at least one redundancy packet containing redundancy information derived from the data packets in the redundancy group. The data packets and redundancy packet are sent over the unidirectional network to the client. In the event that a packet is lost, a packet rebuilder resident at each client reconstructs the missing data packet from the successfully transmitted data packets in the redundancy group and the redundancy packet for the redundancy group.