1. Apparatus for encoding a television signal to be transmitted, comprising: means for sampling a television signal to be encoded; means for selecting sites of samples to be interpolated by one of a plurality of interpolation schemes; means for processing samples neighbouring each sample to be interpolated to evaluate which interpolation scheme applied to the neighbouring samples produces the best value for that interpolated sample; means for generating a descriptor signal adapted, for each sample to be spatially interpolated, to generate a descriptor signal indicative of whether the best spatial interpolation scheme for that sample produces a value greater or less than the average of the values produced by the plurality of spatial interpolation schemes; and means for transmitting the descriptor signals.