The Meaning of 720p, 1080p and 1080i
720p is a standard of high-grade HDTV signal format developed by the Society of Motion Picture and Television Engineers(SMPTE) with the effective display format of 1208×720. while 1080p is the highest grade of that, effective display format: 1920×1080. Then what’ the differences between 1080p and 1080i? “p”here following the number is the abbr of Progressive which means progressive scan, while “i” stands for interlaced scan. 1080i indicates that each frame of video is diaplayed in alternative fields with 30 times per second, while 1080p refreshing the screen 60 times per second. Therefore, the image of 1080p is more smooth and stable than that of 1080i. But both of them represent a 1920×1080 ixel resolution.
(Interlaced scan: the technology was firstly launched on the display of 8514A by IBM. Its principle is firstly scan the odd row then the even row when conducting display scaning, the complete image is constituded by the twice scan. This techonology is easy to achieve with lower cost, but when the resolution is high than 800×600, the image would flash and unstable. So it is less used on present display with big screen.
Progressive scan: opposite to interlaced, it scans line after line in sepuence. No flashing and more steady. So it it widely used nowadays.)
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