SIGNAL CODING FOR SECURE TRANSMISSION

摘要

A multiplexed analogue component (MAC) television signal is encrypted for transmission and reception by authorised recipients only by dividing the signal into blocks and reordering the blocks prior to transmission. The signal within each block remains in its original order. Preferably, the signal representing one line of video is split into blocks which are reordered within the line time to cause translation or rotation of analogue components. Alternatively group of lines may be processed as a group to cause reordering of the analogue components between lines. The preferred arrangement does not split the blocks of analogue signals already present in the MAC signal. The receiver is arranged to receive information regarding the encryption technique with the television signal and to reorder the blocks constituting the received signal whereby to reconstruct the original signal.