The invention refers to an apparatus and a method for reducing random noise in a sequence of digital video frames comprising the following steps: 1. for each of the pixels (center pixel) in a frame a set of adjacent pixels is defined; 2. for each of the adjacent pixels the difference of their values in the current frame and the previous frame is calculated, whereby the value of the center pixel is omitted; 3. each difference value is shifted right for a predefined number of bits; 4. the square of the difference value is added to an activity value of that center pixel; 5. if the activity value remains below a predefined threshold value, then a weighting factor depending from activity value is calculated and 6. the value of the center pixel is set to a weighted value.