전자공학회논문지 (Journal of the Institute of Electronics and Information Engineers)

대한전자공학회 (The Institute of Electronics and Information Engineers)
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급격한 조명 변화에 강건한 동영상 대조비 개선 방법

Robust Method of Video Contrast Enhancement for Sudden Illumination Changes

  • 박진욱 (한양대학교 컴퓨터공학과) ;
  • 문영식 (한양대학교 컴퓨터공학과)
  • Park, Jin Wook (Department of Computer Science and Engineering Hanyang University) ;
  • Moon, Young Shik (Department of Computer Science and Engineering Hanyang University)
  • 투고 : 2015.08.18
  • 심사 : 2015.10.28
  • 발행 : 2015.11.25
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초록

동영상 대조비 개선 과정에서 단일 영상을 위해 연구된 대조비 개선 방법들을 사용할 수 있지만, 동영상의 연속성이 고려되지 않으면 원본 동영상에 없는 깜박임을 야기할 수 있다. 또한 동영상의 연속성을 고려하는 경우, 깜박임은 억제할 수 있지만 연속성 때문에 조명의 급격한 변화할 때 불필요한 페이드인/아웃(fade-in/out) 현상이 발생하는 단점이 발생할 수 있다. 본 논문에서는 깜박임과 페이드인/아웃 현상 없이 동영상의 대조비를 개선하는 방법을 제안한다. 제안하는 방법은 Fast Gray-Level Grouping(FGLG)를 사용하여 각 프레임의 대조비를 개선하고, 깜박임을 억제하기 위해 Exponential smoothing 필터를 사용한다. 불필요한 페이드인/아웃 현상을 억제하기 위해서는 S형 함수로 Exponential smoothing 필터의 평활화 비율을 프레임 별로 적응적으로 계산하여 적용한다. 실험에서 제안하는 방법과 기존의 방법들은 6가지 측정 기준을 적용하여 성능을 비교 및 분석한다. 실험 결과, 제안하는 방법은 영상 형태 보존을 측정하는 MSSIM과 깜박임을 측정하는 Flickering score에서 정량적으로 가장 높은 결과를 보여주었으며, 시각적인 품질 비교를 통해 조명 변화에 따른 적응적인 개선을 정성적 결과로 입증하였다.

Contrast enhancement methods for a single image applied to videos may cause flickering artifacts because these methods do not consider continuity of videos. On the other hands, methods considering the continuity of videos can reduce flickering artifacts but it may cause unnecessary fade-in/out artifacts when the intensity of videos changes abruptly. In this paper, we propose a robust method of video contrast enhancement for sudden illumination changes. The proposed method enhances each frame by Fast Gray-Level Grouping(FGLG) and considers the continuity of videos by an exponential smoothing filter. The proposed method calculates the smoothing factor of an exponential smoothing filter using a sigmoid function and applies to each frame to reduce unnecessary fade-in/out effects. In the experiment, 6 measurements are used for the performance analysis of the proposed method and traditional methods. Through the experiment. it has been shown that the proposed method demonstrates the best quantitative performance of MSSIM and Flickering score and show the adaptive enhancement under sudden illumination change through the visual quality comparison.

키워드

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