Thursday, January 29, 2015

About Progressive Scan

Progressive scanning refers to a way of displaying, storing or transmitting moving images in which all the lines of each frame are drawn in sequence. It is also known as noninterlaced scanning alternatively. In comparison with interlaced video, progressive scanning is a way distinguished from interlaced scanning. Interlaced video is usually adopted in traditional analog television systems in which only the odd lines, then the even lines of each frame (each image called a video field) are drawn one after another. As a result, only half of the number of actual image frames are utilized to produce video.

As a matter of fact, progressive scanning is known as “sequential scanning” in the first place when it was adopted in the Baird 240 line television transmissions from Alexandra Palace, United Kingdom in 1936. Nowadays, progressive scanning has been universally adopted in computing.

Progressive scanning is applied in the scanning and storing of film-based material on DVDs. It was agreed that all film transmissions by HDTV would be broadcast with progressive scan in the US. Even though the video signal is sent interlaced, an HDTV will convert it to progressive scan.

Progressive scanning has been applied on most Cathode ray tube (CRT) computer monitors, all LCD computer monitors, and most HDTVs for the display resolutions are progressive by nature. Other CRT-type displays, such as SDTVs, will only display interlaced video.

Generally speaking, some TVs and most video projectors have one or more progressive scan inputs. Before HDTV became well received, some high end displays supported 480p. Under such conditions, these displays were able to be used with devices outputting progressive scan. For instance, some progressive scan DVD players and certain video game consoles are included. HDTVs support the 480p and 720p resolutions which have been progressively scanned. Compared with lower resolution HDTV models, the 1080p displays are usually more expensive.