Interactive distribution system for digital audio-video signals

• US 6,032,181 A
• Filed: 02/11/1999
• Issued: 02/29/2000
• Est. Priority Date: 02/25/1998
• Status: Expired due to Fees

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Teboul, Guillene, Bedgedjian, Jean C.
• Primary Examiner(s): Faile, Andrew I.
• Assistant Examiner(s): TRAN, HAI V
• Application Number:
  US09/248,534
• Time in Patent Office: 383 Days
• Field of Search: 348/12, 348/13, 709/217, 370/394, 370/503, 370/509, 370/511, 370/512, 370/513
• US Class Current: 725/121
• CPC Class Codes: H04J 3/0632 Synchronisation of packets and cells, e.g. transmission of voice via a packet network, circuit emulation service [CES] queuing arrangements in packet switching elements H04L49/90; synchronising systems for the synchronous transmission of a pulse code modulated video signal with one or more other pulse code modulated signals H04N7/56
• CPC Class Codes: H04J 3/0682 by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging
• CPC Class Codes: H04L 7/04 Speed or phase control by synchronisation signals H04L7/0075 takes precedence
• CPC Class Codes: H04N 21/242 Synchronization processes, e.g. processing of PCR [Program Clock References] arrangements for synchronising broadcast or distribution via plural systems in broadcast distribution systems H04H20/18
• CPC Class Codes: H04N 21/4302 Content synchronisation processes, e.g. decoder synchronisation

Abstract

In an interactive audio-video digital distribution system a pointer is transmitted at least once every T milliseconds to indicate the position of a time marker. An interruption (V) occurs every T milliseconds. A given number N of integer frames being transmitted in T milliseconds, there remains only space for transmitting a portion containing R symbols of the N+^th frame before the next interruption. Following transmission of a signaling packet (x) with a pointer indicating a number (x) of symbol periods, during the next interruption N packets will have been completely transmitted since the last pointer, plus R symbols. The end of the transmission of this packet is waited for, that is, U═C-R symbol periods before a new signaling packet (x-U) is transmitted. The value of the pointer contained in this packet will thus have to take this offset into account as it is decremented by U symbols, that is, x-U, and so on.

Claims

1. An interactive distribution system for audio-video signals, having a channel called downstream channel and a channel called upstream channel, the downstream channel transmitting signals in the form of digital packets from a server to users, a clock intended for multiplexing upstream messages from the users to the server being defined by markers whose position is periodically indicated by a number, called pointer, incorporated in one of the packets of the downstream channel, this pointer indicating the time that is left between the moment where the pointer appears and the moment where the marker is placed, characterized in that the system comprises means for generating a packet containing a pointer at an instant offset relative to that at which it should have been generated, and for diminishing the value of this pointer by a quantity equal to the time that has elapsed since the instant at which the packet containing the pointer would have had to be generated and the instant at which it is generated.

2. An audio-video signal for a system having a channel called downstream channel and a channel called upstream channel, which signal is transmitted in the downstream channel in the form of packets and comprises, inter alia, a clock, used for the multiplexing of messages in the upstream channel, defined by markers whose position is periodically indicated by a pointer incorporated in one of the packets, the value of this pointer indicating the time that is left between the moment where the pointer appears and the moment where the marker is placed, characterized in that a packet containing a pointer is generated at an instant offset relative to that at which it would have had to be generated, and the value of this pointer is dimished by a quantity equal to the time that has elapsed between the instant at which the packet containing the pointer would have had to be generated and the instant at which it is generated.

3. Method of calculating in an interactive digital audio-video signal distribution system that transmits signals from a server to users in the form of packets, the value of a pointer indicating the position of a time marker incorporated in one of the packets, the value of this pointer indicating the time that is left between the moment where the packet containing the pointer appears and the moment where the marker is placed, characterized in that the method comprises that a packet containing a pointer is generated at an instant offset relative to that at which it would have had to be generated, and that the value of this pointer is diminished by a quantity equal to the time that has elapsed between the instant at which the packet containing the pointer would have had to be generated and the instant at which it is generated.