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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 300 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 (http://www.etsi.org/services_products/freestandard/home.htm) after registration.
How the several DVB sub-standards interact is described in the DVB Cookbook (DVB-Cook).
Transmission
The core standards of DVB are DVB-S (satellite television and satellite internet), DVB-C (cable) and DVB-T (terrestrial), which are all based upon MPEG-2 (DVB-MPEG) for audio and video coding as well as the transport stream and are capable of high definition television (HDTV) as well. Upcoming is DVB-H for mobile reception in cellular phone frequency bands.
These flavors differ mainly in the modulations used, due to the requirements of different frequency bands. The high frequency DVB-S uses QPSK, lower hertz DVB-C uses QAM (64-QAM in general) and DVB-T (in VHF and/or UHF band) uses COFDM.
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. Germany aims to be fully covered with digital television in 2010. Italy will completely convert its terrestrial analog broadcasts to DVB-T by 2006. In Australia, terrestrial analog broadcasts are to cease in 2008 after DVB-T takeover. In Spain, analog switch-off is due at the beginning of 2010.
Interaction
Besides audio and video transmission, DVB also defines data connections (DVB-DATA) with return channels DVB-RC* for several media (DECT, GSM, PSTN/ISDN etc.) and protocolos (DVB-IPI: Internet Protocol, DVB-NPI: network protocol independent). This is for example used for interactive interfaces like Multimedia Home Platform (DVB-MHP) and Electronic Program Guides (EPG).
Legacy technologies like teletext (DVB-TXT) and VBI (DVB-VBI) are also supported to ease conversion. However for many applications more advanced alternatives like DVB-SUB for sub-titling are available. The features are described with Service Information (DVB-SI).
Interfaces and Encryption
DVB describes a lot of (network) interfaces, but most importantly the Common Interface (DVB-CI) for Conditional Access (DVB-CA) with the Common Scrambling Algorithm (DVB-CSA) required for (de-)scrambling pay TV.
Adoption
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 and a few (Argentina and South Korea) chose ATSC instead of DVB-T for now.
With the exception of SkyPerfect, 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.
As of 2004, DVB-T television sets are still significantly more expensive than analog television sets. This is creating serious consternation among consumers in countries such as Australia that have mandated to switch off analog television in a few years. But the high price of digital television sets is expected to diminish shortly.
World maps
- DVB-S (http://www.dvb.org/graphics/internal/Adoption-Map_DVB-S_April_20.jpg),
- DVB-C (http://www.dvb.org/graphics/internal/Adoption-Map_DVB-C_April_20.jpg),
- DVB-T (http://www.dvb.org/graphics/internal/Adoption-Map_DVB-T.jpg),
- MHP (http://www.mhp.org/graphics/mhp-sitewide/Adoption-Map_mhp.jpg).
See also
External links
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