Low-complexity post-processing for artifact reduction in block-DCT based video coding

Most widespread video coding algorithms (such as MPEG, H.261, H.263) employ DCT coding for data compression but introduce annoying artefacts due mainly to the independent quantization of the coefficients in each block, that are especially visible at medium and low bitrates. Within this framework, post-processing appears to be a practical solution for visual enhancement of compressed video. In this paper, an adaptive anisotropic spatial-variant FIR filtering procedure is proposed. The filter kernels are selected on the basis of a pixel classification procedure that performs a block-DCT coefficients energy analysis and an edge extraction. The analysis of the transform coefficients matrix allows one to extract information about spatial characteristics, while the edge information provide the basis for the estimation of the position of the local visual artifact. Accurate filtering results were obtained during experiments that outperform those obtained with other existing approaches.