A method for contour reduction in a digital picture is disclosed. The method generally includes the steps of (A) buffering a plurality of luma samples in a current line of the digital picture, each of the luma samples having a respective input value, (B) calculating a plurality of horizontal sum-of-signs along the current line, wherein each of the horizontal sum-of-signs comprises a sum of a plurality of amplitude differences between pairs the luma samples from the current line and (C) generating a plurality of output value based on the horizontal sum-of-signs, one of the output values for each one of the luma samples.