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Digital Video Broadcasting (DVB) is an organization that promotes internationally accepted standards for digital television, especially for HDTV and satellite TV and data communications via satellite (one-way, called DVB-IP, and bidirectional, called DVB-RCS ).
The access way is not broadband, as it is done by combining traditional Internet access via PSTN / ISDN modem plus univía DVB satellite access.
Principles of the DVB
The DVB (Digital Video Broadcasting) is an agency to create and propose the standardization procedures for digital TV compatible. It consists of more than 270 institutions and companies around the world. The proposed standards have been widely accepted in Europe and almost every continent, with the exception of the United States, Canada and Japan where they coexist with other proprietary systems. All procedures for coding video and audio sources are based on standards defined by MPEG. However, we have seen that the MPEG standards only cover the issues and methodologies used in the compression of audio and video signals and procedures multiplexing and synchronization of these signals into frames of the program or transportation. Once defined the transport stream is necessary to define the signal modulation schemes to be used for different types of broadcast (satellite, cable and terrestrial), the types of codes error protection and conditional access mechanisms to services and programs.
The DVB has developed different standards depending on the characteristics of the broadcasting system. The most widely used standards today are the DVB-S and DVB-C transmissions that provide digital television signals by satellite networks and cable distribution, respectively. The transmission of digital television via terrestrial distribution networks using conventional UHF channels foreseen in the DVB-T, currently being implemented in most European countries. In addition to these standards are also specified distribution systems for digital television signals in multipoint networks, systems, SMATV (Satellite Master Antenna Television). There are also standards that define the characteristics of the signal on the return channel for interactive TV systems, the data structure for the encryption and decryption of conditional access programs, the transmission of subtitles, and broadcasting data (new teletext channels) using 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 mobile devices (DVB-H)
Satellite TV for handheld devices (DVB-SH)
These standards define the physical layer and data link layer of a distribution system. The devices interact with the physical layer via a synchronous parallel interface (SPI), synchronous serial interface (SSI) or an asynchronous serial interface (ASI). All data is transmitted in transport streams MPEG-2 with some additional constraints (DVB-MPEG). Is being piloted in several countries a standard for distributing compressed in time (DVB-H) for distribution to mobile devices.
These standards mainly differ in the types of modulation used, due to various technical restrictions:
DVB-S (SHF) uses QPSK, 8PSK or 16-QAM
DVB-S2 (SHF) uses QPSK, 8PSK, 16APSK or 32APSK in the relays.
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 hierarchical modulation support.
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 protocol independent).
To facilitate the 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, for example, DVB-SUB for subtitles.
Relationship with other standards
While DVB is the most universal standard for the transmission and reception of digital television is not the only one, are also available in the international market of U.S. origin ATSC and ISDB from Japan, mainly in the form of TV digital Terrestrial.
Adoption
DVB-S and DVB-C were ratified in 1994. DVB-T was ratified in early 1997. The first commercial DVB-T broadcasts were performed by the United Kingdom's Digital TV Group in late 1998. In 2003 Berlin, Germany was the first area to completely stop broadcasting analog TV signals. Many European countries aim to be fully covered with digital television by 2010 and switch off PAL/SECAM services by then.
As of 2005, DVB-T television sets are not significantly more expensive than analog television sets. Most popular in Europe are the set-top boxes that enable DVB-T to be received through an ordinary analogue television, with the price dropping remarkably in 2007.
In its origin Europe, in Australia, South Africa and India DVB is used throughout the areas it covers or is at least decided to be. This also holds true for cable and satellite in most Asian, African and many South American countries. Many of these have not yet selected a format for digital terrestrial broadcasts (DTTV) and a few (Canada, El Salvador, Honduras, Mexico, South Korea and the United States) chose ATSC instead of DVB-T.
The access way is not broadband, as it is done by combining traditional Internet access via PSTN / ISDN modem plus univía DVB satellite access.
Principles of the DVB
The DVB (Digital Video Broadcasting) is an agency to create and propose the standardization procedures for digital TV compatible. It consists of more than 270 institutions and companies around the world. The proposed standards have been widely accepted in Europe and almost every continent, with the exception of the United States, Canada and Japan where they coexist with other proprietary systems. All procedures for coding video and audio sources are based on standards defined by MPEG. However, we have seen that the MPEG standards only cover the issues and methodologies used in the compression of audio and video signals and procedures multiplexing and synchronization of these signals into frames of the program or transportation. Once defined the transport stream is necessary to define the signal modulation schemes to be used for different types of broadcast (satellite, cable and terrestrial), the types of codes error protection and conditional access mechanisms to services and programs.
The DVB has developed different standards depending on the characteristics of the broadcasting system. The most widely used standards today are the DVB-S and DVB-C transmissions that provide digital television signals by satellite networks and cable distribution, respectively. The transmission of digital television via terrestrial distribution networks using conventional UHF channels foreseen in the DVB-T, currently being implemented in most European countries. In addition to these standards are also specified distribution systems for digital television signals in multipoint networks, systems, SMATV (Satellite Master Antenna Television). There are also standards that define the characteristics of the signal on the return channel for interactive TV systems, the data structure for the encryption and decryption of conditional access programs, the transmission of subtitles, and broadcasting data (new teletext channels) using 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 mobile devices (DVB-H)
Satellite TV for handheld devices (DVB-SH)
These standards define the physical layer and data link layer of a distribution system. The devices interact with the physical layer via a synchronous parallel interface (SPI), synchronous serial interface (SSI) or an asynchronous serial interface (ASI). All data is transmitted in transport streams MPEG-2 with some additional constraints (DVB-MPEG). Is being piloted in several countries a standard for distributing compressed in time (DVB-H) for distribution to mobile devices.
These standards mainly differ in the types of modulation used, due to various technical restrictions:
DVB-S (SHF) uses QPSK, 8PSK or 16-QAM
DVB-S2 (SHF) uses QPSK, 8PSK, 16APSK or 32APSK in the relays.
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 hierarchical modulation support.
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 protocol independent).
To facilitate the 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, for example, DVB-SUB for subtitles.
Relationship with other standards
While DVB is the most universal standard for the transmission and reception of digital television is not the only one, are also available in the international market of U.S. origin ATSC and ISDB from Japan, mainly in the form of TV digital Terrestrial.
Adoption
DVB-S and DVB-C were ratified in 1994. DVB-T was ratified in early 1997. The first commercial DVB-T broadcasts were performed by the United Kingdom's Digital TV Group in late 1998. In 2003 Berlin, Germany was the first area to completely stop broadcasting analog TV signals. Many European countries aim to be fully covered with digital television by 2010 and switch off PAL/SECAM services by then.
As of 2005, DVB-T television sets are not significantly more expensive than analog television sets. Most popular in Europe are the set-top boxes that enable DVB-T to be received through an ordinary analogue television, with the price dropping remarkably in 2007.
In its origin Europe, in Australia, South Africa and India DVB is used throughout the areas it covers or is at least decided to be. This also holds true for cable and satellite in most Asian, African and many South American countries. Many of these have not yet selected a format for digital terrestrial broadcasts (DTTV) and a few (Canada, El Salvador, Honduras, Mexico, South Korea and the United States) chose ATSC instead of DVB-T.