Patent US 4,237,484

Supplementary digital data is encoded together with a video signal by predicting the intensity values of a first set of video samples, compressing the range of the prediction errors and superimposing a value indicative of the supplementary data on the compressed value. The samples in the first set may be selected in a regular sequence or asynchronously in accordance with a function of the video signal such as the slope in the area of the picture being processed; the composite values are time multiplexed with the remaining intensity values.