Patent ID: 8184721

Claim:
A method of recursive filtering of a video image comprising: a. storing, using a computer system, an image to comprise stored picture elements S(x,y); b. providing, using the computer system, luminance and chrominance weightings for weighting neighbouring picture elements to a picture element to be processed; c. calculating, using the computer system, a sum σ(x,y) of differences between luminance and chrominance values of a picture element C(x,y) and neighbouring picture elements of a current image and of corresponding picture elements S(x,y) of the stored image, weighted by the luminance and chrominance weightings, wherein the sum of differences is calculated using the equation: σ ⁡ ( x , y ) = ∑ m = - 2 2 ⁢ ∑ n = - 2 2 ⁢ W luma ⁡ ( m , n ) · ABS ⁡ ( C luma ⁡ ( x + m , y + n ) - ⁢ S luma ⁡ ( x + m , y + n ) ) + α · W chroma ⁡ ( m , n ) ⁢ ABS ⁡ ( C chroma ⁡ ( x + m , y + n ) - ⁢ S chroma ( x + m , y + n ⁢ ) ) where: m and n are offsets in the x and y directions respectively over which neighbouring picture elements are taken into account, W luma (m,n) and W chroma (m,n) are the luminance and chrominance weightings respectively applied to the picture element and neighbouring picture elements over a range m=−2 to +2 and n=−2 to +2, C(x,y) is the luminance and chrominance values of the (x,y) picture element of the current image, and S(x,y) is the luminance and chrominance values of the (x,y) picture element of the stored image; d. normalizing, using the computer system, the sum of absolute differences with a normalising coefficient λ to control sensitivity to motion to form a proportional parameter K(x,y)=λσ(x,y); e. recursively filtering, using the computer system, the image using a value of the proportional parameter K(x,y) corresponding to each picture element by adding together a proportion K(x,y) of each picture element C(x,y) of the image to a complementary proportion 1−K(x,y) of each corresponding picture element S(x,y) of the previously stored image.