Digital television (DTV) uses digital modulation and compression to broadcast video, audio and data signals to television sets. Modulation is the process of varying a carrier signal, typically a sinusoidal signal, in order to use that signal to convey information. ...

Introduction

A major use of DTV can be to carry more channels in the same amount of bandwidth. Another can be high definition programming. The digital signal eliminates common analog broadcasting artifacts such as "ghosting", "snow" and static noises in audio. It can replace them with new MPEG compression artifacts, such as "blocking", when transmitted at too low a data rate, and may fail to work entirely in situations where analog television would have produced an impaired but watchable picture. Depending on the sophistication and level of the error correction defined by the standard and chosen by the broadcaster, DTV may either work perfectly or not work at all. When used as a specific technical term used to distinguish from standard definition television in the context of High Definition Television (HDTV) the term high definition has become associated with a particular set of technical specifications or with the values of certain parameters within such specifications. ... The Moving Picture Experts Group (MPEG) is a working group of ISO/IEC charged with the development of video and audio encoding standards. ... In telecommunication, data signaling rate (DSR) is the aggregate rate at which data pass a point in the transmission path of a data transmission system. ...

The switch-over to DTV systems often coincides with a change in picture format from an aspect ratio of 4:3 to one of 16:9. This enables TV to get closer to the aspect ratio of movies and human vision. On traditional screens this leads to "letterbox" black bars above and below the picture due to placing the 16:9 picture in a 4:3 frame. The previous aspect ratio of 4:3 was chosen to match the Academy standard ratio of the day. The aspect ratio of an image is its displayed width divided by its height (usually expressed as x:y). For instance, the aspect ratio of a traditional television screen is 4:3, or 1. ... Film refers to the celluloid media on which movies are printed Film is a term that encompasses motion pictures as individual projects, as well as the field in general. ... The Academy of Motion Picture Arts and Sciences (AMPAS) is a professional honorary organization, founded on May 11, 1927 in California to advance the arts and sciences of motion pictures. ...

Market

Terrestrial

Digital terrestrial television (DTT) is in the process of deployment in a number of countries.

• Governments see DTT as a "futuristic" technology that will push their country to the forefront of the "digital revolution" and free up existing TV frequencies for resale, for example to communications operators.
• Broadcasters see DTT as a way to fight competition from satellite and cable DTV and other digital program distribution technologies, such as personal digital video recorders (PVR) and video on demand (VoD).
• Hardware manufacturers see DTT as a way to sell set-top boxes first and new all-in-one TV sets later.
• Consumers see DTT as a way to obtain more programs from their existing TV antenna at the cost of a set-top box or new television.

In some countries, DTT is seen as a technology that is being pushed on a public that does not exhibit much demand for it. This is particularly so in countries where high definition programs are broadcast terrestrially, since HDTV sets are at the moment prohibitively expensive, and very little HDTV content exists apart from movies. The Digital Revolution is a term describing the effects of the rapid drop in cost and rapid expansion of power of digital devices such as computers and telecommunications. ... The personal video recorder (PVR), also called digital video recorder (DVR), is a consumer electronics device that records television shows to a hard disk in digital format. ... Video on demand systems are systems which allow users to select and watch video content over a network as part of an interactive television system. ... When used as a specific technical term used to distinguish from standard definition television in the context of High Definition Television (HDTV) the term high definition has become associated with a particular set of technical specifications or with the values of certain parameters within such specifications. ...

Satellite

DTV has been shown to be commercially viable in the satellite television market, where it is used to multiplex large numbers of channels onto the available bandwidth. The business model for satellite DTV in the US and the UK is similar to that for cable TV. Satellite DTV operators tend to act as packagers for large numbers of channels, including pay-TV. The greater RF bandwidth available to satellite operators allows them to out-compete terrestrial DTV operators on both number of channels and picture quality. Wikiquote has a collection of quotations by or about: United States Wikinews has news related to this article: United States United States government Official website of the United States government - Gateway to governmental sites White House - Official site of the US President Senate. ... Cable television or Community Antenna Television (CATV) (and often shortened to cable) is a system of providing television, FM radio programming and other services to consumers via radio waves transmitted directly to people’s televisions through fixed coaxial cables as opposed to the over-the-air method used in traditional... Rf or RF may stand for: Radio frequency, a term in broadcasting Right field(er), a defensive position in baseball Rutherfordium (Rf), symbol for the chemical element RF, rheumatoid factor RF, a Mazda piston engine The Russian Federation This is a disambiguation page — a navigational aid which lists other pages...

Cable

Where an original analogue cable set-top box is already required this has to be replaced to recieve Digital cable. From a users point of view the main advantage appears to be simply better picture quality and more channel availability, however (depending on the choices operators make regarding set top box hardware and middleware software) many other features become possible with the transfer away from analogue. Often a TV guide (7 day schedules) with extended information can be viewed, reminders to watch programmes can be set and advanced parental censorship on channel content can be exercised. Operators also enjoy better CA (conditional access) on Digitally transmitted streams as they can be sent 'encrypted' with schemes such as DES encryption to help prevent unauthorised access and protect revenues.

Operators wishing to increase the carrying capacity of their original networks have to replace all analogue set top boxes with digital replacements before turning off the analogue feeds, this is not a trivial or low cost solution as literally millions of set top boxes require replacement.

Some of the more advanced cable networks even have the use of a return path (a 2 way data communications path to allow DTV set top boxes to return information back to the operators head-end). This allows them to extend services offered to include interactive web style content viewing, gaming, voting and other 'on demand' services such as control of Video On Demand films.

IPTV

Internet technologies are finally starting to be adapted for use with DTV deployments, meaning a single broadband internet connection will eventually service your home providing you with Triple Play (Voice Over IP, Internet and Digital Television).

IPTV is a big step forward when combined with the latest advancements in picture quality such as High Definition (HDTV) and new AVC (Advanced Video Compression) stardards such as MPEG4 H.264 or WM9 (very efficient picture emerging compression standards).

Not only are Set Top Boxes becoming smarter (they are essentially cut down PC's in their own right) they will interact with other devices such as PDA's, mobile phones and the internet to provide a truly flexible solution allowing local information to be tailored to specific regions (e.g. weather and news from your local area).

Analog switch-off

In general, viewers who are happy with their existing analog TV systems tend not to adopt terrestrial DTV systems (so-called "digital refuseniks"). Many of those who want cable-TV-like services will either buy cable TV, where available, or satellite DTV.

Governments are responding to this with an attempt to force the issue by enforcing planned "switch-off" dates for analog television, but are encountering resistance from the public, as they fear that this will mean that they will need to replace every television they own, including portable TVs and bedroom TVs, or buy additional digital receivers.

Technical

Formats

All digital TV variants can carry both standard definition television (SDTV) and high definition television (HDTV). ... High-definition television (HDTV) means broadcast of television signals with a higher resolution than traditional formats (NTSC, SECAM, PAL) allow. ...

All early SDTV television standards were analog in nature, and SDTV digital television systems derive much of their structure from the need to be compatible with analog television. In particular, the interlaced scan is a legacy of analog television. Analog television encodes picture information by varying the voltages and/or frequency of the signal. ... Interlacing is a method of displaying images on a raster-scanned display device, such as a cathode ray tube (CRT). ...

Attempts were made during the development of digital television to prevent a repeat of the fragmentation of the global market into different standards (that is, PAL, SECAM, NTSC). However, the world could not agree on a single standard, and hence there are two major standards in existence: the European DVB system and the U.S. ATSC system, plus the Japanese system ISDB. For other meanings of PAL see PAL (disambiguation). ... SÉCAM (Séquentiel couleur à mémoire, French for sequential colour with memory) is an analog color television system first used in France. ... NTSC is the analog television system in use in the United States and some other places, mostly the Americas (see map). ... A satellite composite image of Europe Europe is geologically and geographically a peninsula, forming the westernmost part of Eurasia. ... DVB, short for Digital Video Broadcasting, is a suite of internationally accepted, open standards for digital television maintained by the DVB Project, an industry consortium with more than 300 members, and published by a Joint Technical Committee (JTC) of European Telecommunications Standards Institute (ETSI), European Committee for Electrotechnical Standardization (CENELEC... Wikiquote has a collection of quotations by or about: United States Wikinews has news related to this article: United States United States government Official website of the United States government - Gateway to governmental sites White House - Official site of the US President Senate. ... The Advanced Television Systems Committee (ATSC) is the group that helped to develop the new digital television standard for the United States, also adopted by Canada, Mexico and South Korea and being considered by other countries. ... Integrated Services Digital Broadcasting (ISDB) is the digital television (DTV) and digital audio broadcasting (DAB) format. ...

Most countries in the world have adopted DVB, but several have followed the U.S. in adopting ATSC instead (Canada, Mexico, South Korea). Korea has adopted ISDB for satellite mobile broadcasting.

There could be other specialized high-resolution digital video formats in the future for markets other than home entertainment. Ultra High Definition Video (UHDV) is a format proposed by NHK of Japan that provides a resolution 16 times greater than HDTV. Ultra High Definition Video or UHDV is a digital video format, currently proposed by NHK of Japan. ... NHK NHK (日本放送協会, Nippon Hōsō Kyōkai), or Japan Broadcasting Corporation, is Japans public broadcaster. ...

Bandwidth

In current practice, HDTV uses 1280 × 720 pixels in progressive scan mode (abbreviated 720p) or 1920 × 1080 pixels in interlace mode (1080i). SDTV has less resolution (640 x 480 or 704 × 480 pixels with NTSC, 768 × 576 or 1024 × 576 with PAL in 4:3 and 16:9 aspect ratios respectively), but allows the bandwidth of a DTV channel (or "multiplex") to be subdivided into multiple sub-channels. The TV stations can use subchannels to carry multiple broadcasts of video, audio, or any other data, and can distribute their so-called "bit budget" as necessary, such as dropping one sub-channel down to a lower resolution in order to make another one available to show a wide-screen movie. Often, this is done automatically, using a statistical multiplexer (or "stat-mux"). This article needs to be cleaned up to conform to a higher standard of quality. ... Progressive scanning is a method for representing moving images on a display screen, where every pixel is represented in each frame. ... Interlacing is a method of displaying images on a raster-scanned display device, such as a cathode ray tube (CRT). ... NTSC is the analog television system in use in the United States and some other places, mostly the Americas (see map). ... For other meanings of PAL see PAL (disambiguation). ... A Statistical Multiplexer allows broadcasters to change the bitrate of channels according to the channels needs. ...

Multiplexes can even reduce their overall bit budget and digital bandwidth, in order to reduce the transmission bitrate and make reception easier for more distant or mobile viewers. // Analog For analog signals, bandwidth is the width, usually measured in hertz, of a frequency band f2 − f1. ... In telecommunications and computing, bit rate (sometimes written bitrate) is the frequency at which bits are passing a given (physical or metaphorical) point. It is quantified using the bit per second (bit/s) unit. ...

Reception

Today most viewers receive digital television via a set-top box, which decodes the digital signals into signals that analog televisions can understand, but a slowly growing number of TV sets with integrated receivers are already available. Access to channels can be controlled by a removable smart card, for example via the Common Interface (CI) standard. Some signals carry encryption and specify use conditions (such as "may not be recorded" or "may not be viewed on displays larger than 1m in diagonal measure") backed up with the force of law under the WIPO Copyright Treaty and national legislation implementing it, such as the U.S. Digital Millennium Copyright Act. A decoder is a device which does the reverse of an encoder, undoing the encoding so that the original information can be retrieved. ... A smartcard or smart card is a tiny secure cryptoprocessor embedded within a credit card-sized or smaller (like the GSM SIM) card. ... In cryptography, encryption is the process of obscuring information to make it unreadable without special knowledge. ... The WIPO Copyright Treaty, adopted by the World Intellectual Property Organization (WIPO) in 1996, provides additional protections for copyright deemed necessary in the modern information era. ... Legislation refers 1. ... The Digital Millennium Copyright Act (DMCA) is a controversial United States copyright law. ...

Interaction

Digital teletext is an enhanced teletext service based on XHTML and CSS. Many countries, including Finland, use Multimedia Home Platform DVB-MHP for digital teletext. An alternative is the MHEG-5 platform used terrestrially in the UK. Digital teletext is supposed to provide interactive services, but for this a separate "return path", such as a telephone line or Internet connection, is required. Teletext is an information retrieval service provided by television broadcast companies. ... Extensible Hypertext Markup Language, or XHTML, is a markup language that has the same expressive possibilities as HTML, but a stricter syntax. ... In computing, Cascading Style Sheets (CSS) is a stylesheet language used to describe the presentation of a document written in a markup language. ... Multimedia Home Platform (DVB-MHP) is an open middleware system standard designed by the DVB project for interactive digital television. ... MHEG-5 is a standard devised for the middleware of digital teletext services in the United Kingdom. ... A telephone handset A touch-tone telephone dial Telephone Complex relay used in a telephone switching system. ...

ISDB has adopted ARIB STD-B24 for interactive services. ISDB has labeled interactive services as data broadcasting. ARIB STD-B24 system is based on BML. BML is modified XML language for data broadcasting. ISDB has been providing EPG, news, weather forecast, traffic information, stock market conditions, educational program, interactive game program, TV shopping via the Internet, etc. Integrated Services Digital Broadcasting (ISDB) is the digital television (DTV) and digital audio broadcasting (DAB) format. ... The Association of Radio Industries and Businesses, commonly known as ARIB, is a standardization organization in Japan. ... Datacasting is the broadcasting of data over a wide area via radio waves. ... BML is a TLA that could mean: Bean markup language Belfast and Moosehead Lake Railroad – AAR reporting mark BML Better markup language Bibliothèque Médicale AF Lemanissier [1] Bodega Marine Laboratory [2] at the University of California, Davis Bramhall station – see UK railway stations - B Bytown Marine Limited [3] This is... BML is a TLA that could mean: Bean markup language Belfast and Moosehead Lake Railroad – AAR reporting mark BML Better markup language Bibliothèque Médicale AF Lemanissier [1] Bodega Marine Laboratory [2] at the University of California, Davis Bramhall station – see UK railway stations - B Bytown Marine Limited [3] This is... The Extensible Markup Language (XML) is a W3C-recommended general-purpose markup language for creating special-purpose markup languages. ... An electronic program (or programme) guide, or EPG, is a program schedule, typically broadcast alongside digital television or radio signals. ... NEWS was a line of Sony Unix workstations sold from 1987 until around 1996. ... BBCs Alex Deakin presenting a weather report. ... A game is a recreational activity involving one or more players. ...

Deployment

List of digital television deployments by country The transition to Digital television is a process that follows different paces around the world. ...

See also

• Broadcast television systems
• Interactive television
• LinuxTV
• List of digital television terms
• Multimedia Home Platform (MHP)
• Set-top box (STB)
• system-on-chip (SoC)
• High-definition television
• ATSC,DVB,ISDB