새로운 광적응 효과 모델을 이용한 정교한 영상 화질 측정

국문 초록 (Abstract)

인간 시각 체계(Human Visual System: HVS)의 영상 화질 인지 특성을 정교하게 반영하는 객관적 영상 화질 측정(Image Quality
Assessment: IQA)방법들이 최근 활발히 연구되어 왔다. 이와 관련된 HVS의 특성 중, 광적응(Luminance Adaptation: LA)효과는 HVS의 왜곡에 대한 민감도가 영상 배경 밝기에 따라 달라지는 특성을 가리키며, 이 효과는 베버의 법칙(Weber’s law) 모델을 통해 많은 IQA 방법들에 반영되어져 왔다. 본 논문에서는 처음으로 이러한 베버의 법칙 모델을 기반으로 하는 기존 IQA 방법들이 LA 효과를 부정확하게 반영해 왔다는 점을 수학적/정신물리학적 분석을 통해 밝힌다. 이러한 분석을 기반으로 우리는 IQA 방법에 LA 효과가 정교하게 적용될 수 있는 새로운 LA 효과 기반 국부 가중치 함수(LA effect-based Local weight Function: LALF)를 제안한다. 우리는 제안 LALF를 SSIM(Structural SIMilarity) 및 PSNR 척도(metric)에 적용하여 제안 방법의 효과를 검증하였다. 실험 결과, LALF가 적용된 SSIM은 기존 SSIM 대비 측정된 주관적 화질 점수와의 스피어 랭크 순위 상관계수 기준 약 5% 포인트가 향상될 정도로 제안방법의 큰 효과성을 입증하였다. 또한, 제안한 LALF는 PSNR에 적용된 경우에도 기존 PSNR 대비 약 2.5% 포인트의 성능 향상을 보였다.

다국어 초록 (Multilingual Abstract)

Recently, objective image quality assessment (IQA) methods that elaborately reflect the visual quality perception characteristics of human visual system (HVS) have actively been studied. Among those characteristics of HVS, luminance adaptation (LA) effect, indicating that HVS has different sensitivities depending on background luminance values to distortions, has widely been reflected into many existing IQA methods via Weber’s law model. In this paper, we firstly reveal that the LA effect based on Weber’s law model has inaccurately been reflected into the conventional IQA methods. To solve this problem, we firstly derive a new LA effect-based Local weight Function (LALF) that can elaborately reflect LA effect into IQA methods. We validate the effectiveness of our proposed LALF by applying LALF into SSIM (Structural SIMilarity) and PSNR methods. Experimental results show that the SSIM based on LALF yields remarkable performance improvement of 5% points compared to the original SSIM in terms of Spear rank order correlation coefficient between estimated visual quality values and measured subjective visual quality scores. Moreover, the PSNR (Peak to Signal Noise Ratio) based on LALF yields performance improvement of 2.5% points compared to the original PSNR.

목차 (Table of Contents)

• 요약
• Abstract
• Ⅰ. 서론
• Ⅱ. 관련 연구
• Ⅲ. 정교한 FR-IQA 방법을 위한 LA 효과 모델 제안
• Ⅳ. 실험 결과
• Ⅴ. 결론
• 참고문헌(References)

참고문헌 (Reference)

• 1 N. Ponomarenko, "TID2008-A database for evaluation of full-reference visual quality assessment metrics" 10 : 30-45, 2009
• 2 Z. Wei, "Spatio-temporal just noticeable distortion profile for grey scale image/video in DCT domain" 19 (19): 337-346, 2009
• 3 J.-S. Choi, "Single image super-resolution based on self-examples using context-dependent subpatches" 2015
• 4 Z. Wang, "Multiscale structural similarity for image quality assessment" 1398-1402, 2003
• 5 Z. Wang, "Mean squared error: Love it or leave it? A new look at signal fidelity measures" 26 (26): 98-117, 2009
• 6 Z. Wang, "Information content weighting for perceptual image quality assessment" 20 (20): 1185-1198, 2011
• 7 Z. Wang, "Image quality assessment: from error visibility to structural similarity" 13 : 600-612, 2004
• 8 "Final Report From the Video Quality Experts Group on the Validation of Objective Models of Video Quality Assessment VQEG"
• 9 S.-H. Bae, "Assessments of subjective video quality on HEVC-encoded 4K-UHD video for beyond-HDTV broadcasting services" 59 (59): 209-222, 2013
• 10 J. Kim, "An HEVC-compliant perceptual video coding scheme based on JND models for variable block-sized transform kernels" IEEE Trans. Circuits Syst. Video Technol 2014
• 11 C.-H. Chou, "A perceptually tuned subband image coder based on the measure of just-noticeable distortion profile" 5 (5): 467-476, 1995
• 12 S.-H. Bae, "A novel image quality assessment based on an adaptive feature for image characteristics and distortion types" 2015
• 13 S.-H Bae, "A novel generalized DCT-based JND profile based on an elaborate CM-JND model for variable block-sized transforms in monochrome images" 23 (23): 2014
• 14 S.-H Bae, "A novel DCT-based JND model for luminance adaptation effect in DCT frequency" 20 (20): 893-896, 2013
• 15 J.-S. Choi, "A no-reference perceptual blurriness metric based fast super-resolution of still pictures using sparse representation" 9401 : 94010-94011, 2015
• 16 S.-H. Bae, "A new DCT-based JND model of monochrome images for contrast masking effects with texture complexity and frequency" 431-434, 2013
• 17 T. Frese, "A methodology for designing image similarity metrics based on human visual system models" 3016 : 472-483, 1997
• 18 L. Zhang, "A comprehensive evaluation of full reference image quality assessment algorithms" 1477-1480, 2012