<title>Perceptual distortion measure for edgelike artifacts in image sequences</title>

Abstract

This paper presents an objective perceptual distortion measure quantifying the visibility of edge-like blocking artifacts in coded image sequences resulting from popular transform coding techniques. The prime motivation for this work is the awareness that properties of the human visual system should be central to the design and evaluation of image coding algorithms. The perceptual metric is the output of a visual model incorporating both the spatial and temporal characteristics of the visual system. Parameters of the model are based on results from a number of visual experiments in which sensitivities to simulated blocking artifacts were measured under various spatio-temporal background conditions. The visual model takes a pair of original and distorted sequences as inputs. Distortions are calculated along the vertical and horizontal directions. Visibility dependencies on spatial, temporal and motion activities of the background are incorporated using linear filtering and motion estimation. Pixel-based distortions are combined over local spatial and temporal regions to generate an overall distortion measure for each orientation. The final model output is the sum of the vertical and horizontal distortion measures. The model was applied to coded image sequences and the resulting distortion measures were compared to outcomes of subjective ranking tests. Results indicate that the perceptual distortion measure agrees well with human evaluation.