Nixon & Vanderhye
Television signal standards conversion
 A television picture transmission system using conditional replenishment employs a scanning rate at the transmitter which differs (for asynchronous operation, slightly; or for operation between systems using different standards, considerably) from the scanning standard at the the receiver. The frame rate conversion is effected by the updating loops at the transmitter or receiver by, respectively, periodically stopping the coding loop for a field or frame so that no data is produced to produce a lower frame rate or periodically repeating a field or frame in the loop without adding any updating data so as to produce a higher frame rate. Resulting variations in data rate are accommodated by utilizing the buffering inherent in conditional replenishment systems. The jerkiness of motion in the received picture resulting from stopping the loop or repeating a field or frame can be reduced by the use of temporal interpolation in the generation of the updating data to anticipate the stopping or repeating of a field or frame, while conversion of the number of lines per frame can be effected by spatial interpolating using a transversal filter. 
British Telecommunications
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Michael D. Richard C. David G.
Carr Nicol Morrison