1080i (the i meaning interlaced, differing from 1080p in which the p stands for progressive scan) is the shorthand name for a high-definition television (HDTV) video mode. The term assumes a widescreen aspect ratio of 16:9, implying a frame size of 1920×1080 pixels.
The field rate of 1080i is typically 60 Hz for countries that use or used System M as analog broadcast television system (such as United States, Canada and Japan) or 50 Hz for regions that traditionally used television systems with 25 frames/s rate (such as in Europe, Australia, much of Asia, Africa). Both variants can be carried by both major digital television transmission formats: ATSC and DVB.
The frame rate can be implied by the context, while the field rate is generally specified after the letter i, such as “1080i60”. In this case 1080i60 refers to 60 fields per second or 30 frames per second. The European Broadcasting Union (EBU), prefers to use the resolution andframe rate (not field rate) separated by a slash, as in 1080i/30 and 1080i/25, likewise 480i/30 and 576i/25. Resolutions of 1080i60 or 1080i50 often refers to 1080i/30 or 1080i/25 in EBU notation.
1080i is directly compatible with CRT-based HDTV sets and is displayed natively in interlaced form, but must be deinterlaced and often scaled for display on modern progressive-scan LCD and plasma TV sets. Depending on the television’s video processor the resulting video quality may vary.
BBC HD broadcasts in this format. In the United States, 1080i is the preferred format for CBS, NBC and The CW, though some affiliates (especially those that broadcast two digital subchannels in HD) do broadcast in 720p. Fox and ABC/ESPN broadcast in 720p.