Arthur A. Webster et al.

Abstract: The Institute for Telecommunication Sciences (ITS) has developed an objective video quality assessment system that emulates human perception. The system returns results that agree closely with quality judgements made by a large panel of viewers. Such a system is valuable because it provides broadcasters, video engineers and standards organizations with the capability for making meaningful video quality evaluations without convening viewer panels. The issue is timely because compressed digital video systems present new quality measurement questions that are largely unanswered. The perception-based system was developed and tested for a broad range of scenes and video technologies. The 36 test scenes contained widely varying amounts of spatial and temporal information. The 27 impairments included digital video compression systems operating at line rates from 56 kbits/sec to 45 Mbits/sec with controlled error rates, NTSC encode/decode cycles, VHS and S-VHS record/play cycles, and VHF transmission. Subjective viewer ratings of the video quality were gathered in the ITS subjective viewing laboratory that conforms to CCIR Recommendation 500-3. Objective measures of video quality were extracted from the digitally sampled video. These objective measurements are designed to quantify the spatial and temporal distortions perceived by the viewer. This paper presents the following: a detailed description of several of the best ITS objective measurements, a perception-based model that predicts subjective ratings from these objective measurements, and a demonstration of the correlation between the model's predictions and viewer panel ratings. A personal computer-based system is being developed that will implement these objective video quality measurements in real time. These video quality measures are being considered for inclusion in the Digital Video Teleconferencing Performance Standard by the American National Standards Institute (ANSI) Accredited Standards Committee T1, Working Group T1A1.5.

Keywords: objective video quality assessment; subjective video quality assessment

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