Removal of DCT blocking artifacts using DC and AC filtering

This paper introduces a post-filtering algorithm that reduces the blocking artifacts caused by quantizing to zero the high frequency DCT coefficients. First, the algorithm detects the blocks that only have a DC coefficient. Second, the blocking artifacts are reduced by averaging the DC coefficient of the block in question and the DC coefficients of the neighboring four 8×8 DCT blocks. These blocking artifacts are further reduced by predicting the low-frequency AC coefficients from the DC coefficient within a 3×3 array of blocks. Experimental results show that averaging the DC coefficients and predicting the low frequency AC coefficients definitely help to remove blocking artifacts in smooth background areas of the image.