A Comparative Study of Compensation Techniques in Directional DCT's
Jingjing Fu, Bing Zeng · 2007
A block-based directional DCT framework has been developed recently in which the first transform may choose to follow a direction other than the vertical or horizontal one – the default direction in the conventional 2D DCT, while the second transform is selected according to the first one. However, these directional DCT's would suffer from the so-called mean weighting defect because DCT's of different lengths have to be used at the first step along different directional lines within each image block, thus resulting in some unnecessary non-zero components during the second transform. This paper presents a comparative study of various techniques for compensating such defect, including different ways of modifying the scaling factors used in the DCT matrices and the so-called ΔDC correction method. These techniques are compared with each other in terms of coding performance and computational complexity.