Digital television (DTV) is the transmission of television signals using digital encoding, in contrast to the earlier analog television technology which used analog signals. At the time of its development it was considered an innovative advancement and represented the first significant evolution in television technology since color television in the 1950s. Modern digital television is transmitted in high-definition television (HDTV) with greater resolution than analog TV. It typically uses a widescreen aspect ratio in contrast to the narrower format (4:3) of analog TV. It makes more economical use of scarce radio spectrum space; it can transmit up to seven channels in the same bandwidth as a single analog channel, and provides many new features that analog television cannot. A transition from analog to digital broadcasting began around 2000. Different digital television broadcasting standards have been adopted in different parts of the world; below are the more widely used standards:
A television channel, or TV channel, is a terrestrial frequency or virtual number over which a television station or television network is distributed. For example, in North America, channel 2 refers to the terrestrial or cable band of 54 to 60 MHz, with carrier frequencies of 55.25 MHz for NTSC analog video (VSB) and 59.75 MHz for analog audio (FM), or 55.31 MHz for digital ATSC (8VSB). Channels may be shared by many different television stations or cable-distributed channels depending on the location and service provider
Digital Video Broadcasting (DVB) is a set of international open standards for digital television. DVB standards are maintained by the DVB Project, an international industry consortium, and are published by a Joint Technical Committee (JTC) of the European Telecommunications Standards Institute (ETSI), European Committee for Electrotechnical Standardization (CENELEC) and European Broadcasting Union (EBU).
Terrestrial television or over-the-air television (OTA) is a type of television broadcasting in which the content is transmitted via radio waves from the terrestrial (Earth-based) transmitter of a TV station to a TV receiver having an antenna. The term terrestrial is more common in Europe and Latin America, while in Canada and the United States it is called over-the-air or simply broadcast. This type of TV broadcast is distinguished from newer technologies, such as satellite television, in which the signal is transmitted to the receiver from an overhead satellite; cable television, in which the signal is carried to the receiver through a cable; and Internet Protocol television, in which the signal is received over an Internet stream or on a network utilizing the Internet Protocol. Terrestrial television stations broadcast on television channels with frequencies between about 52 and 600 MHz in the VHF and UHF bands. Since radio waves in these bands travel by line of sight, reception is generally limited by the visual horizon to distances of 64–97 kilometres (40–60 mi), although under better conditions and with tropospheric ducting, signals can sometimes be received hundreds of kilometers distant.
DVB-T, short for Digital Video Broadcasting – Terrestrial, is the DVB European-based consortium standard for the broadcast transmission of digital terrestrial television that was first published in 1997 and first broadcast in Singapore in February, 1998. This system transmits compressed digital audio, digital video and other data in an MPEG transport stream, using coded orthogonal frequency-division multiplexing modulation. It is also the format widely used worldwide for Electronic News Gathering for transmission of video and audio from a mobile newsgathering vehicle to a central receive point. It is also used in the US by Amateur television operators.
A subcarrier is a sideband of a radio frequency carrier wave, which is modulated to send additional information. Examples include the provision of colour in a black and white television system or the provision of stereo in a monophonic radio broadcast. There is no physical difference between a carrier and a subcarrier; the "sub" implies that it has been derived from a carrier, which has been amplitude modulated by a steady signal and has a constant frequency relation to it.
Integrated Services Digital Broadcasting is a Japanese broadcasting standard for digital television (DTV) and digital radio.
Advanced Television Systems Committee (ATSC) standards are an International set of standards for broadcast and 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, South Korea and Trinidad & Tobago. Several former NTSC users, such as Japan, have not used ATSC during their digital television transition, because they adopted other systems such as ISDB developed by Japan, and DVB developed in Europe, for example.
Digital radio is the use of digital technology to transmit or receive across the radio spectrum. Digital transmission by radio waves includes digital broadcasting, and especially digital audio radio services.
Broadcasttelevision systems are the encoding or formatting systems for the transmission and reception of terrestrial television signals.
Digital terrestrial television is a technology for terrestrial television where television stations broadcast television content in a digital format. DTTV is a major technological advance over analog television, and has largely replaced analog television broadcast, which had been in common use since the middle of the 20th century. Test broadcasts began in 1998 with the changeover to DTTV, also known as the Analog Switchoff (ASO) or Digital Switchover (DSO), which began in 2006 and is now complete in many countries. The advantages of digital terrestrial television are similar to those obtained by digitizing platforms such as cable TV, satellite, and telecommunications: more efficient use of radio spectrum bandwidth, provision of more television channels than analog, better quality images, and potentially lower operating costs for broadcasters.
Free-to-air (FTA) services are television (TV) and radio services broadcast in unencrypted form, allowing any person with the appropriate receiving equipment to receive the signal and view or listen to the content without requiring a subscription, other ongoing cost, or one-off fee. In the traditional sense, this is carried on terrestrial radio signals and received with an antenna.
Digital terrestrial television in the United Kingdom encompasses over 100 television, radio and interactive services broadcast via the United Kingdom's terrestrial television network and receivable with a standard television set. The majority of digital terrestrial television (DTT) services, including the five former analogue channels, are broadcast free-to-air, and a further selection of encrypted pay TV services are also available.
In broadcasting, digital subchannels are a method of transmitting more than one independent program stream simultaneously from the same digital radio or television station on the same radio frequency channel. This is done by using data compression techniques to reduce the size of each individual program stream, and multiplexing to combine them into a single signal. The practice is sometimes called "multicasting".
IP over DVB implies that Internet Protocol datagrams are distributed using some digital television system, for example DVB-H, DVB-SH, DVB-T, DVB-S, DVB-C or their successors like DVB-T2, DVB-S2, and DVB-C2. This may take the form of IP over MPEG, where the datagrams are transferred over the MPEG transport stream, or the datagrams may be carried in the DVB baseband frames directly, as in GSE.
ATSC-M/H is a U.S. standard for mobile digital TV that allows TV broadcasts to be received by mobile devices.
A free-to-air or FTA Receiver is a satellite television receiver designed to receive unencrypted broadcasts. Modern decoders are typically compliant with the MPEG-2/DVB-S and more recently the MPEG-4/DVB-S2 standard for digital television, while older FTA receivers relied on analog satellite transmissions which have declined rapidly in recent years.
Saorview is the national digital terrestrial television (DTT) service in Ireland. It is owned by RTÉ and operated by 2RN.
Satellite subcarrier audio is audio transmitted by way of satellite that uses a separate analog or digital signal carried on a main radio transmission on a specific satellite transponder. More technically, it is an already-modulated signal, which is then modulated into another signal of higher frequency and bandwidth. In a more general sense, satellite subcarrier audio is an early form of satellite radio not intended for the consumer market but was initially unencrypted, thus receivable to satellite hobbyists.
