Scientific-atlanta, Inc.

Douglas F Woodhead

Anthony John Wasilewski

Gary L Logston

Arturo A Rodriguez

Howard G Pinder

Ajith N Nair

Luis A Rovira

Maynard Darvel Hammond

William D Woodward

David B Burleson

Paul Rimas Zalkauskas

Richard A Powers

A device in a subscriber television system receives a stream of frames of information, and each frame of information is carried in at least one network packet that is formatted according to a first protocol. Each network packet carries an application packet that is formatted according to a second protocol, which is a protocol for an application. The device includes application awareness that enables the device to selectively modify the application packets.

Information frame modifier

A control system provides secure transmission of programs, including at least one of video, audio, and data, between a service provider and a customer's set top unit over a digital network. Program bearing data packets are received in a first network protocol over a first data link and removed from the first network protocol. Packets representing a particular program requested by a customer having a set top unit are selected. Conditional access is provided to the selected program. In particular, program bearing packets are encrypted according to a first encryption algorithm using a first key, which is then encrypted according to a second encryption algorithm using a second key. The first keys are transported in packets to the customer's set top units along with the program packets. A public key cryptographic technique encrypts the second key such that the public key used in the encryption corresponds to the private key of the customer's set top unit. After the conditional access layers have been added, the packets are encapsulated and output in a second network protocol destined for the set top unit.

Method and apparatus for providing conditional access in connection-oriented interactive networks with a multiplicity of service providers

A control system provides secure transmission of programs, including at least one of video, audio, and data, between a service provider and a customer's set top unit over a digital network. Program bearing data packets are recieved in a first network protocol over a first data link and removed from the first network protocol. Packets representing a particular program requested by a customer having a set top unit are selected. Conditional access is provided to the selected program. In particular, program bearing packets are encrypted according to a first encryption algorithm using a first key, which is then encrypted according to a second encryption algorithm using a second key. The first keys are transported in packets to the customer's set top units along with the program packets. A public key cryptographic technique encrypts the second key such that the public key used in the encryption corresponds to the private key of the customer's set top unit. After the conditional access layers have been added, the packets are encapsulated and output in a second network protocol destined for the set top unit.

Method and apparatus for providing conditional access in

In a system that transmits packets containing timestamps and information from a transmission site to a reception site at a transmission bit rate the packets may experience jitter, i.e. variable delay, during transmission. In such a case, the packets are temporally shifted relative to the timestamps and to other packets. Where the timestamp values are inserted into selected packets prior to transmission and that timestamp represent the value of the transmission site clock, the method and apparatus of the present invention substantially removes the jitter and adjusts the timestamp values prior to reception of the packets at the reception site. The present invention achieves this goal by receiving the packets at an intermediate site that has a local clock operates at a nominal frequency substantially equal to the nominal frequency of the transmission site clock and uses that clock as a jitter-free clock to correct the packets. The packets are stored in a buffer at the intermediate site and output from the buffer at a controlled rate to maintain a substantially constant average transit time of packets through the buffer. Before the packets are output for reception at the reception site the timestamps of selected packets are modified to reflect the new temporal relationship between packets due to the controlled rate of output from the intermediate site.

Method and apparatus for removing jitter and correcting timestamps in a

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Lawrenceville, GA, United States of America

Douglas F Woodhead