Digital television transition in the context of "Digital terrestrial television"

Digital television (DTV) is the transmission of television signals using digital encoding, in contrast to the earlier analog television technology which used analog signals. In the 2000s it was represented as 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 (commonly 16:9) 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:

• Digital Video Broadcasting (DVB) uses coded orthogonal frequency-division multiplexing (OFDM) modulation and supports hierarchical transmission. This standard has been adopted in Europe, Africa, Asia and Australia, for a total of approximately 60 countries.
• Advanced Television System Committee (ATSC) standard uses eight-level vestigial sideband (8VSB) for terrestrial broadcasting. This standard has been adopted by 9 countries: the United States, Canada, Mexico, South Korea, Bahamas, Jamaica, the Dominican Republic, Haiti and Suriname.
• Integrated Services Digital Broadcasting (ISDB) is a system designed to provide good reception to fixed receivers and also portable or mobile receivers utilizing 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, which has been adopted in most of South America as well as Botswana and Angola. 1seg (1-segment) is a special form of ISDB. Each channel is further divided into 13 segments. Twelve are allocated for HDTV and the other for narrow-band receivers such as mobile televisions and cell phones.
• Digital Terrestrial Multimedia Broadcast (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 China, including Hong Kong and Macau.
• Digital Multimedia Broadcasting (DMB) is a digital radio transmission technology developed and adopted in South Korea as part of the national information technology project for sending multimedia such as TV, radio and datacasting to mobile devices such as mobile phones, laptops and GPS navigation systems.

Phase Alternating Line (PAL) is a colour encoding system for analogue television. It was one of three major analogue colour television standards, the others being NTSC and SECAM. In most countries it was broadcast at 625 lines, 50 fields (25 frames) per second, and associated with CCIR analogue broadcast television systems B, D, G, H, I and K. The articles on analogue broadcast television systems further describe frame rates, image resolution, and audio modulation.

PAL video is composite video because luminance (luma, monochrome image) and chrominance (chroma, colour applied to the monochrome image) are transmitted together as one signal. A latter evolution of the standard, PALplus, added support for widescreen broadcasts with no loss of vertical image resolution, while retaining compatibility with existing sets. Almost all of the countries using PAL are currently in the process of conversion, or have already converted transmission standards to DVB, ISDB or DTMB. The PAL designation continues to be used in some non-broadcast contexts, especially regarding console video games where it is referring to the markets other than North America and Japan.

SECAM, also written SÉCAM (French pronunciation: [sekam],Système Électronique Couleur Avec Mémoire, French for electronic colour system with memory), is an analogue colour television system that was used in France, Russia, and some other countries or territories of Europe and Africa. It was one of three major analog colour television standards, the others being PAL and NTSC. Like PAL, a SECAM picture is also made up of 625 interlaced lines and is displayed at a rate of 25 frames per second (except SECAM-M). However, due to the way SECAM processes colour information, it is not compatible with the PAL video format standard. SECAM video is composite video; the luminance (luma, monochrome image) and chrominance (chroma, color applied to the monochrome image) are transmitted together as one signal.

All the countries using SECAM have either converted to Digital Video Broadcasting (DVB), the new pan-European standard for digital television, or are currently in the process of conversion. SECAM remained a major standard into the 2000s.

The following tables show the frequencies assigned to analog broadcast television channels in various regions of the world, along with the ITU letter designator for the transmission system used. The frequencies shown are for the channel limits and for the analog video and audio carriers. The channel itself usually occupies 6, 7 or 8 megahertz of bandwidth depending on the television transmission system in use. For example, North American channel 1 occupies the spectrum from 44 to 50 MHz. See Broadcast television systems for a table of signal characteristics, including bandwidth, by ITU letter designator. Analog television broadcasts have been phased out in most regions, having been replaced by digital television broadcasts.

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. Like NTSC, ATSC is used mostly in the United States, Mexico, Canada, South Korea, and Trinidad and Tobago. Several former NTSC users like Japan have not used ATSC during their digital television transition, because they adopted other systems like ISDB developed by Japan and DVB developed in Europe, for example.

The ATSC standards were developed in the early 1990s by the Grand Alliance, a consortium of electronics and telecommunications companies that assembled to develop a specification for what is now known as HDTV. The standard is now administered by the Advanced Television Systems Committee. It includes a number of patented elements, and licensing is required for devices that use these parts of the standard. Key among these is the 8VSB modulation system used for over-the-air broadcasts. ATSC 1.0 technology was primarily developed with patent contributions from LG Electronics, which held most of the patents for the ATSC standard.