Patent ID: 6983079

Claim:
A method for reducing artifacts in digital data, comprising the steps of: (a) obtaining a reconstructed block-based pixel representation of the digital data; (b) extracting a DC coefficient for each block in the pixel representation based on values of selected pixels in that block to generate a map of DC coefficients; (c) for each pixel block, predicting a select number of lower frequency AC coefficients using the DC coefficient for that pixel block and a select number of neighboring DC coefficients in the DC coefficient map to construct a corresponding partial transform-coefficient block; (d) classifying each pixel block as a low-activity block or a high-activity block based on the predicted AC coefficients in the corresponding partial transform-coefficient block; and (e) selectively performing a low-pass filtering operation on select pixels in select pixel blocks on a block-by-block basis based on the classification of that block, the locations and values of predicted non-zero AC coefficients in the corresponding partial transform block, and certain pixel values in that block, wherein a low-pass filter of a first strength is applied to a given pixel region in a given low-activity block if a minimum condition for that pixel region is satisfied, and wherein a low-pass filter of a second strength is applied to a given pixel region in a given high-activity block if a minimum condition for that pixel region is satisfied.