Enhanced-definition television


Enhanced-definition television

Enhanced-definition television, extended-definition television, or EDTV is a CEA marketing shorthand term for certain digital television (DTV) formats and devices, used by the Consumer Electronics Association (CEA) of the United States. 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" and "576p" respectively) as opposed to interlaced scanning, commonly referred to as "480i" or "576i". High motion is optional for EDTV.

In other countries the outlook may be different. For example, in Australia the 576p digital TV system is officially recognized as high definition. [cite web|url=http://www.broadcastandmedia.com/articles/ff/0c0276ff.asp|title=SBS jubilant with its 576p HD broadcasts]

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. 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. The horizontal resolution is 704 or 720 pixels regardless of intended aspect ratio. Because the same number of horizontal pixels 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 854*480. However since no broadcasts use this pixel count, such displays always scale anything they display. (The only sources of 854*480 video are internet downloads, such as from iTunes, and some video games.) When 854*480 plasma displays were common, viewers found that while the sets were not theoretically HD, downscaled HD signals looked far better than DVDs on such sets. 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 - but only if playing a well mastered, progressively encoded disk at high data ratesFact|date=October 2008. (No more than 2 hours on a single layer diskFact|date=October 2008.) DVDs cannot encode high motion without resorting to interlaceFact|date=October 2008, so some important forms of EDTV cannot be delivered in this way. The Blu-ray format can encode all EDTV forms - but because HDTV is a primary selling point of Blu Ray disks, 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. The Playstation 2 was also EDTV compatible with a component connection. The Wii and Xbox 360 can output 480p via YPbPr component cables. The PlayStation 3 can also output in 480p and 576p via its HDMI, and 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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