Enhanced-definition television

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Enhanced-definition television, or extended-definition television (EDTV) is a 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).

Contents

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/SECAM) respectively, as opposed to interlaced scanning, commonly referred to as 480i (NTSC) or 576i (PAL, SECAM). High-motion is optional for EDTV. [1]

In other countries definitions may vary.

Connectivity

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), 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

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 some video games. Unlike 1080i and SDTV formats, progressive displays (such as plasma displays and LCDs) can show EDTV signals without the need to de-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

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, this is only used for certain bonus content such as featurettes, deleted scenes, interviews and behind the scenes documentaries on the making of the film.

Gaming

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.

Despite 576p being a valid output from the PS2's component out, it is never used by any games released in PAL territories; instead the few games retaining progressive scan mode in their PAL localisations output in 480p. There are homebrew solutions available to force the output to progressive scan mode (which also in turn allows 60Hz modes for 720p and 1080p: neither of which were otherwise used in any capacity officially).

Related Research Articles

Standard-definition television Original analog television systems

Standard-definition television is a television system which uses a resolution that is not considered to be either high or enhanced definition. SDTV and high-definition television (HDTV) are the two categories of display formats for digital television (DTV) transmissions. "Standard" refers to the fact that it was the prevailing specification for broadcast television in the mid- to late-20th century.

Video Electronic moving image

Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video was first developed for mechanical television systems, which were quickly replaced by cathode ray tube (CRT) systems which were later replaced by flat panel displays of several types.

Interlaced video Technique for doubling the perceived frame rate of a video display

Interlaced video is a technique for doubling the perceived frame rate of a video display without consuming extra bandwidth. The interlaced signal contains two fields of a video frame captured consecutively. This enhances motion perception to the viewer, and reduces flicker by taking advantage of the phi phenomenon.

Progressive scanning is a format of displaying, storing, or transmitting moving images in which all the lines of each frame are drawn in sequence. This is in contrast to interlaced video used in traditional analog television systems where only the odd lines, then the even lines of each frame are drawn alternately, so that only half the number of actual image frames are used to produce video. The system was originally known as "sequential scanning" when it was used in the Baird 240 line television transmissions from Alexandra Palace, United Kingdom in 1936. It was also used in Baird's experimental transmissions using 30 lines in the 1920s. Progressive scanning became universally used in computer screens beginning in the early 21st century.

Telecine Process for broadcasting content stored on film stock

Telecine is the process of transferring motion picture film into video and is performed in a color suite. The term is also used to refer to the equipment used in the post-production process. Telecine enables a motion picture, captured originally on film stock, to be viewed with standard video equipment, such as television sets, video cassette recorders (VCR), DVD, Blu-ray Disc or computers. Initially, this allowed television broadcasters to produce programmes using film, usually 16mm stock, but transmit them in the same format, and quality, as other forms of television production. Furthermore, telecine allows film producers, television producers and film distributors working in the film industry to release their products on video and allows producers to use video production equipment to complete their filmmaking projects. Within the film industry, it is also referred to as a TK, because TC is already used to designate timecode. Motion picture film scanners are similar to telecines.

Advanced Television Systems Committee (ATSC) standards are an American set of standards for digital television transmission over terrestrial, cable and satellite networks. It is largely a replacement for the analog NTSC standard and, like that standard, is used mostly in the United States, Mexico, Canada, and South Korea. Several former NTSC users, in particular Japan, have not used ATSC during their digital television transition, because they adopted their own system called ISDB.

Display resolution Number of distinct pixels in each dimension that can be displayed

The display resolution or display modes of a digital television, computer monitor or display device is the number of distinct pixels in each dimension that can be displayed. It can be an ambiguous term especially as the displayed resolution is controlled by different factors in cathode ray tube (CRT) displays, flat-panel displays and projection displays using fixed picture-element (pixel) arrays.

480p is the shorthand name for a family of video display resolutions. The p stands for pixels scan, i.e. non-interlaced. The 480 denotes a vertical resolution of 480 pixels, usually with a horizontal resolution of 640 pixels and 4:3 aspect ratio or a horizontal resolution of 854 or less pixels for an approximate 16:9 aspect ratio. Since a pixel count must be a whole number, in Wide VGA displays it is generally rounded up to 854 to ensure inclusion of the entire image. The frames are displayed progressively as opposed to interlaced. 480p was used for many early plasma televisions. Standard definition has always been a 4:3 aspect ratio with a pixel resolution of 640 × 480 at 60Hz for NTSC regions, and 720 or 768 × 576 for PAL regions (1024 wide for widescreen displays. However, standard definition defines a 15.7Khz horizontal scanrate, which means that interlacing has to be used for those resolution modes. The lowercase letter "p" in 480p stands for progressive, so the two must not be confused.

720p Video resolution

720p is a progressive HDTV signal format with 720 horizontal lines and an aspect ratio (AR) of 16:9, normally known as widescreen HDTV (1.78:1). All major HDTV broadcasting standards include a 720p format, which has a resolution of 1280×720; however, there are other formats, including HDV Playback and AVCHD for camcorders, that use 720p images with the standard HDTV resolution. The frame rate is standards-dependent, and for conventional broadcasting appears in 50 progressive frames per second in former PAL/SECAM countries, and 59.94 frames per second in former NTSC countries.

1080i is a combination of frame resolution and scan type. 1080i is used in high-definition television (HDTV) and high-definition video. The number "1080" refers to the number of horizontal lines on the screen. The "i" is an abbreviation for "interlaced"; this indicates that only the odd lines, then the even lines of each frame are drawn alternately, so that only half the number of actual image frames are used to produce video. A related display resolution is 1080p, which also has 1080 lines of resolution; the "p" refers to progressive scan, which indicates that the lines of resolution for each frame are "drawn" on the screen in sequence.

480i Standard-definition video mode

480i is the video mode used for standard-definition analog or digital television in the Caribbean, Myanmar, Japan, South Korea, Taiwan, Philippines, Laos, Western Sahara, and most of the Americas. The 480 identifies a vertical resolution of 480 lines, and the i identifies it as an interlaced resolution. The field rate, which is 60 Hz, is sometimes included when identifying the video mode, i.e. 480i60; another notation, endorsed by both the International Telecommunication Union in BT.601 and SMPTE in SMPTE 259M, includes the frame rate, as in 480i/30. The other common standard, used in the other parts of the world, is 576i.

576i Standard-definition video mode

576i is a standard-definition video mode originally used for terrestrial television in most countries of the world where the utility frequency for electric power distribution is 50 Hz. Because of its close association with the colour encoding system, it is often referred to as simply PAL, PAL/SECAM or SECAM when compared to its 60 Hz NTSC-colour-encoded counterpart, 480i. In digital applications it is usually referred to as "576i"; in analogue contexts it is often called "625 lines", and the aspect ratio is usually 4:3 in analogue transmission and 16:9 in digital transmission.

576p is the shorthand name for a video display resolution. The p stands for progressive scan, i.e. non-interlaced, the 576 for a vertical resolution of 576 pixels, usually with a horizontal resolution of 768 or 1024, depending of the relationship aspect. The 576p quality was decided as the default quality when converting from VHS to digital. 576p is considered standard definition for PAL video. The frame rate can be given explicitly after the letter.

High-definition video is video of higher resolution and quality than standard-definition. While there is no standardized meaning for high-definition, generally any video image with considerably more than 480 vertical scan lines or 576 vertical lines (Europe) is considered high-definition. 480 scan lines is generally the minimum even though the majority of systems greatly exceed that. Images of standard resolution captured at rates faster than normal, by a high-speed camera may be considered high-definition in some contexts. Some television series shot on high-definition video are made to look as if they have been shot on film, a technique which is often known as filmizing.

1080p Video mode

1080p is a set of HDTV high-definition video modes characterized by 1,920 pixels displayed across the screen horizontally and 1,080 pixels down the screen vertically; the p stands for progressive scan, i.e. non-interlaced. The term usually assumes a widescreen aspect ratio of 16:9, implying a resolution of 2.1 megapixels. It is often marketed as Full HD or FHD, to contrast 1080p with 720p resolution screens. Although 1080p is sometimes informally referred to as 2K, these terms reflect two distinct technical standards, with differences including resolution and aspect ratio.

Low-definition television (LDTV) refers to TV systems that have a lower screen resolution than standard-definition TV systems. The term is usually used in reference to digital TV, in particular when broadcasting at the same resolution as low-definition analog TV systems. Mobile DTV systems usually transmit in low definition, as do all slow-scan TV systems.

Pixel aspect ratio

Pixel aspect ratio is a mathematical ratio that describes how the width of a pixel in a digital image compares to the height of that pixel.

Dreamcast VGA

The Dreamcast VGA Box is an accessory for Sega's Dreamcast video game console that allows it to connect to a video display such as a computer monitor or a HDTV set through a VGA port. Because the Dreamcast hardware can produce a VGA-compatible video signal natively, this connection provides improved picture quality compared to standard composite video or S-Video connections, along with support for progressive scan video.

A progressive scan DVD player is a DVD player that can produce video in a progressive scan format such as 480p (NTSC) or 576p (PAL). Players which can output resolutions higher than 480p or 576p are often called upconverting DVD players.

High-definition television (HD) describes a television system providing an image resolution of substantially higher resolution than the previous generation of technologies. The term has been used since 1936, but in modern times refers to the generation following standard-definition television (SDTV), often abbreviated to HDTV or HD-TV. It is the current de facto standard video format used in most broadcasts: terrestrial broadcast television, cable television, satellite television and Blu-ray Discs.

References

  1. CNET Networks - Enhanced Definition Television Archived 2009-06-11 at the Wayback Machine
  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