Improved POCS-Based De-blocking Algorithm for Block-Transform Compressed Images

This paper presents a postprocessing technique based on the theory of projections onto convex sets (POCS) to reduce the blocking artifacts in low bit rate BDCT-coded images. In the block discrete cosine transform (BDCT), the image is divided into a grid of non-overlapped 8 × 8 blocks, and then each block is coded separately. Thus, a block, which is shifted one pixel diagonally from the original grid of BDCT, will include the boundary of the original 8 × 8 block. If blocking artifacts are introduced along the block boundary, the frequency characteristics of this shifted block will be different from those of the original block. Therefore, a comparison of frequency characteristics of these two overlapping blocks can detect the undesired high-frequency components, mainly caused by the blocking artifacts. By eliminating these undesired high-frequency components adaptively considering the local statistical properties of the image, robust smoothing projection operator can be obtained. Comp...

• Type: Conference
• Year: 2003
• Where: ISCIS
• Authors: Yoon Kim, Chun-Su Park, Kyunghun Jang, Sung-Jea Ko
• Keywords: Block Discrete Cosine, Frequency Characteristics, ISCIS 2003, Original Block