A system of distributing video and/or audio information employs digital signal processing to achieve high rates of data compression. The compressed and encoded audio and/or video information is sent over standard telephone, cable or satellite broadcast channels to a receiver specified by a subscriber of the service, preferably in less than real time, for later playback and optional recording on standard audio and/or video tape.

Audio and video transmission and receiving system

A public switched telephone network (PSTN) (10) provides digital video signals from a video information provider (140, 160) to one or more of a plurality of subscriber premises (100, 120). A subscriber uses either a standard telephone instrument (102) over the PSTN or a dedicated control device (130, 132) over an ISDN packet network (38) to order video programming. The request is transmitted to a designated video information provider (140, 160) and digital transmission connectivity is established between the video information provider (140, 160) and the central office serving the subscriber. Connectivity between the central office and subscriber is provided by asymmetrical digital subscriber line interface units over a local loop. The interface units frequency multiplex digital video information with voice information to the subscriber and support transmission of a reverse control channel from the subscriber to the central office for transmission on the ISDN packet data network (38) back to the video information provider (140, 160). The interfaces also allow base band signalling and audio between the central office and the subscriber for conventional telephone instrument connectivity.

Pstn architecture for video-on-demand services.

A public switched telephone network (PSTN) provides digital video signals from a video information provider or digital service bureau to one or more of a plurality of subscriber premises. Administration of orders from subscribers is carried out by a video gateway and file servers at the central office. Asymmetrical digital subscriber line interface (ADSL) units over a local loop carry the necessary signalling between the subscribers and information providers. The interface units frequency multiplex digital video information with voice information to the subscriber and support transmission of a reverse control channel from the subscriber to the central office for transmission back to the information provider. Several enhancements and special features are disclosed.

Video-on-demand services using public switched telephone network

A public switched telephone network for providing information from a multimedia information server to any one of a plurality of subscriber premises, comprises a central office receiving multimedia information signals from a multimedia information server and orders from a prescribed subscriber. The central office includes a gateway system for conveying routing data in response to subscriber orders and a switch for routing multimedia signals from the server to the prescribed subscriber in accordance with the routing data. An interface at the central office transmits and receives audio telephone service signals, subscriber control signals and digital multimedia information signals on first, second and third signal channels. Each subscriber premises includes an interface for transmitting and receiving audio telephone service signals, subscriber control signals and digital multimedia information signals on the three signal channels. A plurality of subscriber local loops interconnect each subscriber interface and the central office interface. Multimedia information is collected from information providers and stored at media servers that provide a library of data and control sessions. Software modules at the media servers and resident terminals enable interactive multimedia session building, sharing of databases and joint authoring of multimedia presentations.

Method and system for accessing multimedia data over public switched telephone network

Overview of the p×64 kbit/s video coding standard

The key factors deterring the use of visual telephony are identified, and an overview of a typical system architecture is given. The video signal formats and video and audio coding algorithms used are described. Video codec implementation is considered, and an implementation based on application-specific integrated circuits is presented. In particular, three key signal processing modules in the video codec are examined: a discrete cosine transform chip, a motion estimation chip, and a variable-length codec chip. Standardization activities in the video coding area are discussed. >

M.L. Liou

Papers

Visual telephony as an ISDN application