This chart shows the most common display resolutions, 720p being one of the 16:9 formats shown in blue.
720p (720 lines progressive) is a progressive HD signal format with 720 horizontal lines/1280 columns and an aspect ratio (AR) of 16:9, normally known as widescreen HD (1.78:1). All major HD broadcasting standards (such as SMPTE 292M) include a 720p format, which has a resolution of 1280×720p.
720i (720 lines interlaced) is an erroneous term found in numerous sources and publications. Typically, it is a typographical error in which the author is referring to the 720p HDTV format. However, in some cases it is incorrectly presented as an actual alternative format to 720p.[3] No proposed or existing broadcast standard permits 720 interlaced lines in a video frame at any frame rate.[4]
Progressive scanning reduces the need to prevent flicker by anti-aliasing single high contrast horizontal lines.[5][6] It is also easier to perform high-quality 50<->60 Hz conversion and slow-motion clips with progressive video.
^It is, however, more commonly broadcast at (60/1.001), or precisely 59.940059, matching the NTSC SDTV field rate; this and the 50.00 Hz of PAL are still the second and third highest standard framerates.[2]
