The Full Wiki

More info on Digital Video Broadcasting

Digital Video Broadcasting: Map

Advertisements
  
  

Wikipedia article:

Map showing all locations mentioned on Wikipedia article:



Official DVB logo, found on compliant devices


Digital Video Broadcasting (DVB) is a suite of internationally accepted open standards for digital television. DVB standards are maintained by the DVB Project, an international industry consortium with more than 270 members, and they are published by a Joint Technical Committee (JTC) of European Telecommunications Standards Institute (ETSI), European Committee for Electrotechnical Standardization (CENELEC) and European Broadcasting Unionmarker (EBU). The interaction of the DVB sub-standards is described in the DVB Cookbook. Many aspects of DVB are patented, including elements of the MPEG video coding and audio coding.

Transmission

DVB systems distribute data using a variety of approaches, including by satellite (DVB-S, DVB-S2 and DVB-SH; also DVB-SMATV for distribution via SMATV); cable (DVB-C, DVB-C2); terrestrial television (DVB-T, DVB-T2) and digital terrestrial television for handhelds (DVB-H,DVB-SH); and via microwave using DTT (DVB-MT), the MMDS (DVB-MC), and/or MVDS standards (DVB-MS).

These standards define the physical layer and data link layer of the 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 transport streams with some additional constraints (DVB-MPEG). A standard for temporally-compressed distribution to mobile devices (DVB-H) was published in November 2004.

These distribution systems differ mainly in the modulation schemes used and error correcting codes used, due to the different technical constraints. DVB-S (SHF) uses QPSK, 8PSK or 16-QAM. 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: 16-QAM, 32-QAM, 64-QAM, 128-QAM or 256-QAM. Lastly, DVB-T (VHF/UHF) uses 16-QAM or 64-QAM (or QPSK) in combination with COFDM and can support hierarchical modulation.

The DVB-T2 specification was approved by the DVB Steering Board in June 2008 and sent to ETSI for adoption as a formal standard. ETSI is expected to publish the standard in July 2009.

The DVB-T2 standard will give more-robust TV reception and increase the possible bit-rate by over 30% for single transmitters (as in the UK) and is expected to increase the max bit-rate by over 50% in large single-frequency networks (as in Germany, Sweden).

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-IPTV: Internet Protocol; DVB-NPI: network protocol independent).

Older technologies such as 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 physical Common Interface (DVB-CI) for accessing scrambled content. DVB-CA providers develop their wholly proprietary conditional access systems with reference to these specifications. Multiple simultaneous CA systems can be assigned to a scrambled DVB program stream providing operational and commercial flexibility for the service provider.

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. DVB-CPCM has been the source of much controversy in the popular press andIt is said that CPCM is the DVB's answer to the failed American Broadcast Flag.

DVB transports include metadata called Service Information (DVB-SI, ETSI EN 300 468, ETSI TR 101 211) that links the various elementary streams into coherent programs and provides human-readable descriptions for electronic program guides as well as for automatic searching and filtering.

Recently, DVB has adopted a profile of the metadata defined by the TV-Anytime Forum (DVB-TVA, ETSI TS 102323). This is an XML Schema based technology and the DVB profile is tailored for enhanced Personal Digital Recorders. DVB lately also started an activity to develop a service for IPTV (DVB-IPI, ETSI TR 102033, ETSI TS 102034, ETSI TS 102814) which also includes metadata definitions for a broadband content guide (DVB-BCG, ETSI TS 102 539).

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 Kingdommarker's Digital TV Group in late 1998. In 2003 Berlinmarker, Germanymarker 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 Indiamarker 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 Koreamarker) chose ATSC instead of DVB-T.

Denmark

In Denmarkmarker, DVB-T replaced the analog transmission system for TV on November 1st 2009. Danish national digital TV transmission has been outsourced to the company Boxer TV A/S ( Boxer TV), acting as gatekeeper organization for terrestrial TV transmission in Denmark.

Hong Kong

In Hong Kongmarker, several cable TV operators such as TVB Pay Vision and Cable TV have already started using DVB-S or DVB-C. The government however has adopted the DMB-T/H standard, developed in mainland China, for its digital terrestrial broadcasting services which has started since 31 December 2007.

Israel

DVB-T broadcasts using H.264 will commence in Israel in July 2009. Analog broadcasts will be turned off 18 months after the start of DVB-T transmission.On 01 June 2009 the broadcast trial started and the launch will be on 01 August 2009.

Japan

With the exception of Sky PerfecTV!, Japanmarker 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.

Malaysia

In Malaysiamarker, a new Pay-TV station MiTV began service in September 2005 using DVB-IPTV technology while lone satellite programming provider ASTRO has been transmitting in DVB-S since its inception in 1996. Free-to-air DVB-T trials began in late 2006 with a simulcast of both TV1 and TV2 plus a new channel called RTM3/RTMi. In April 2007, RTM announced that the outcome of the test is favourable and expects DVB-T to go public by the end of 2007. However, the system did not go public as planned. As of 2008, the trial digital line-up has expanded to include a Music Television channel called Muzik Aktif, and a Sports channel called Arena, with a news channel called Berita Aktif planned for inclusion in the extended trials soon. Also, High Definition trials were performed during the Beijing Olympics and the outcome was also favourable. It has been announced that the system will go public sometime in 2009.

As of 2009, MiTV has closed down, changed its name to U-Television, and announced that they are changing to use scrambled DVB-T upon relaunch instead of the DVB-IPTV system used prior to shutting down.

Analogue shut-off date is also announced to be sometime in 2015.

Norway

In Norwaymarker, DVB broadcasting is marketed under RiksTV (encrypted pay channels) and NRKmarker (unecrypted public channels). DVB-T broadcasting via the terrestrial network began in November 2007, and has subsequently been rolled out one part of the country at a time.The Norwegian implementation of DVB-T is different from most others, as it uses H.264 with HE-AAC audio encoding, while most other countries have adapted the less recent MPEG-2 standard. Notably most DVB software for PC have problems with this, though in late 2007 software compatible software has been released, like DVBViewer using the libfaad2 library. Sony has released several HDTVs (Bravia W3000, X3000, X3500, E4000, V4500, W4000, W4500, X4500) that support Norway's DVB-T implementation without use of a separate set-top box, and Sagem ITD91 HD, Grundig DTR 8720 STBs are others.

New Zealand

In New Zealandmarker, DVB broadcasting is marketed under the Freeview brand name. SD MPEG-2 DVB-S broadcasts via satellite began on 2 May 2007 and DVB-T (terrestrial) broadcasts began April 2008 broadcasting in HD H.264 video with HE-AAC audio.

North America

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.

Canada, Mexico, El Salvador, Honduras and the United States have chosen ATSC instead of DVB-T.

Portugal

Portugal follows the DVB-T implementation, using H.264 with MPEG4 audio encoding. It is live since April 29, 2009 and the switch-off date for all analogic signals is April 26, 2012.

Taiwan

In Taiwanmarker, cable television is broadcasted using DVB-C. The government also adopted DVB-T for its digital terrestrial broadcasting services.

DVB compliant products

Companies that manufacture a product which is compliant to one or more DVB standards have the option of registering a Declaration of Conformity for that product. Wherever the DVB trademark is used in relation to a product – be it a broadcast, a service, an application or equipment – the product must be registered with the DVB Project Office.

See also



References

  1. Press release from The Danish Radio and Television Board
  2. Announcement from The Danish Ministry of Culture (in Danish)
  3. Hong Kong is entering a new era of digital broadcasting


External links




Embed code:
Advertisements






Got something to say? Make a comment.
Your name
Your email address
Message