View source for 480i

{{Short description|Standard-definition video mode}}
{{About|the digital resolution|the analog NTSC color system|NTSC|the analog 525-line TV system|525 lines}}
{{More citations needed|date=April 2023}}
[[File:TV-line-count-world.svg|thumb|500px|SDTV resolution by nation: countries using 480i are in green.]]

'''480i''' is the [[video]] mode used for [[standard-definition television|standard-definition]] [[digital video]]<ref name=":0">{{cite web |title=What means 480i? - AfterDawn |url=https://www.afterdawn.com/glossary/term.cfm/480i |website=www.afterdawn.com}}</ref> in most of the [[Americas]] (with the exception of [[Argentina]], [[Paraguay]], and [[Uruguay]]), [[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 lines|525 line]] TV (defined in [[Rec. 601|BT.601]]) and is now used for digital TV broadcasts and home appliances such as game consoles and DVD disc players.<ref name=":0" /><ref>{{cite web |title=BT.601: Studio encoding parameters of digital television for standard 4:3 and wide screen 16:9 aspect ratios |url=https://www.itu.int/rec/R-REC-BT.601/ |publisher=ITU}}</ref>

The ''480'' identifies a vertical resolution of 480 lines, and the ''i'' identifies it as an [[Interlaced video|interlaced]] resolution. The [[Refresh rate|field rate]], which is 60&nbsp;[[Hertz|Hz]] (or 59.94&nbsp;Hz when used with NTSC color), is sometimes included when identifying the video mode, i.e. '''480i60'''; another notation, endorsed by both the [[International Telecommunication Union]] in [[Rec. 601|BT.601]]<ref>{{cite web |date=March 2011 |title=Recommendation ITU-R BT.601-7, Studio encoding parameters of digital television for standard 4:3 and wide-screen 16:9 aspect ratios |url=https://www.itu.int/dms_pubrec/itu-r/rec/bt/R-REC-BT.601-7-201103-I!!PDF-E.pdf |website=International Telecommunication Union}}</ref> 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 System M|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 ==
[[File:Balayage entrelace affichage trames.svg|alt=Interlaced scanning: display of the odd and even frames, and line returns|thumb|300px|Interlaced scanning: display of odd (green) and even (red) scanlines, and line return blanking periods (dotted)]]
For analog NTSC, there are a total of 525 [[Scan line|scanning lines]] per frame of which originally 483 lines were visible (241.5 visible lines per field + 21 lines of [[Vertical blanking interval|vertical blanking]] per field = 483 + 42 = 525 lines per frame) and later 480 (240 complete lines per field). [For quad video recording systems, the math suggests 15 transverse head passes, each consisting of 16 lines of video, are required to complete one field.]

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 (or 2 and a half lines) earlier than on all other systems, including [[CCIR System A|Systems A (405-line)]] and [[CCIR System E|E (819-line)]] 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 (first) field and the beginning of the odd (second field). 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 (first) 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 (and vice versa for the even field). The NTSC convention solved this confusion.<ref>Report 308-2 of the XIIth Plenary of the CCIR - Characteristics of TV systems.</ref>

For [[DV (video format)|DV-NTSC]] only 480 lines are used. The [[digital television|digitally transmitted]] horizontal resolution is usually 720 samples (which includes 16 samples for the horizontal sync and horizontal blanking) or 704 visible [[pixel]]s with an [[aspect ratio (image)|aspect ratio]] of 4:3 (with vertically rectangular pixels) and therefore a display resolution of 640&nbsp;×&nbsp;480 ([[Video Graphics Array|VGA]]); that is [[standard-definition television]] (SDTV) with a 4:3 aspect ratio (with square pixels).<ref>{{cite web |title=rpsoft 2000 software |url=http://www.rpsoft2000.com/information/hdtv.htm |access-date=1 June 2015 |work=rpsoft2000.com}}</ref><ref>{{cite web |title=480i |url=http://www.afterdawn.com/glossary/terms/480i.cfm |access-date=1 June 2015 |work=afterdawn.com}}</ref><ref>{{cite web |title=Glossary - 480i |url=http://reviews.cnet.com/4520-6029_7-6300992-1.html?tag=txt}}</ref>

The [[Refresh rate|field rate]] (not the [[frame rate]]) is usually (60/1.001) = 59.94&nbsp;[[hertz]] for color [[Television|TV]] and is often incorrectly rounded up to 60&nbsp;Hz. There are several conventions for written shorthands for the combination of resolution and rate: '''480i60''', '''480i/30''' ([[European Broadcasting Union|EBU]]/SMPTE always use frame rate to specify interlaced formats) and '''480/60i'''. 480i is usually used in countries that conventionally use NTSC (most of the Americas and [[Japan]]), because the 525 transmitted lines at 60&nbsp;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 (29.97) or 24 (23.976).

Color information is stored using the [[YCbCr]] [[color space]] (different from NTSC that used [[YIQ]]) with [[Chroma subsampling#4:2:2|4:2:2]] sampling (also different from NTSC) and following [[Rec. 601]] colorimetry.

480i can be transported by all major [[digital television]] formats ([[ATSC standards|ATSC]], [[DVB]] and [[ISDB]]) and on [[DVD]].

== See also ==
{{Portal|Television}}
* [[Enhanced-definition television]] (EDTV)
* [[List of common display resolutions]]
* [[8K resolution|4320p]], [[4K resolution#2160p resolution|2160p]], [[1080p]], [[1080i]], [[720p]], [[576p]], [[576i]], [[480p]], [[Low-definition television|360p]], [[Low-definition television|240p]]

== References ==
{{reflist}}

{{TV resolution}}
{{Video formats}}

[[Category:Television terminology]]
[[Category:Video formats]]