480i is a shorthand name of a video mode, to be specific, either US NTSC television system or digital television systems with the same characteristics. The number 480 means there are 480 lines that contain picture information, while the NTSC actually has a total of 525 lines, only 483 of them are used to display the image for DV-NTSC.
The digitally transmitted horizontal resolution is often 720 samples (including 16 samples for both horizontal sync and horizontal blanking) or 704 visible pixels that has an aspect ratio of 4:3 (with vertically rectangular pixels) which means a display resolution of 640 × 480 (VGA); that is standard-definition television (shortened as SDTV) with a 4:3 aspect ratio (with square pixels).
- "Some Explanation of HDTV Terms for U.S. type Television Systems". rpsoft 2000. Retrieved 2014-07-26.