Assessing Video Quality for Public Safety Applications Using Visual Acuity

This report describes a laboratory study investigating the ability of human subjects to use a video system for various tasks. The particular tasks of interest focus on human targets and range from awareness of their presence to positive identification. The test simulates recorded video by allowing viewers significant control over how and when video sequences are displayed. The video sequences represent a variety of target sizes, motion, and lighting conditions. Various resolutions and encoder bit rates were used to allow us, public safety researchers at the Institute for Telecommunication Sciences (ITS), to recommend requirements for a particular task. Test subjects were asked to identify letters on an eye chart synthetically inserted into the video sequences. This allowed us to use visual acuity as a quality metric, which made it possible to separate measurements of the quality required for particular tasks from measurements of quality delivered by particular systems. The task-based subjective tests this report describes follow the test methods described in the International Telecommunication Union’s Telecommunication Standardization Sector (ITU-T) Recommendation P.912.