The improved display of 625-line television pictures

Conventional television, shown on the 625/50 standard with 2:1 interlacing of adjacent fields suffers several minor defects which become much more visible on large, bright displays. Large-area flicker and interline (interlace) twitter are easily seen, and line crawl, resulting from interlace, occassionally causes the picture to appear to be composed of only 312 1/2 lines. All these effects can be eliminated or reduced by displaying the received signal on a higher standard, such as 625/100 with 2:1 interlace or with sequential picture lines (1:1). The defects of 625/50, 2:1 displays and some of the ways in which they can be rendered less visible are described. Experimental monochrome results show that conversions to 625/100 with 2:1 interlace, 1250/100, 2:1 and 625/100, 1:1 all offer considerable prospects for improvement although the requirements of motion portrayal and vertical definition present conflicting requirements for the interpolation process. Less success was had with experiments using a 1250/100, 4:1 interlaced scanning structure, since it was found to be excessively prone to line crawl.