Latency handling for interconnected devices

Abstract

A data processing system comprises a cluster of devices ( 16 ) interconnected for the communication of data in streams, particularly digital audio and/or video data. One of the devices ( 10 ) is a source device for at feast two data streams to be sent to one or more other devices ( 12, 14 ) as destination devices of the cluster. To enable synchronisation of the stream presentations by the destination devices, some or all of the devices ( 10, 12, 14 ) carry respective tables ( 11, 13, 15 ) identifying, for that device, an identifier for each type of data stream that the device can process together with the processing delay for that stream. The or each such table is accessible via the cluster connection ( 18 ) to whichever of the devices, at source, destination or in between for the signal, is handling application of the necessary offsets.

1 . A data processing system comprising a cluster of devices interconnected for the communication of data in streams wherein, for at least two data streams to be sent to one or more devices as destination devices of said cluster, at least one device of the cluster comprises means arranged to apply a respective delay to at least one of said at least two data streams in an amount determined by differing signal path latencies for said at least two streams; wherein at least some devices of the cluster maintain a respective table, readable via said interconnection by other devices of said cluster, each such table identifying one or more latencies for the respective device, and the means arranged to apply a delay operating to apply delays on the basis of table contents.  
     
     
         2 . A system as claimed in  claim 1 , wherein each table identifies, for its respective device, signal processing capabilities for that device, together with the latency associated with each such capability.  
     
     
         3 . A system as claimed in  claim 1 , wherein one of said devices is a source device for said at least two data streams to be sent to said destination devices of said cluster, said source device including said means arranged to apply a delay together with means arranged to read data from said respective tables of the destination devices and determine the respective delay to apply to at least one of said at least two data streams.  
     
     
         4 . A system as claimed in  claim 3 , wherein said source device further comprises multiplexing means coupled with said means arranged to apply a delay and arranged to combine said at least two streams into a single data stream for transmission to said destination devices.  
     
     
         5 . A system as claimed in  claim 2 , wherein one or more table entries is in the form of an algorithm requiring data from the device reading the table to enable determination of the latency of the device holding said table.  
     
     
         6 . A system as claimed in  claim 5 , wherein the determination on the basis of the algorithm is implemented by the device reading the table, said device having downloaded the algorithm from the device holding the table.  
     
     
         7 . A system as claimed in  claim 5 , wherein the determination on the basis of the algorithm is implemented by the device holding the table, the results of the implementation being transmitted via said interconnection to the device reading the table.  
     
     
         8 . A system as claimed in  claim 1 , wherein all destination devices maintain a respective table.  
     
     
         9 . A system as claimed in  claim 1 , wherein said means arranged to apply a delay comprises buffering means.  
     
     
         10 . A system as claimed in  claim 1 , wherein said means arranged to apply a delay comprises means arranged to selectively apply a delay to reading of one or each of said data streams from a source thereof.  
     
     
         11 . (canceled)  
     
     
         12 . (canceled)