A Framework of Perceptual Quality Assessment on LCD-TV

Transcription

1 A Framework of Perceptual Quality Assessment on LCD-TV Journal of Displays Vol. 28, No. 1, 2008 Wen-Hung Kuo, Po-Hung Lin, and Sheue-Ling Hwang Presented by Euiwon Nam School of Electrical Engineering and Computer Science Kyungpook National Univ.

2 Evaluation framework Abstract Perceptual quality on liquid crystal display-television (LCD-TV) Analytical hierarchy process(ahp) Relationship between subjective assessment and physical measurement Providing useful information for improvement of industry Important factors for quality of LCD-TV 2/26

3 Video display unit(vdu) Introduction Cathode ray tube(crt) Liquid crystal display(lcd) monitors Smaller, lighter, lower power Plasma display panel (PDP) Digital light processing (DLP) liquid crystal on silicon (LCoS) 3/26

4 Image quality assessment of television Nishizawa Comparison of picture quality between CRT-TVs and LCD-TVs Contrast ratio, viewing angle, response speed, and color reproduction Heynderickx and Langendijk Comparison of image with PDP, LCD, CRT, and LCoS Projection Color rendering, brightness, contrast, display function, ambient illumination, sharpness, and artifact Rajae-Joordens and heynderickx Depth impression and overall image quality for 2D-TV Resolution, sharpness, contrast, and luminance 4/26

5 Image quality assessment of human perception Display quality measurement User s point of view Besuijen and Spenkelink Bech Evaluation of essential factor in display quality measurement Development of RaPID(Rapid Perceptual Image Description) Nyman Hybrid, qualitative/quantitative measurement Rajae-Joordens and Engel Perceived difference in field of visual perception experiment Applied to translate paired comparison data Heynderickx and Langendijk» PDP, LCD, CRT, and LCoS projection 5/26

6 Satty Analytical hierarchy process(ahp) for subjective measurement One of the popular and powerful methods for decision-making Analytical hierarchy process(ahp) Development of intelligent material handling equipment selection system Chan Selection of most appropriate tool to support knowledge management Ngai and Chan 6/26

7 Proposed method Evaluation framework based on investigation of five LCD-TVs Important factors for affection of video or images quality Comparison between subjective assessment and physical measurement Improvement of quality of LCD-TVs Suitable LCD-TVs for consumer as user 7/26

8 Evaluation framework Three stage for evaluation frame Obtaining ordinary users feelings or knowledge Requirements of high quality LCD-TV Analytical hierarchy process(ahp) subjective assessment of important factors Physical measurements by instruments 8/26

9 Framework of proposed Fig. 1. Evaluation framework of LCD-TV perceptual quality assessment. 9/26

10 Evaluation experiment Composition of experiment Subjects; age(mean 27.2 and SD 2.28) Experimental LCD-TVs and test patterns BenQ DV3250, Polyview NLC30C2, Sampo LM-32HX, Sumsung LT- P326W, and Sharp LC- 30HV6U Fig. 2. Five LCD-TVs prepared in the experiment. 10/26

11 Test patterns Two still images and one motion picture Eight factors Table 1. Eight factors considered in experiment (a) (b) (c) Fig. 3. (a) and (b) are two still images from ISO 12640; (c) is motion picture from movie Mulan. 11/26

12 Instrumental measurements Notebook and displayed on LCD-TVs Fig. 4. Set-up for measuring static image quality. 12/26

13 Test pattern Contrast and luminance (a) (b) Fig. 5. (a)test pattern for contrast and (b) is test pattern for luminance. 13/26

14 Calculating signal change of LCD-TVs from oscilloscope (a) (b) Fig. 6. Set-up for measuring moving image quality. 14/26

15 Evaluation process General feeling or requirement from ordinary user s point of view Suitable adjectives for high quality LCD-TV Specifications or functions for high quality LCD-TV.» Color, response, viewing component Subjective assessment based on AHP method Evaluation of image quality of LCD-TV Explanation of eight factors» Score for importance of factors Table 4. Rotated component matrix with Varimax rotation method 15/26

16 Construction of four-level AHP model Fig. 7. Set-up for measuring moving image quality. 16/26

17 physical measurements of some measurable factors Comparison for each factor» Subjective assessment (second stage)» physical measurement (third stage) 17/26

18 Results and discussion The results through questionnaire Results of first stage Table 2. Rank of factors from the questionnaire Table 3. Rank of adjectives from the questionnaire 18/26

19 The results from AHP Judging importance of factor Weight of factor where in m W ( c e ) m n in in i 1 n is importance of factor. c and e in are local priorities of corresponding elements of factor n in second and third levels obtained from subject i ( i 1,..., m). (1) Example for weight of luminance based on image 1 10 W ( c e ) 10 lum i, lum i, lum i 1 (2) where c e i, lum i, lum is local priority of color component in second level. is local priority of luminance in third level obtained from subject i 19/26

20 » Result of example Table 5. Local priority of luminance in still image 1 20/26

21 Result for eight factor Still image and motion picture Table 6. Weight of eight factors in the still images Table 7. weight of eight factors in the motion picture 21/26

22 Judging importance of factor Weight of factor on LCD-TV m k k m n in in in i 1 W c e l (3) k where l is local priority of factor n on LCD-TV ( k) in fourth level obtained in from subject i ( i 1,..., m). Table 8. Weight of eight factors on each LCD-TV 22/26

23 Obtaining rank of these LCD-TVs Global weight m k k W m cin ein lin n i 1 (4) k where l is local priority of factor n on LCD-TV ( k) in fourth level obtained in from subject i ( i 1,..., m). 23/26

24 ANOVA of different scenarios Investigation of subjective assessment of three scenarios Comparison between questionnaire s and AHP s results Three common important factors Contrast, luminance, and response time Table 9. ANOVA table of different scenarios 24/26

25 Comparison between physical measurement and AHP result Table 10. Comparison of measurements and weights of AHP 25/26

26 Evaluation framework Conclusion Perceptual quality assessment Common user s feeling or knowledge from the questionnaire Subjective assessments from AHP Physical measurements by instruments Found Importance factor for quality of LCD-TV Most important quality factors Contrast, luminance, and response time Most differentiable factor Sharpness 26/26