Does H.265 based peri and para-foveal quality flicker disrupt natural viewing patterns?
Region of interest based coders and also those coders that extensively use the Intra coding mode tend to produce flickering artefacts due to the inherent quality fluctuations they produce in the non-salient or homogeneously textured intra coded regions of a scene respectively. These non-salient areas are in turn incident on the para, peri and extra-peri foveal retinal regions that are especially sensitive to temporal artefacts. To study the perceptual effects of such a quality based flicker in the retinal periphery, in this experiment gaze data was collected from 48 observers in a free viewing scenario using a regulated flicker stimulus. The video stimulus in the mentioned peripheral regions were flickered with a predetermined frequency and amplitude by adaptively combining the streams produced using a H.265 video coder, and presenting them in a Gaze Contingent Display(GCD) setup. Utilizing statistical gaze analysis techniques, we observe that, temporal quality flicker in the visual periphery plays a major role in disturbing the natural viewing patterns of an observer. Further, this effect was found to be maximum in the 7.5Hz temporal band thus showing that, encoders that affect temporal quality smoothness must aim to avoid such distraction effects.