Low-definition television
Encyclopedia
Low-definition television or LDTV refers to television system
s that have a lower screen resolution than standard-definition television
systems. The term is usually used in reference to digital television
, in particular when broadcasting
at the same (or similar) resolution as low-definition analog TV systems. Mobile DTV systems usually transmit in low definition, as do all slow-scan TV systems.
, where mass distribution of higher-resolution video files could overwhelm computer servers and take too long to download. Most mobile phone
s and portable devices such as Apple’s video iPod
, or Sony’s PlayStation Portable
use LDTV video, as higher-resolution files would be excessive to the needs of their small screens (320 × 240 and 480 × 272 pixel
s respectively). The current generation of iPods have LDTV screens, as do the first three generations of iPhone
(480 × 320).
A VHS
videotape
could be considered SDTV due to its resolution (approximately 320 × 480i), but using VHS for professional production will yield results comparable to LDTV because of VHS's low bandwidth. VHS supports interlace and high motion
, which are not typical of LDTV signals. Professional-level Betacam SP tape produces approx 440 × 486; some college
TV studios use Super VHS at ~560 × 486.
Older video game console
and home computers generated a nonstandard NTSC or PAL signal which placed both fields on top of each other. This is equivalent to 240p and 288p respectively. Conversely, the FCC forbade TV stations from broadcasting in this format. The Video CD
format was introduced on such a console (CD-i
), and it likewise uses a progressive
LDTV signal (352 × 240 or 352 × 288), which is half the vertical resolution of SDTV.
With the introduction of 16-bit game consoles, 480i was supported for the first time, but rarely used due to limited memory and processing power. Thus, 240p remained the primary format on all fifth generation consoles
(Sega Saturn, PlayStation and Nintendo 64) With the advent of sixth generation consoles
and the launch of the Dreamcast, 480i use become more common, and 240p usage declined.
More recent game systems tend to use only properly interlaced NTSC or PAL in addition to higher resolution modes, except when running games designed for older, compatible systems in their native modes. The PlayStation 2
generates 240p/288p if a PlayStation game calls for this mode, as do many Virtual Console
emulated games on Wii
. Nintendo's official software development kit
documentation refers to 240p as 'non-interlaced mode' or 'double-strike'.
Shortly after the launch of the Wii Virtual Console service many users with component video
cables experienced problems displaying some Virtual Console games due to certain TV models/manufacturers not supporting 240p over a component video connection. Nintendo's solution was to implement 'Wii Component Cable Interlace Mode' which forces the emulator to output 480i instead of 240p, however many game released prior have still not been updated.
, DMB
, or ATSC-M/H
. However, this kind of LDTV transmission technology is based on existent LDTV teleconferencing standards that have been in place for a decade or more.
Television system
A television system is a Canadian term for a group of television stations which share common ownership, branding, and programming, but are not considered a full television network....
s that have a lower screen resolution than standard-definition television
Standard-definition television
Sorete-definition television is a television system that uses a resolution that is not considered to be either enhanced-definition television or high-definition television . The term is usually used in reference to digital television, in particular when broadcasting at the same resolution as...
systems. The term is usually used in reference to digital television
Digital television
Digital television is the transmission of audio and video by digital signals, in contrast to the analog signals used by analog TV...
, in particular when broadcasting
Broadcasting
Broadcasting is the distribution of audio and video content to a dispersed audience via any audio visual medium. Receiving parties may include the general public or a relatively large subset of thereof...
at the same (or similar) resolution as low-definition analog TV systems. Mobile DTV systems usually transmit in low definition, as do all slow-scan TV systems.
Sources
The most common source of LDTV programming is the InternetInternet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
, where mass distribution of higher-resolution video files could overwhelm computer servers and take too long to download. Most mobile phone
Mobile phone
A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...
s and portable devices such as Apple’s video iPod
IPod
iPod is a line of portable media players created and marketed by Apple Inc. The product line-up currently consists of the hard drive-based iPod Classic, the touchscreen iPod Touch, the compact iPod Nano, and the ultra-compact iPod Shuffle...
, or Sony’s PlayStation Portable
PlayStation Portable
The is a handheld game console manufactured and marketed by Sony Corporation Development of the console was announced during E3 2003, and it was unveiled on , 2004, at a Sony press conference before E3 2004...
use LDTV video, as higher-resolution files would be excessive to the needs of their small screens (320 × 240 and 480 × 272 pixel
Pixel
In digital imaging, a pixel, or pel, is a single point in a raster image, or the smallest addressable screen element in a display device; it is the smallest unit of picture that can be represented or controlled....
s respectively). The current generation of iPods have LDTV screens, as do the first three generations of iPhone
IPhone
The iPhone is a line of Internet and multimedia-enabled smartphones marketed by Apple Inc. The first iPhone was unveiled by Steve Jobs, then CEO of Apple, on January 9, 2007, and released on June 29, 2007...
(480 × 320).
A VHS
VHS
The Video Home System is a consumer-level analog recording videocassette standard developed by Victor Company of Japan ....
videotape
Videotape
A videotape is a recording of images and sounds on to magnetic tape as opposed to film stock or random access digital media. Videotapes are also used for storing scientific or medical data, such as the data produced by an electrocardiogram...
could be considered SDTV due to its resolution (approximately 320 × 480i), but using VHS for professional production will yield results comparable to LDTV because of VHS's low bandwidth. VHS supports interlace and high motion
High motion
High motion is the characteristic of video or film footage displayed possessing a sufficiently high frame rate that moving images do not blur or strobe even when tracked closely by the eye. The most common forms of high motion are NTSC and PAL video at their native display rates...
, which are not typical of LDTV signals. Professional-level Betacam SP tape produces approx 440 × 486; some college
College
A college is an educational institution or a constituent part of an educational institution. Usage varies in English-speaking nations...
TV studios use Super VHS at ~560 × 486.
Older video game console
Video game console
A video game console is an interactive entertainment computer or customized computer system that produces a video display signal which can be used with a display device to display a video game...
and home computers generated a nonstandard NTSC or PAL signal which placed both fields on top of each other. This is equivalent to 240p and 288p respectively. Conversely, the FCC forbade TV stations from broadcasting in this format. The Video CD
Video CD
Before the advent of DVD and Blu-ray, the Video CD became the first format for distributing films on standard 120 mm optical discs. The format is a standard digital format for storing video on a Compact Disc...
format was introduced on such a console (CD-i
CD-i
CD-i, or Compact Disc Interactive, is the name of an interactive multimedia CD player developed and marketed by Royal Philips Electronics N.V. CD-i also refers to the multimedia Compact Disc standard used by the CD-i console, also known as Green Book, which was developed by Philips and Sony...
), and it likewise uses a progressive
Progressive scan
Progressive scanning is a way of displaying, storing, or transmitting moving images in which all the lines of each frame are drawn in sequence...
LDTV signal (352 × 240 or 352 × 288), which is half the vertical resolution of SDTV.
With the introduction of 16-bit game consoles, 480i was supported for the first time, but rarely used due to limited memory and processing power. Thus, 240p remained the primary format on all fifth generation consoles
History of video game consoles (fifth generation)
The fifth-generation era refers to the computer and video games, video game consoles, and video game handhelds available at stores...
(Sega Saturn, PlayStation and Nintendo 64) With the advent of sixth generation consoles
History of video game consoles (sixth generation)
The sixth-generation era refers to the computer and video games, video game consoles, and video game handhelds available at the turn of the 21st century. Platforms of the sixth generation include the Sega Dreamcast, Sony PlayStation 2, Nintendo GameCube, and Microsoft Xbox...
and the launch of the Dreamcast, 480i use become more common, and 240p usage declined.
More recent game systems tend to use only properly interlaced NTSC or PAL in addition to higher resolution modes, except when running games designed for older, compatible systems in their native modes. The PlayStation 2
PlayStation 2
The PlayStation 2 is a sixth-generation video game console manufactured by Sony as part of the PlayStation series. Its development was announced in March 1999 and it was first released on March 4, 2000, in Japan...
generates 240p/288p if a PlayStation game calls for this mode, as do many Virtual Console
Virtual console
A virtual console – also known as a virtual terminal – is a conceptual combination of the keyboard and display for a computer user interface. It is a feature of some operating systems such as UnixWare, Linux, and BSD, in which the system console of the computer can be used to switch between...
emulated games on Wii
Wii
The Wii is a home video game console released by Nintendo on November 19, 2006. As a seventh-generation console, the Wii primarily competes with Microsoft's Xbox 360 and Sony's PlayStation 3. Nintendo states that its console targets a broader demographic than that of the two others...
. Nintendo's official software development kit
Software development kit
A software development kit is typically a set of software development tools that allows for the creation of applications for a certain software package, software framework, hardware platform, computer system, video game console, operating system, or similar platform.It may be something as simple...
documentation refers to 240p as 'non-interlaced mode' or 'double-strike'.
Shortly after the launch of the Wii Virtual Console service many users with component video
Component video
Component video is a video signal that has been split into two or more component channels. In popular use, it refers to a type of component analog video information that is transmitted or stored as three separate signals...
cables experienced problems displaying some Virtual Console games due to certain TV models/manufacturers not supporting 240p over a component video connection. Nintendo's solution was to implement 'Wii Component Cable Interlace Mode' which forces the emulator to output 480i instead of 240p, however many game released prior have still not been updated.
Resolutions
| Standard | Resolution |
|---|---|
| 240p | 320x240 |
| 360p | 640x360 |
Teleconferencing LDTV
Upcoming sources of LDTV using standard broadcasting techniques include mobile TV services powered by DVB-HDVB-H
DVB-H is one of three prevalent mobile TV formats. It is a technical specification for bringing broadcast services to mobile handsets. DVB-H was formally adopted as ETSI standard EN 302 304 in November 2004. The DVB-H specification can be downloaded from the official DVB-H website...
, DMB
Digital Multimedia Broadcasting
Digital Multimedia Broadcasting is a digital radio transmission technology developed in South Korea as part of the national IT project for sending multimedia such as TV, radio and datacasting to mobile devices such as mobile phones...
, or ATSC-M/H
ATSC-M/H
ATSC-M/H is a standard in the USA for mobile digital TV, that allows TV broadcasts to be received by mobile devices.....
. However, this kind of LDTV transmission technology is based on existent LDTV teleconferencing standards that have been in place for a decade or more.
See also
- Digital televisionDigital televisionDigital television is the transmission of audio and video by digital signals, in contrast to the analog signals used by analog TV...
- Digital audio broadcastingDigital audio broadcastingDigital Audio Broadcasting is a digital radio technology for broadcasting radio stations, used in several countries, particularly in Europe. As of 2006, approximately 1,000 stations worldwide broadcast in the DAB format....
- DVB, ATSC, ISDBISDBIntegrated Services Digital Broadcasting is a Japanese standard for digital television and digital radio used by the country's radio and television stations. ISDB replaced the previously used MUSE "Hi-vision" analogue HDTV system...
- SDTV, EDTVEdTVEDtv is a 1999 American comedy film directed by Ron Howard. An adaptation of the Quebec film Louis 19, le roi des ondes , it stars Matthew McConaughey, Jenna Elfman, Woody Harrelson, Ellen DeGeneres, Martin Landau, Rob Reiner, Sally Kirkland, Elizabeth Hurley, Clint Howard, and Dennis Hopper.The...
, HDTVHigh-definition televisionHigh-definition television is video that has resolution substantially higher than that of traditional television systems . HDTV has one or two million pixels per frame, roughly five times that of SD... - MPEG
- Handheld televisionHandheld televisionA Handheld television is a portable device that usually uses a TFT LCD or Organic light-emitting diode color display. Many of these devices resemble handheld transistor radios.-Hardware:...