480i
480i is the video mode used for standard-definition digital video in most of the Americas, Japan, South Korea, Taiwan, the Philippines, and Myanmar. The other common standard definition digital standard, used in the rest of the world, is 576i.
It originated from the need for a standard to digitize analog 525 line TV and is now used for digital TV broadcasts and home appliances such as game consoles and DVD disc players.
The 480 identifies a vertical resolution of 480 lines, and the i identifies it as an interlaced resolution. The field rate, which is 60 Hz, is sometimes included when identifying the video mode, i.e. 480i60; another notation, endorsed by both the International Telecommunication Union in BT.601 and SMPTE in SMPTE 259M, includes the frame rate, as in 480i/30.
Although related, it should not be confused with the analog "525 lines" resolution, mandated by CCIR Systems M and J and usually paired with NTSC color. This association explains why 480i is sometimes inaccurately called "NTSC", even though NTSC only exists in the analog domain.
Technical details
For analog NTSC, there are a total of 525 scanning lines per frame of which originally 483 lines were visible and later 480.A full frame consists of two fields. One field contains the odd-numbered lines and the other contains the even ones. By convention an NTSC video frame is considered to start with an even field followed by an odd field. The disparity of the line numbering compared to other systems is solved by defining the line numbering to start five equalizing pulses earlier than on all other systems, including Systems A and E even though they had no equalizing pulses, on the first equalizing pulse following an active line or half line. This has the effect of placing a half line of video at the end of the even field and the beginning of the odd. Thus the line numbers correspond to the real lines of the video frame. On all other systems, the field was considered to start with the falling edge of the first field pulse which gave the confusing position that the odd field had a half a line of video occupying the latter half of a whole line and ended with a whole line of video but half a scanning line. The NTSC convention solved this confusion.
For DV-NTSC only 480 lines are used. The digitally transmitted horizontal resolution is usually 720 samples or 704 visible pixels with an aspect ratio of 4:3 and therefore a display resolution of 640 × 480 ; that is standard-definition television with a 4:3 aspect ratio.
The field rate is usually = 59.94 hertz for color TV and is often incorrectly rounded up to 60 Hz. There are several conventions for written shorthands for the combination of resolution and rate: 480i60, 480i/30 and 480/60i. 480i is usually used in countries that conventionally use NTSC, because the 525 transmitted lines at 60 hertz of analogue NTSC contain 480 visible ones.
In each case of the use of the ‘60’ terminology, it is merely shorthand for 59.94, to differentiate it from 30 or 24.
Color information is stored using the YCbCr color space with 4:2:2 sampling and following Rec. 601 colorimetry.
480i can be transported by all major digital television formats and on DVD.