Low-Resolution TV: Subjective Comparison of Interlaced and Noninterlaced Pictures

Abstract

A subjective comparison of line-interlaced television pictures and noninterlaced television pictures has shown that the line-interlacing of low-resolution television pictures provides a bandwidth saving of considerably less than 2:1 when the line structure of the picture is visible. A line-interlaced television picture was subjectively compared with several noninterlaced television pictures in an effort to determine their subjective equivalency in terms of bandwidth. Several other variables — noise, spot-wobble, line-width to line-pitch ratio, different models, illumination and luminance — were also employed in the experiments. The televised pictures consisted of a head-and-shoulder view of a model pantomiming a two-way conversation. The results indicate that the line-interlacing of low-resolution television pictures provides about a 37 percent saving in terms of bandwidth at a relatively low value of high-light luminance of 40 fL (140 cd/m2) and as little as a 6 percent savings at a high-light luminance of 100 fL (340 cd/m2). When the line-width to line-pitch ratio is set at its preferred value for all pictures, a significant difference is obtained when the high-light luminance is decreased from 60 fL (200 cd/m2) to 40 fL (140 cd/m2). The effects of Gaussian noise, spot-wobble, illumination, and different types of models did not alter the subjective equivalence of line-interlaced and noninterlaced television pictures significantly. The addition of noise to a spot-wobbled picture was found to be more detrimental to the quality of the noninterlaced pictures than to the line-interlaced picture.