대한전자공학회논문지SP (Journal of the Institute of Electronics Engineers of Korea SP)

대한전자공학회 (The Institute of Electronics and Information Engineers)
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POCS와 정규화를 기반으로한 프레임간 압출 영사의 후처리

Postprocessing of Inter-Frame Coded Images Based on Convex Projection and Regularization

  • 김성진 (중앙대학교 첨단영상대학원 영상공학과) ;
  • 정시창 (중앙대학교 첨단영상대학원 영상공학과) ;
  • 황인경 (중앙대학교 첨단영상대학원 영상공학과) ;
  • 백준기 (중앙대학교 첨단영상대학원 영상공학과)
  • Kim, Seong-Jin (Dept.of Media Engineering, Gsaim Art Technology college, Chungang University) ;
  • Jeong, Si-Chang (Dept.of Media Engineering, Gsaim Art Technology college, Chungang University) ;
  • Hwang, In-Gyeong (Dept.of Media Engineering, Gsaim Art Technology college, Chungang University) ;
  • Baek, Jun-Gi (Dept.of Media Engineering, Gsaim Art Technology college, Chungang University)
  • 발행 : 2002.05.01
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초록

본 논문에서는 프레임간 압축된 영상의 블록화 현상을 감소시키기 위해 재구성하기 전 차분 영상을 처리하는 새로운 복원 알고리듬을 제안한다. 프레임내 압축 영상의 블록화 현상은 오직 8×8 DCT에 의해서 일어나는 반면에, 프레임간 압축된 영상에서는 8×8 DCT뿐만 아니라 움직임 보상을 위해 사용한 16×16의 매크로 블록에 의해서 발생된다. 이러한 이유로 본 논문에서는 차분 영상에 대한 새로운 열화모델을 제시하고, 블록 경계와 내부의 불연속에 대한 POCS를 이용한 복원 알고리듬을 제시한다. 제안된 알고리듬은 DCT계수의 일부를 이용해 블록 경계의 방향을 고려하는 공간 적응적 저대역 통과 필터를 포함하는 표준 정규화의 변환된 형태이다. 일반적인 비디오 압축 표준은 블록을 기준으로 하는 움직임 보상과 블록 이산여현 변환(BDCT)을 이용한 혼성(hybrid) 구조를 채택하고 있다. 이러한 이유에서 블록화 현상은 블록 경계와 블록 내부에서 일어난다. 두 종류의 블록화 현상을 좀 더 완벽히 제거하기 위해서 복원된 차분 영상은 블록 경계와 블록 내부에서의 방향성 불연속과 같은 제약조건을 만족시켜야만 한다. 그러한 제약조건은 차분 영상을 복구하기 위한 convex set을 정의하는데 이용한다.

In order to reduce blocking artifacts in inter-frame coded images, we propose a new image restoration algorithm, which directly processes differential images before reconstruction. We note that blocking artifact in inter-frame coded images is caused by both 8$\times$8 DCT and 16$\times$16 macroblock based motion compensation, while that of intra-coded images is caused by 8$\times$8 DCT only. According to the observation, we Propose a new degradation model for differential images and the corresponding restoration algorithm that utilizes additional constraints and convex sets for discontinuity inside blocks. The proposed restoration algorithm is a modified version of standard regularization that incorporate!; spatially adaptive lowpass filtering with consideration of edge directions by utilizing a part of DCT coefficients. Most of video coding standard adopt a hybrid structure of block-based motion compensation and block discrete cosine transform (BDCT). By this reason, blocking artifacts are occurred on both block boundary and block interior For more complete removal of both kinds of blocking artifacts, the restored differential image must satisfy two constraints, such as, directional discontinuities on block boundary and block interior Those constraints have been used for defining convex sets for restoring differential images.

키워드

참고문헌

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