Post processing for blocking artifact reduction

Since current coding standards rely on block based processing, reconstructed images include horizontal and vertical grid noise along the block boundaries. This image degradation, called blocking artifacts, is mainly caused due to the quantization process of discrete cosine transform (DCT) coefficients. In this paper, we present a novel post processing framework for blocking artifact reduction, which is based on the correction of a few quantized DCT coefficients. We first smooth inter-block DCT coefficients for the three lowest frequency (LF) ones, in order to reduce blocking artifacts in the flat region which are most sensitive to the human visual system (HVS). We then apply block based 3-D filtering to the edge region to reduce the remaining artifacts. Experimental results show that the proposed method successfully alleviates blocking artifacts in the images coded with low bit-rates.