Digital Video Broadcasting
From Wikipedia, the free encyclopedia
| List of digital video broadcast standards |
| DVB Family (Europe) |
| DVB-S (Satellite) |
| DVB-T (Terrestrial) |
| DVB-C (Cable) |
| DVB-H (Mobile) |
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| ATSC Family (USA) |
| ATSC (Terrestrial) |
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| ISDB Family (Japan) |
| ISDB-S (Satellite) |
| ISDB-T (Terrestrial) |
| ISDB-C (Cable) |
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| DMB Family (China) |
| DMB-T |
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| Codecs |
| MPEG-2 |
| MPEG-4 |
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| Frequency bands |
| VHF |
| UHF |
| SHF |
Digital Video Broadcasting (DVB) is a suite of internationally accepted open standards for digital television. DVB standards are maintained by the DVB Project, an 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 Union (EBU). The interaction of the DVB sub-standards is described in the DVB Cookbook (DVB-Cook).
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[edit] 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); terrestrial television (DVB-T, DVB-T2) and digital terrestrial television for handhelds (DVB-H); 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-2 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 standard will be published after march 2008 and is expected to be approved and submitted to ETSI during 2008.
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 SFN (as in Germany, Sweden...).
[edit] 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.
[edit] 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 and it's said that CPCM is the DVB's answer to the failed American Broadcast Flag.[1]
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 solution 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).
[edit] 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.
List of other user interaction software platforms.
[edit] 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
[edit] 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 (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.
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, Mexico and South Korea) chose ATSC instead of DVB-T.
[edit] Hong Kong
In Hong Kong, 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 31st Dec 2007.[2]
[edit] Japan
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.
[edit] Malaysia
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 its inception in 1996. Free-to-air DVB-T trials began in late 2006 with a simulcast of both RTM1 and RTM2 plus a new channel called RTM3/RTMi. In April 2007, RTM announced that the outcome of the test is favorable and expects DVB-T to go public by the end of 2007. 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. Analog shut-off date is also announced to be sometime in 2015.
[edit] Norway
In Norway, DVB broadcasting is marketed under RiksTV (encrypted pay channels) & NRK (unecrypted public channels), DVB-T via (terrestrial) began in November 2007 Norway is one case that is different from other countries, as it uses H.264 with LATM/ADTS HE-AAC audio encoding Notably most DVB software for PC don't work with this, only in late 2007 software like DVBViewer with libfaad2 Wrapper supported this, same goes for STBs and HDTVs, they must support H.264 and HE-AAC, Sony Released Bravia W3000, X3000, X3500 that supports Norway's DVB-T implementation, and Sagem ITD91 HD, Grundig DTR 8720 STBs
[edit] New Zealand
In New Zealand, DVB broadcasting is marketed under the Freeview brand name. DVB-S broadcasts via satellite began on 2 May 2007 and DVB-T (terrestrial) broadcasts are scheduled to begin April 1st 2008. Initially, consumers will be required to purchase set-top boxes, as DVB-capable TV sets are not yet available in New Zealand.
[edit] 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.
[edit] 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.
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[edit] See also
- ATSC Standards - Advanced Television Systems Committee Standard
- CI+ Common Interface Plus
- DVB-C (Digital Video Broadcasting - Cable)
- Digital terrestrial television (DTT or DTTV)
- Digital audio broadcasting (DAB)
- Digital Radio Mondiale (DRM)
- Digital Multimedia Broadcasting (DMB)
- DVB-CPCM - Content Protection and Content Management
- DMB-T - Digital Multimedia Broadcast-Terrestrial
- ETSI Satellite Digital Radio (SDR)
- FTA Receiver
- ISDB - Integrated Services Digital Broadcasting
- IPTV
- List of digital television deployments by country
[edit] References
- ^ Europe's Broadcast Flag. Electronic Frontier Foundation (September 29, 2005). Retrieved on 2007-08-15.
- ^ http://www.digitaltv.gov.hk/general/news_26112007.htm Hong Kong is entering a new era of digital broadcasting
[edit] External links
- DVB Project
- DVB Fact Sheets including an introduction to the DVB Project
- Official DVB-H Information
- DVB Services Sarl, MHP PKI Root Certificate Authority
- DVB-T broadcasting with Linux
- DVB Worldwide
- Information on DVB-CPCM from the DVB Project including a Fact Sheet and FAQ
- DVB Adoption Map, DVB.org
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