1. A motion compensation deinterlacer for producing a progressive scan signal from an interlaced signal comprising: (a) a motion compensation means for deriving missing lines in an interlaced field from at least one other field in the interlaced signal; (b) means for deriving a first confidence measure for the accuracy of the motion compensation means using the known lines of the field for which missing lines are to be derived; (c) means for deriving a second confidence measure for the accuracy of the motion compensation unit using known lines of at least two other fields; and, (d) means for selecting outputs for display from at least the motion compensation unit and one other deinterlacing means in dependence on the result of the comparison.