A Psychophysical Study Exploring Judder Using Fundamental Signals and Complex Imagery

Abstract

There are well-known observations of movie content being displayed at different frame rates. Although the terms are not consistent across the industry, four main degradations are observed of the signal as compared to nonsampled motion (i.e., real-world motion): (1) nonsmooth motion, (2) false multiple edges, (3) flickering, and (4) motion blur. In natural imagery, all four of these effects are generally visible at typical movie frame rates. The spatiotemporal window of visibility has proved successful in describing when motion looks distorted from the real-world smooth motion. However, that model predicts only detection performance and does not address the appearance or magnitude of motion distortions. In addition, well-known image capture and display parameters are also involved with frame rate questions, such as exposure duty cycle (angle), object speed, and object contrast. There are also known interactions with brightness and contrast, which are also generally linked in the end-to-end system. For example, the Ferry-Porter law1 of psychophysics indicates the temporal frequency bandwidth of vision increases with increasing adapting luminance. We aimed to isolate the nonsmooth motion component of judder in a psychophysical study by using fundamental test signals, such as the Gabor signal. Two-interval forced choice methodology was used to generate interval scales of the magnitude of judder, or judderness. Results are presented for the viewer assessment of the magnitude of judder/judderness as a function of these key parameters tested in isolation.