Cj. Kuo et Rj. Hsieh, ADAPTIVE POSTPROCESSOR FOR BLOCK ENCODED IMAGES, IEEE transactions on circuits and systems for video technology, 5(4), 1995, pp. 298-304
Blocking effects are a major degradation in block based image coding t
echniques, In this paper, we propose an adaptive postprocessor for the
removal of blocking effects. The adaptation is achieved by changing f
ilter coefficients according to the local characteristics of images an
d the blocking effects. Here, a space-variant lowpass filter is used t
o smooth the pixels at block boundaries where the blocking effects are
highly visible, In addition, the pixels that are closed to an edge ar
e adaptively regional or directional lowpass filtered if the blocking
effects are obvious, As for the pixels at edges, they are left untouch
ed by the postprocessor. Therefore, blocking effects can be removed wi
thout blurring the edge sharpness. Performance improvements compared w
ith other techniques are obtained according to simulation results. The
proposed postprocessor has el dB gain (depending on the images) compa
red with the loop filter of H.261 [1], the linear filter [2], and the
nonlinear space-variant postprocessor [3].