In an interpolation signal producing circuit, amplitudes of a plurality of proximate pixel signals are compared and the order of magnitudes of such pixel signals is determined, whereupon an interpolation signal is derived which is intermediate the largest and smallest amplitudes, for example, next to the largest or smallest amplitudes or an average thereof. The interpolation signal thus derived may be advantageously employed for sub-sampling, that is, doubling the number of pixels in each horizontal scanning line of a displayed video picture, for doubling the horizontal scanning lines in a field, or in compensating for drop-out and the like.