画質の主観評価における眼球運動の分析

Abstract

This paper analyzes the ways eye movements are affected by some factors : the impairment magnitudes, the picture contents, different kinds of assessors, subjective evaluation methods, different types of impairment. Hi-Vision picture quality, degraded by the bandwidth limitation and the addition of the white noise, is evaluated using the SSQS (Single-Stimulus Quality Scale) method and the EBU method (officially, Double-Stimulus Impairment Scale method). First, it is shown that the subjective evaluation method affects the absolute objective measure (total fixation duration, number of fixation points, moving distance between fixation points), the ratio of total fixation duration to judgment duration, and the objective measure concerning the moving distance. Next, the ratio of fixation duration in each region, divided by the contents of the test pictures, to total fixation durations is analyzed, and the validity of the description in the ITU-R Rec. 500-6, such that the SSQS method is suitable for evaluating the overall picture quality and the EBU method is suitable for evaluating small impairments, is confirmed. Finally, examined is whether the stability of evaluation is connected with any objective measure regarding the eye movements, the fixation duration ratio in each region divided by the picture contents, and the fixation duration distribution. Consequently, it is shown that the assessor's ability to discriminate picture quality is connected with the fixation duration ratio in each region divided by the picture contents and the fixation duration distribution.