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Enhanced-definition television, extended-definition television, or EDTV is a United States Consumer Electronics Association (CEA) marketing shorthand term for certain digital television (DTV) formats and devices. Specifically, this term defines formats that deliver a picture that is superior to that of standard-definition television (SDTV), but not as detailed as high-definition television (HDTV).

The term refers to devices capable of displaying 480 or 576-line signals in progressive scan (commonly referred to as "480p (NTSC)" and "576p (PAL)" respectively) as opposed to interlaced scanning, commonly referred to as "480i (NTSC)" or "576i (PAL)". High-motion is optional for EDTV.[1]

In other countries the outlook may be different. For example, in Australia the 576p digital TV system is officially recognised as high definition, although HD broadcasts in Australia have to be a minimum of 720p.[2]

TV units that have a hardware resolution approximately in the middle of HDTV and SDTV are marketed as "HD Ready", such units may be able to display 720p without downsampling, but are often based around 1280x800 to 1440x900 panels and so cannot display 1080i or 1080p. "Full HD" televisions must use, at least, 1920x1080 panels.

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Connectivity

As EDTV signals require more bandwidth than is feasible with SDTV connection standards, such as composite video or S-Video, higher bandwidth media must be used to accommodate the additional data transfer. To achieve EDTV, consumer electronic devices such as a progressive scan DVD player or modern video game console must be connected through at least a component video cable (typically using 3 RCA cables for video), a VGA connector, or a DVI or HDMI connector. For over-the-air television broadcasts, EDTV content uses the same connectors as HDTV.

Broadcast and displays

EDTV broadcasts use less digital bandwidth than HDTV, so TV stations can broadcast several EDTV stations at once. Like SDTV, EDTV signals are broadcast with non-square pixels. Because the same amount of horizontal pixels are used in 4:3 or 16:9 broadcasts, the 16:9 mode is sometimes referred to as anamorphic widescreen. Most EDTV displays use square pixels, yielding a resolution of 852×480. However since no broadcasts use this pixel count, such displays always scale anything they display. (The only sources of 852×480 video are internet downloads, such as from iTunes, and some video games). When Plasma EDTVs were common, viewers found that while the TVs were not theoretically HD, downscaled HD signals looked far better than DVDs on such TVs. Unlike 1080i and SDTV formats, plasma displays can show EDTV signals without the need to de-interlace them first. This can result in a reduction of motion artifacts.

DVDs

The progressive output of a DVD player can be considered the baseline for EDTV. Movies shot at 24 frames per second (fps) are often encoded onto a DVD at 24 fps progressive, and most DVD players do the 3:2 pulldown conversion internally before feeding the output to (usually) an interlaced display, or here, a progressive 480p display (by repeating some 480p frames 2 times and others 3 times (3:2 pulldown), to make 24fps material play at 30fps, or 60 fields per second). On an EDTV display, or on HDTVs in 480p mode, DVD players can display progressive disc content without needing to convert it to interlaced. Various signal processing tricks are then used to fake progressive scan, and the quality of this depends on how good the upconversion process is.

Blu-ray Disc and HD DVD formats can encode all EDTV forms - but because HDTV is a primary selling point of Blu-ray/HD DVD discs, to date, this has been used only on certain bonus content.

Gaming

The video resolution of video game consoles reached EDTV specifications starting with the Sega Saturn, with NiGHTS into Dreams..., Christmas NiGHTS, Panzer Dragoon II Zwei, and High Velocity being the only supported games. The Dreamcast expanded on this, becoming the first mainstream console with a VGA output, supporting EDTV. The PlayStation 2, Nintendo GameCube, Xbox and Wii are also EDTV compatible with a component connection. The Xbox 360 can output 480p via YPbPr component, VGA and HDMI (newer models only) cables. The PlayStation 3 also outputs in 480p (NTSC) and 576p (PAL) via its HDMI, component video(Y/Pr/Pb), and RGB connections. Also, some consumer devices, such as a video game console, typically use a horizontal resolution of 640 square pixels when outputting an EDTV signal, which is already a 4:3 format.

References

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