Application of a visual model to the design of an ultra-high definition upscaler

摘要

A Visual Model (VM) is used to aid in the design of an Ultra-high Definition (UHD) upscaling algorithm that renders High Definition legacy content on a UHD display. The costly development of such algorithms is due, in part, to the time spent subjectively evaluating the adjustment of algorithm structural variations and parameters. The VM provides an image map that gives feedback to the design engineer about visual differences between algorithm variations, or about whether a costly algorithm improvement will be visible at expected viewing distances. Such visual feedback reduces the need for subjective evaluation. This paper presents the results of experimentally verifying the VM against subjective tests of visibility improvement versus viewing distance for three upscaling algorithms. Observers evaluated image differences for upscaled versions of high-resolution stills and HD (Blu-ray) images, viewing a reference and test image, and controlled a linear blending weight to determine the image discrimination threshold. The required thresholds vs. viewing distance varied as expected, with larger amounts of the test image required at further distances. We verify the VM by comparison of predicted discrimination thresholds versus the subjective data. After verification, VM visible difference maps are presented to illustrate the practical use of the VM during design.