Methods of transmitting and receiving compressed television signals

Abstract

The invention relates to the transmission of MPEG encoded television signals from a Video-On-Demand server ( 1 ) to a receiver ( 2 ) via a network ( 3 ). Non-linear playback functions such as ‘pause’ and ‘resume’ require a very accurate control of the bit stream, taking account of typical network aspects such as network latency and remultiplexing. In order to allow the receiver to flawlessly resume signal reproduction after a pause, position labels (p; 5, 6; 7 a , 7 b , 8 a , 8 b ) are inserted into the bit stream at positions where the server can resume transmission of the signal after an interruption. Upon a pause request, the decoder initially continues the reproduction until such a position label is detected. The subsequent bits delivered by the network are ignored, i.e. they are thrown away. Upon a request to resume reproduction, the receiver requests the server to retransmit the signal starting at the detected position.

1 . A method of transmitting a compressed television signal, comprising the steps of: 
 generating a stream of transport packets from the compressed television signal;    inserting position labels into the stream of transport packets at positions within said signal where the transmission of said signal can be resumed after an interruption; and    transmitting said stream of transport packets.    
     
     
         2 . The method as claimed in  claim 1 , wherein the position labels are accommodated in intermediate control packets.  
     
     
         3 . The method as claimed in  claim 2 , wherein the position labels are transmitted as MPEG stream descriptors in said control transport packets.  
     
     
         4 . The method as claimed in  claim 1 , wherein the position labels are accommodated in said packets.  
     
     
         5 . The method as claimed in  claim 4 , in which the position labels are transmitted as private data bytes in the adaptation field of MPEG transport packets.  
     
     
         6 . A method of receiving a compressed television signal from a transmitter, characterized by the steps of: 
 sending a request to the transmitter to interrupt transmission of the signal;    interrupting the reproduction of the signal upon detection of a position label inserted into said signal by the transmitter, and throwing away the received signal following said position label;    sending a request to the transmitter to resume transmission of the signal from the position defined by said position label; and    resuming the reproduction of the signal upon receipt thereof.    
     
     
         7 . A transmitter for transmitting a compressed television signal, comprising: 
 means for generating a stream of transport packets from the compressed television signal;    by means for inserting position labels into the stream of transport packets at positions within said television signal where the transmission of said television signal can be interrupted and resumed; and    means for transmitting said stream of transport packets.    
     
     
         8 . The transmitter as claimed in  claim 7 , wherein the transmitter is adapted to accommodate said position labels in intermediate control packets.  
     
     
         9 . The transmitter as claimed in  claim 8 , wherein the position labels are transmitted as descriptors in MPEG transport packets.  
     
     
         10 . The transmitter as claimed in  claim 7 , wherein the transmitter is adapted to accommodate said position labels in selected ones of said transport packets.  
     
     
         11 . The transmitter as claimed in  claim 10 , in which the position labels are transmitted as private data bytes in the adaptation field of MPEG transport packets.  
     
     
         12 . A receiver for receiving a compressed television signal, wherein the receiver comprises control means adapted to: 
 send a request to a transmitter to interrupt transmission of the signal;    interrupt the reproduction of the signal upon detection of a position label inserted into the signal by the transmitter, and throw away the received signal following said position label;    send a request to the transmitter to resume transmission of the signal from the position defined by said position label; and    resume the reproduction of the signal upon receipt thereof.    
     
     
         13 . A compressed television signal, including a stream of transport packets having position labels inserted into the stream of transport packets at positions within said signal where the transmission of said signal can be resumed after an interruption.