A Simplified Approach to Reduce Blocking and Ringing Artifacts in Transform-Coded Images
Jianping Hu · 2000
Presently Block-based Discrete Cosine Transform (BDCT) image coding techniques are widely used in image and video compression applications such as JPEG and MPEG. At a moderate bit rate, BDCT is usually a quite satisfactory solution to most of practical coding applications. However, for high rate compression it produces noticeable blocking and ringing artifacts in the decompressed image. It has been an active research area for a decade for reducing these artifacts. In this thesis, a novel post-processing algorithm is proposed to remove the blocking and ringing artifacts at low bit rate. It is non-iterative and uses both spatial and transform domain approaches. The main steps in this algorithm include block classification, boundary low-pass filtering and mid-point interpolation, edge detection and region merge, and DCT coefficient constraint. The improvement is demonstrated both subjectively and objectively. The extension from .still images to video is also discussed at the end.