Enhanced-definition television

From Wikipedia, the free encyclopedia
  (Redirected from Enhanced definition)
Jump to: navigation, search
"EDTV" redirects here. For the 1999 movie directed by Ron Howard, see EDtv. For the former television channel, see Emirates Dubai Television.

Enhanced-definition television, or extended-definition television (EDTV) is an American Consumer Electronics Association (CEA) marketing shorthand term for certain digital television (DTV) formats and devices. Specifically, this term defines formats that deliver a picture 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-line or 576-line signals in progressive scan, commonly referred to as 480p (NTSC-HQ) 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 definitions may vary.

Connectivity[edit]

As EDTV signals require more bandwidth (due to frame doubling) than is feasible with SDTV connection standards, such as composite video, SCART or S-Video, then 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 consoles 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[edit]

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. Since the same number of horizontal pixels are used in 4:3 and 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 show. The only sources of 852 × 480 video are Internet downloads, such as from iTunes, and some video games. Unlike 1080i and SDTV formats, progressive displays (such as plasma displays and LCDs) can show EDTV signals without the need to interlace them first. This can result in a reduction of motion artifacts. However to achieve this most progressive displays require the broadcast to be frame doubled (i.e., 25 to 50 and 30 to 60) to avoid the same motion flicker issues that interlacing fixes.

DVDs[edit]

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 2:2 or 3:2 pulldown conversion internally, before feeding the output to (usually) an interlaced display, or here, a progressive 576p or 480p.[2]

The progressive 24 fps DVD will have a unifying effect on PAL and NTSC, just as film does, perhaps requiring conversion of the number of lines but without a conflict between field and frame rate. The player converts the video to the more-conventional video formats, on the fly, by simply repeating each field. It converts for PAL (referring here to 625 line 575 active line used with PAL as well as the chrominance aspects), by repeating each frame twice with a corresponding interlace, or for NTSC, by repeating some 480p frames 2 times and others 3 times (3:2 pulldown), to make 24 fps material play at 30fps, or 60 fields per second.[3][4]

On an EDTV display, or on HDTVs in 480p mode, DVD players can display progressive disc content without needing to convert it to interlaced format. Various signal processing tricks are then used to fake the progressive scan; the quality of this depends on the quality of the upconversion process.

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

Gaming[edit]

The video resolution of video game consoles reached EDTV specifications starting with the Sega Dreamcast, becoming the first mainstream console with a VGA output, supporting EDTV. The PlayStation 2, Nintendo GameCube, Microsoft 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 outputs EDTV via its HDMI and component video (YPBPR) connections; 480p is only available on NTSC consoles while 576p is only available on PAL consoles.

References[edit]

  1. ^ CNET Networks - Enhanced Definition Television
  2. ^ "Progressive Scan - What You Need To Know About Progressive Scan and How It Affects What You See on a Television Screen". Hometheater.about.com. 2011-04-06. Retrieved 2011-04-22. 
  3. ^ explanation of progressive scan http://www.webopedia.com/TERM/P/progressive_scan.html
  4. ^ HiFi writer progressive scan dvd players critique and concern over lack of lines for 625 PAL resolution www.hifi-writer.com/he/progscan/progscan.htm