Abstract: The invention provides a system of encoding broadcast-quality television signals to enable their transmission as a embedded code.A preferred embodiment provides a hybrid interpolative/predictive coding algorithm acting on all sampled sites of a television signal. One sub-set of samples are adaptively interpolatively coded; a 3-state interpolator switching signal is produced at each site, redundancy is removed and the signal transmitted. The interpolator switching signal also acts as a descriptor at sites surrounded each sample to be predicted. Adaptive prediction is used for the other sub-set of samples the particular predictor used at a sample site being determined by the surrounding descriptors.

Abstract: A method of encrypting a television signal having in each ruster scan line a digital section of information and chrominance and luminance sections of information comprising cutting either or both of the chrominance and luminance sections and rotating the cut sections within a normal line period. If one of the sections is uncut, it may be translated in time with respect to the line period by having one of the rotated cut sections placed before the uncut section and one placed after the uncut section. The cutting point or points are determined by a pseudo random number generator. Receiving apparatus for receiving such an encrypted signal is also disclosed in which a complementary pseudo random number generator is used responsive to receipt of an encryption key to control addressing of a descrambling store in order to reconstitute the original signal.

Abstract: A multiplexed analogue component (MAC) television signal is encrypted for transmission and reception by authorized 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 a 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.