What is interlaced or progressive video?
There are basically two ways to display video: interlaced scan or progressive scan. Progressive scan, used in computer monitors and digital televisions, displays all the horizontal lines of a picture at one time as a single frame. Interlaced scan, used in standard television formats (NTSC, PAL, and SECAM), displays only half of the horizontal lines at a time. Interlacing relies on phosphor persistence of the TV tube to blend the fields together over a fraction of a second into a seemingly single picture. The advantage of interlaced video is that a high refresh rate (50 or 60 Hz) can be achieved with only half the bandwidth. The disadvantage is that the vertical resolution is essentially cut in half, and the video is often filtered to avoid flicker and other artifacts. DVDs are specifically designed to be displayed on interlaced-scan displays, which represent 99.9 percent of the more than one billion TVs worldwide. However, most DVD content comes from film, which is inherently progressi
