Journal of Broadcast Engineering (방송공학회논문지)

The Korean Institute of Broadcast and Media Engineers (한국방송∙미디어공학회)
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Conditional Probability Based Early Termination of Recursive Coding Unit Structures in HEVC

HEVC의 재귀적 CU 구조에 대한 조건부 확률 기반 고속 탐색 알고리즘

  • Han, Woo-Jin (Dept. of Software Design and Management, Kyungwon University)
  • 한우진 (경원대학교 소프트웨어설계및경영학과)
  • Received : 2011.10.21
  • Accepted : 2012.02.14
  • Published : 2012.03.30
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Abstract

Recently, High Efficiency Video Coding (HEVC) is under development jointly by MPEG and ITU-T for the next international video coding standard. Compared to the previous standards, HEVC supports variety of splitting units, such as coding unit (CU), prediction unit (PU), and transform unit (TU). Among them, it has been known that the recursive quadtree structure of CU can improve the coding efficiency while the encoding complexity is increased significantly. In this paper, a simple conditional probability to predict the early termination condition of recursive unit structure is introduced. The proposed conditional probability is estimated based on Bayes' formula from local statistics of rate-distortion costs in encoder. Experimental results show that the proposed method can reduce the total encoding time by about 32% according to the test configuration while the coding efficiency loss is 0.4%-0.5%. In addition, the encoding time can be reduced by 50% with 0.9% coding efficiency loss when the proposed method was used jointly with HM4.0 early CU termination algorithm.

MPEG과 ITU-T에서 최근 표준화가 진행되고 있는 HEVC는 H.264/AVC에 비해, CU(coding unit), PU(prediction unit), TU(transform unit)의 다양한 형태 분할 단위를 갖는 것을 큰 특징으로 한다. 이 중, CU와 TU는 쿼드트리 형태의 재귀적 분할 구조를 가지도록 구성되는데, 압축 효율은 향상시키지만 높은 부호화 복잡도를 갖는 단점이 있다. 본 논문에서는 이러한 재귀적 분할 구조에서의 rate-distortion cost를 조건부 확률을 이용한 통계적 분석 방법을 사용하여, 분할이 일어나는 경우와 그렇지 않은 경우로 분류하는 방법을 제안한다. 제안한 방법을 HEVC의 재귀적 CU 부호화에 적용한 결과, 부호화 복잡도를 32% 가량 감소시키면서 압축 효율하락은 0.4-0.5%로 억제할 수 있었다. 또한, HM4.0에 구현되어 있는 고속 탐색 알고리즘과 함께 사용하는 경우, 압축 효율 하락을 0.9%로 억제하면서 부호화 복잡도를 1/2로 감소시킬 수 있었다.

Keywords

References

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