Video signal timing in a multi-format environment

Abstract

In a video broadcast or production plant including first and second video sources which provide first and second digital video signals respectively at integer related frame rates, the video sources are operated so that the first and second video signals are aligned at a reference time. Switch points for updating a router in the plant are defined by measuring lapse of time from the reference time.

1 . A method of operating a video router in a plant including at least first and second video sources which provide first and second digital video signals respectively at integer related frame rates, said method including: 
 operating the first and second video sources so that the first and second video signals are aligned at a reference time, and    defining switch points for updating the router by measuring lapse of time from said reference time.    
     
     
         2 . A method according to  claim 1 , further comprising converting the first and second digital video signals to a common digital interface format.  
     
     
         3 . A method according to  claim 1 , wherein the first and second digital video signals are high definition video signals and the plant also includes a third video source which provides a standard definition video signal under control of a master clock signal, and wherein the master clock signal is used to control the first and second video sources and to measure lapse of time.  
     
     
         4 . A method according to  claim 1 , comprising generating a master clock signal at a frequency that is equal to, or an integer multiple of, the frame rate of the first digital video signal, and measuring lapse of time by reference to the master clock signal and periodically applied time offsets.