Longman Dictionary of Contemporary English
n. 1 (context uncountable English) The broadcasting and receiving of television services via digital (rather than analog) signals, either broadcast, or via cable or satellite. 2 (context countable English) A television set that is capable of handling such signals.
Digital television (DTV) is the transmission of audio and video by digitally processed and multiplexed signal, in contrast to the totally analog and channel separated signals used by analog television. Digital TV can support more than one program in the same channel bandwidth. It is an innovative service that represents the first significant evolution in television technology since color television in the 1950s. Several regions of the world are in different stages of adaptation and are implementing different broadcasting standards. Below are the different widely used digital television broadcasting standards (DTB):
- Digital Video Broadcasting ( DVB) uses coded orthogonal frequency-division multiplexing ( OFDM) modulation and supports hierarchical transmission. This standard has been adopted in Europe, Australia and New Zealand.
- Advanced Television System Committee ( ATSC) uses eight-level vestigial sideband ( 8VSB) for terrestrial broadcasting. This standard has been adopted by six countries: United States, Canada, Mexico, South Korea, Dominican Republic and Honduras.
- Integrated Services Digital Broadcasting ( ISDB) is a system designed to provide good reception to fixed receivers and also portable or mobile receivers. It utilizes OFDM and two-dimensional interleaving. It supports hierarchical transmission of up to three layers and uses MPEG-2 video and Advanced Audio Coding. This standard has been adopted in Japan and the Philippines. ISDB-T International is an adaptation of this standard using H.264/MPEG-4 AVC that been adopted in most of South America and is also being embraced by Portuguese-speaking African countries.
- Digital Terrestrial Multimedia Broadcasting ( DTMB) adopts time-domain synchronous (TDS) OFDM technology with a pseudo-random signal frame to serve as the guard interval (GI) of the OFDM block and the training symbol. The DTMB standard has been adopted in the People's Republic of China, including Hong Kong and Macau.
- Digital Multimedia Broadcasting ( DMB) 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, laptops and GPS navigation systems.