DVB

DVB, short for Digital Video Broadcasting, is a suite of internationally accepted, open standards for digital television maintained by the DVB Project, an industry consortium with more than 270 members, and published by a Joint Technical Committee (JTC) of European Telecommunications Standards Institute (ETSI), European Committee for Electrotechnical Standardization (CENELEC) and European Broadcasting Union (EBU). The standards can be obtained for free at the ETSI website after registration.

How the several DVB sub-standards interact is described in the DVB Cookbook (DVB-Cook).

Transmission

DVB systems distribute data by:

satellite (DVB-S and DVB-S2)
cable (DVB-C)
terrestrial television (DVB-T)
terrestrial television for handhelds (DVB-H)

These standards define the physical layer and data link layer of a distribution system. Devices interact with the physical layer via a synchronous parallel interface (SPI), synchronous serial interface (SSI), or asynchronous serial interface (ASI). All data is transmitted in MPEG-2 transport streams with some additional constraints (DVB-MPEG). A standard for temporally compressed distribution to mobile devices (DVB-H) under development.

These distribution systems differ mainly in the modulation schemes used, due to the different technical constraints:

DVB-S (SHF) uses QPSK
- DVB-S2 uses QPSK, 8PSK, 16APSK or 32APSK, at the broadcasters decision. QPSK and 8PSK are the only versions regularly used.
DVB-C (VHF/UHF) uses QAM: 64-QAM or 256-QAM
DVB-T (VHF/UHF) uses 16-QAM or 64-QAM (or QPSK) in combination with COFDM

Content

Besides audio and video transmission, DVB also defines data connections (DVB-DATA - EN 301 192) with return channels (DVB-RC) for several media (DECT, GSM, PSTN/ISDN, satellite etc.) and protocols (DVB-IPI: Internet Protocol; DVB-NPI: network protocol independent).

Legacy technologies like teletext (DVB-TXT) and vertical blanking interval data (DVB-VBI) are also supported by the standards to ease conversion. However for many applications more advanced alternatives like DVB-SUB for sub-titling are available.

Encryption and metadata

The conditional access system (DVB-CA) defines a common scrambling algorithm (DVB-CSA) and a common interface (DVB-CI) for accessing scrambled content. DVB system providers develop their proprietary conditional access systems within these specifications. DVB transports include metadata called service information (DVB-SI) that links the various elementary streams into coherent programs and provides human-readable descriptions for electronic program guides.

DVB is also developing a Content Protection and Copy Management system for protecting content after it has been received (DVB-CPCM), which is intended to allow flexible use of recorded content on a home network or beyond, while preventing unconstrained sharing on the Internet.

Software platform

The DVB Multimedia Home Platform (DVB-MHP) defines a Java-based platform for the development of consumer video system applications. In addition to providing abstractions for many DVB and MPEG-2 concepts, it provides interfaces for other features like network card control, application download, and layered graphics.

Return channel

DVB has standardised a number of return channels that work together with DVB(-S/T/C) to create bi-directional communication. RCS is short for Return Channel Satellite, and specifies return channels in C, Ku and Ka frequency-bands with return bandwidth of up to 2 Mbit/s. DVB-RCT is short for Return Channel Terrestrial, specified by ETSI EN 301958

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 Terrestrial Group (DTG) 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.

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, Mexico and South Korea) chose ATSC instead of DVB-T for now. In Malaysia, a new Pay-TV station MiTV began service in September 2005 using IPTV over DVB-T technology while lone satellite programming provider ASTRO has been transmitting in DVB-S since it's inception in 1996.

With the exception of Sky PerfecTV!, Japan uses different formats in all areas (ISDB), which are however quite similar to their DVB counterparts. SkyPerfect is a satellite provider using DVB on their 124 and 128 degrees east satellites. Their satellite at 110 degrees east does not use DVB, however.

In North America, DVB-S is often used in signal compression and encoding of digital satellite communications alongside Hughes DSS. Unlike Motorola's DigiCipher 2 standard, DVB has a wider adoption in terms of the number of manufacturers of receivers. Cable operators either use DVB-C or OpenCable. Terrestrial HDTV broadcasts use ATSC digital encoding with 8VSB modulation instead of DVB-T's COFDM.

In Hong Kong, several cable TV operators such as TVB Pay Vision and Cable TV have already started using DVB-C. The government has decided digital terrestrial broadcasting will start not later than 2007, and it is up to the broadcasters to decide which system to use. If mainland China still not decide which system to use by mid-2006, it is very likely that DVB-T will be adopted.

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 the last year.

World maps

External links

Digital television | High-definition television | Open standards

DVB | Digitální televizní vysílání | Digital Video Broadcasting | DVB | Digital Video Broadcasting | DVB | DVB | Digital Video Broadcast | DVB | Digital Video Broadcasting | DVB | DVB | Digital Video Broadcasting | DVB | DVB

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