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1080i is the shorthand name for a category of video modes. The number 1080 stands for 1080 lines of vertical resolution, while the letter i stands for interlaced or non-progressive scan. 1080i is considered to be an HDTV video mode. The term usually assumes a widescreen aspect ratio of 16:9, implying a horizontal resolution of 1920 pixels and a frame resolution of 1920 × 1080 or about 2.07 million pixels, and a field resolution of 1920 × 1080 / 2 (because it's interlaced) or about 1.04 million pixels. The field rate (not the frame rate) in hertz can be either implied by the context or specified after the letter i. The two field rates in common use are 50 and 60 Hz, with the former (1080i50) generally being used in traditional PAL and SECAM countries (Europe, Australia, much of Asia, Africa), the latter (1080i60) in traditional NTSC countries (e.g. United States, Canada and Japan). Both variants can be transported by both major digital television formats, ATSC and DVB.

Some people prefer to use the line number of fields, which is half that of frames, in their nomenclature and thus call this mode 540i, likewise 240i and 288i. Others, including the European Broadcasting Union (EBU), prefer to use the frame rate instead of the field rate and separate it with a solidus from the resolution as in 1080i/30 and 1080i/25, likewise 480i/30 and 576i/25.

1080i is directly compatible with CRT-based HDTV sets. CRT-based HDTV never entered the market in large volumes and is today regarded as outdated technology. 1080i is compatible with newer 720p- and 1080p-based televisions but must be deinterlaced first in order to be displayed on those sets.

Due to a revision of the NTSC format when color became available, the field rate of actual 1080i broadcasts is usually 0.1% slower than is implied. For example, a 1080i60 or "60 Hz" transmission actually displays about 59.94 fields each second. Both the straight 24/30/60 and 23.976/29.97/59.94 frequencies are supported by current standards.

Progressive format 1080p50 or 60 is foreseen as the future broadcasting standard for production<ref>EBU Recommendation FUTURE HIGH DEFINITION TELEVISION SYSTEMS</ref>.

For a comparison between 1080i and 720p, see the 720p article.

[edit] See also

• 1080p, 720p, 576p, 480p
• High-definition television (HDTV)

[edit] References

<references/>

[edit] External links

• High Definition (HD) Image Formats for Television Production (EBU technical publication)
• 1080i vs. 1080p HDTV: should you care?
• HDTV Org Independent guide to High Definition TV

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