Enhancement of inter-frame coded images based on convex projection

Abstract

We propose a degradation model for blocking artifacts in inter-frame coded images and a corresponding image restoration algorithm based on convex projection for reducing blocking artifacts. In contrast to still images, inter-frame coded moving images have two kinds of blocking artifacts. One occurs on the block boundary, which is caused by quantization of block discrete cosine transform (BDCT) coefficients. The other occurs in the interior of the block, which is caused by motion compensation from the previous blocky image. Those properties are used to define convex sets, which specify a priori constraints of the estimated images. In other words, both on the block boundary and in the interior of the block, differential images must have discontinuity in opposite direction to the previous motion compensated image. © 1999 IEEE.