Digital Video Broadcasting

Digital Video Broadcasting (DVB) is an organization that promotes internationally accepted digital television standards, especially for HDTV and broadcast television. satellite, as well as for data communications via satellite (one-way, called DVB-IP, and two-way, called DVB-RCS).

One-way access is not broadband, since it is done by combining traditional Internet access, via RTB/ISDN, plus the single-way DVB satellite access modem.

History of the DVB project

It was created in 1993 as a result of an alliance between several European private companies that sought to standardize the work that had been done on digital television. Thus, new standards were created in a sector such as digital broadcasting, which until then was impractical and expensive.

In this way, a process began in which companies from all over the world were quickly added to end up jointly creating and developing the different 'DVB' . The first agreed system was DVB-S (satellite transmission) in 1994, which was used by a French operator shortly thereafter. The same year DVB-C (cable transmission) appeared, while the DVB-T system (terrestrial transmission) was later emerging in 1997. The first terrestrial broadcasts were in 1998 in Sweden and the United Kingdom.

In this way, the DVB open standards became a benchmark, being used by almost everyone related to the sector. Currently the organization is made up of some 270 organizations and companies from 30 countries.

DVB principles

DVB is an organization in charge of creating and proposing standardization procedures for compatible digital television. It is made up of more than 270 institutions and companies from around the world. The proposed standards have been widely accepted in Europe and almost all continents, with the exception of the United States, Canada and Japan where they coexist with other proprietary systems. All encoding procedures for video and audio sources are based on the standards defined by MPEG. However, we have seen that the MPEG standards only cover the aspects and methodologies used in the compression of audio and video signals and the procedures for multiplexing and synchronizing these signals in program or transport frames. Once the transport frame has been defined, it is necessary to define the signal modulation systems that will be used for the different types of broadcasting (satellite, wired and terrestrial), the types of protection codes against errors and the mechanisms for conditional access to the data. services and programs.

DVB has developed different standards depending on the characteristics of the broadcasting system. The most widely used standards today are DVB-S and DVB-C, which contemplate the transmission of digital television signals through satellite distribution networks and video cable, respectively. The transmission of digital television through terrestrial distribution networks using conventional UHF channels is contemplated in the DVB-T standard, which is currently being implemented in most European countries. In addition to these standards, systems for the distribution of digital television signals in multipoint networks, Satellite Master Antenna Television (SMATV) systems, are also specified. There are also standards that define the characteristics of signaling in the return channel in interactive television systems, the data transmission structure for the encryption and decryption of conditional access programs, the transmission of subtitles, and the broadcasting of data (new teletext channels) through digital systems.

Transmission

DVB systems distribute data by:

• satellite (DVB-S and DVB-S2)
• cable (DVB-C and DVB-C2)
• terrestrial television (DVB-T and DVB-T2)
• terrestrial television for portable devices (DVB-H)
• Satellite television for portable devices (DVB-SH)
• terrestrial television and Internet for portable devices (DVB-I) [1]

These standards define the physical layer and the data link layer of a distribution system. Devices interact with the physical layer through a Synchronous Parallel Interface (SPI), a Synchronous Serial Interface (SSI), or an Asynchronous Serial Interface (ASI). All data is transmitted in MPEG-2 transport streams with some additional restrictions (DVB-MPEG). A standard for time-compressed distribution (DVB-H) for distribution to mobile devices is being tested in several countries.

These standards differ mainly in the types of modulation used, due to different technical constraints:

• DVB-S (SHF) uses QPSK, 8PSK or 16-QAM.
• DVB-S2 (SHF) uses QPSK, 8PSK, 16APSK or 32APSK in the transmitters.
• DVB-C (VHF/UHF) uses QAM, 16-QAM, 32-QAM, 64-QAM, 128-QAM or 256-QAM (64-QAM, in general).
• DVB-T (VHF/UHF) 16-QAM or 64-QAM (or QPSK) in combination with COFDM and supports hierarchical modulation.
• DVB-I [2]

Content

In addition to audio and video transmission, DVB also defines data connections (DVB-DATA - EN 301 192) with return channels (DVB-RC) for different media (DECT, GSM, PSTN/ISDN, satellite, etc.) and protocols (DVB-IPTV: Internet Protocol; DVB-NPI: Network Independent Protocol).

To facilitate conversion, these standards also support existing technologies such as teletext (DVB-TXT) and vertical sync (DVB-VBI). However, for many applications, more advanced alternatives are available, such as DVB-SUB for subtitles.

Relation to other standards

Although DVB is the most universal standard for the transmission and reception of digital television, the standards are also available in the international market: ATSC of American origin, and ISDB of Japanese origin, mainly in the Digital Terrestrial Television format.