Method and apparatus for noise reduction.

摘要

Different kinds of video noise filters are known. Normally such filters need a certain amount of memory, e.g. field memories, or are not suited for every noise level or are not adaptive to the local structure of the picture. The inventive solution is globally and locally adaptive. A noisy input signal x is filtered with a restoration filter of median type to generate a filtered input signal y. The sum of the absolute differences between filtered and unfiltered signal is calculated for each position of a sliding window within the input signal, representing a local estimate of the noise, and is combined with a global measure of the input signal noise to compute two coefficients a and b which are respectively applied to the unfiltered and filtered signal to generate the output signal z = a*x + b*y. Advantageously different kind of filters operate in parallel, whereby the kind of filter elected is locally adapted to the picture activity. <IMAGE>