720p

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720p is the shorthand name for a category of video modes. The number 720 stands for 720 lines of vertical resolution, while the letter p stands for progressive scan or non-interlaced. 720p is considered to be an HDTV video mode. The term usually assumes a widescreen aspect ratio of 16:9, implying a horizontal resolution of 1280 lines and a frame resolution of 1280 x 720 or about 0.92 million pixels. The frame rate (in this case equal to the field rate) can be either implied by the context or specified in hertz after the letter p. The five 720p frame rates in common use are 24, 25, 30, 50 and 60 Hz. In general, traditional PAL and SECAM countries (Europe, Australia, much of Asia, Africa, and South America) are or will be using 720p25 and 720p50, whereas traditional NTSC countries (North America, Japan) are using 720p24 (for movies), 720p30, and 720p60. All variants can be transported by both major digital television formats, ATSC and DVB.

720p is directly compatible with newer flat panel technology such as plasma and LCD which are inherently progressive and must perform deinterlacing to display 1080i source material. 720p must be scan converted for display on most CRT-based consumer televisions which are generally interlaced-only display devices. However, most modern CRT-based computer monitors are progressive-only devices that can be run at 1280×720p60 either natively or through a refresh rate tweaking utility.

720p versus 1080i

Some U.S. broadcasters use 720p60 as their primary high-definition format; others use the 1080i standard. While 720p presents a complete 720 line frame to the viewer between 24 to 60 times each second (depending on the format), 1080i presents the picture as 50 or 60 partial 540 line "fields" (24 complete 1080-line fields, or "24p" is included in the ATSC standard though) which the human eye or a deinterlacer built into the display device must visually and temporally combine to build a 1080 line picture. The main tradeoff between the two is that 1080i may show more detail than 720p for a stationary shot of a subject at the expense of introducing interlace artifacts from a motion of the camera (such as a pan) or motion of the subject. 720p is used by ABC and ESPN because the smoother image is desirable for fast-action sports telecasts. Fox Broadcasting Company uses the tagline "the nation's finest high-definition standard" in advertising its 720p programming.

The European Broadcasting Union (EBU) recommends to its members to use 720p50 for emission with the possibility of 1080i50 on a programme-by-programme choice and 1080p50 as a future option. [EBU Technical Recommendation R112 - 2004]http://www.ebu.ch/en/technical/trev/trev_home.html The BBC is one of the only members so far transmitting in HDTV. All commercial European HDTV services so far use 1080i50.

Proponents of 720p further argue that at the average viewing distance, with the average size of consumer HDTV sets, the human eye would not actually be able to perceive the difference in resolution between 720p and 1080i. This is because the 720p image "saturates" the perceivable resolution of the eye at this distance—watching from much closer to the monitor, however, the viewer would be able to see the difference.

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