Method and apparatus for removing noise artifacts in decompressed video signals

Abstract

A method of and circuitry for removing noise artifacts in decompressed video signals. A group of pixels is selected from a larger matrix of pixels from adjacent rows and columns of the matrix. A plurality of different subgroups of the group of pixels is selected, each subgroup including the same centrally located pixel. The maximum energy intensity difference emanating from each pixel in each of the subgroups is measured and the maximum difference among the pixels in each subgroup is determined. The subgroup having the lowest maximum difference is selected and the weighed mean of the selected pixels in the subgroup is computed with weights chosen to provide more significance to pixels which are located closer to the centrally located pixel. The centrally located pixel is then filtered with a linear filter, the coefficients of which are determined by the sum of absolute differences between the weighed mean and the pixels in the subgroup. Output from this linear filter is then conditionally filtered by linear filters of fixed coefficients in the vertical and horizontal directions to provide the final filtered version of the centrally located pixel. The subgroups include an odd number of rows and columns. The subgroups preferably include a first and second subgroups extending along each diagonal, a third subgroup extending along a single column and each of the rows, a fourth subgroup extending along a single row and each of the columns and a fifth subgroup surrounding the centrally located pixel.