To understand Progressive Scanning for DVD material, you must first understand how the image is laid on the DVD disk. DVD standard states that the video image is encoded in 720 lines horizontally and 480 lines vertically. This image is defined as a "frame", a full snap of a picture from the original film with the full 720x480 lines of image.
This image will be divided to two halves by taking each alternate lines to create a "field". The division of the picture is required to display on an analog NTSC set which can show only half the picture in each pass of the electron gun, hence the term "interlaced". In the next pass, it will draw the alternate line and repeat the scan 60 times per second. The process reveals dark lines inbetween each line of the picture called scan lines. The eye can be fooled on smaller TV sets, but the same image blown up to twice, three times, or four times it's original size becomes torturous as is the case with large screen displays.
Progressive scan imaging was designed to show both of the fields in one pass, doubling the scan frequency and eliminating the artifact of interlacing. To do so required re-engineering the display device and the type of input connector used. To define the interlaced process, a video signal is described as 480i, whereas progressive signals are identified as 480p.
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