Contour restoration apparatus

摘要

A contour restoration apparatus has a plurality of delay circuits connected in series. Maximum and minimum value detection circuits detect maximum and minimum values among an input video signal and output signals of the delay circuits. A mean value circuit is used to calculate a mean value of the of the maximum and minimum values. The mean value is subtracted from a delayed signal having a delay time of one-half of a delay time obtained from all the delay circuits. An adder is used to add the result of the subtraction to the delayed signal. A non-linear processing circuit processes the output of said adder and the maximum and minimum values. The non-linear circuit outputs the output signal of the adder, if the output signal of said adder is between the maximum value and the minimum value. A contour extraction circuit multiplies a signal located centrally among the input video signal, the output signals and the signals located before and after the input signal with a predetermined coefficient. An adder adds the multiplied signals. Another adder adds the result of multiplied signal and the centrally located signal. A contour amplitude circuit detects a difference between the maximum and minimum values and outputs a coefficient determined according to the difference detected. A mixer mixes the output of the non-linear processing circuit and the output of the another adder.