System for reducing beat type impairments in a tv signal

Abstract

The system for reducing composite beat, composite second order beat and thermal (snow) noise impairments in a television system digitizes individual frames to apply digitized a grey scale values (v.sub.(i,j)) to the pixels in the frames and then applying a spatial filter to a block of pixels including the then current pixel being processed to determine the pixel (P.sub.(min)) with the minimum grey scale value (v.sub.(min)) and the pixel (P.sub.(max)) in the block with the maximum grey scale value (v.sub.(min)). V.sub.(max) -v.sub.min is compared with a threshold value (v.sub.(T)) and if v.sub.(max) -v.sub.min) >v.sub.(T), the value (v.sub.(i,j)) of the pixel being processed remains unchanged, but if v.sub.(max)-v.sub.(min).notgreaterthan.v.sub.(T), a value (v.sub.(av.)) equal to the weighted average value of pixels in the block is used as the grey scale value v.sub.(R-i,j) for the pixel being processed. The block preferably, will be composed of a number of adjacent pixels in a row or a number of adjacent pixels in a column or both processed simultaneously or preferably in sequence i.e. the pixels processed along the rows and then along the columns with the values assigned to the pixels when processing along the rows used as the initial values for the pixels when processing along the columns. In more preferred cases, a plurality of frames are each subject to static filtering and then the adjacent frames in the sequence are subject to time filtering (provided motion is not detected) to provide a better average value vZ.sub.(mean) for the processed pixel in the specific frame being processed.