DVB

Ti Wikipédia, énsiklopédia bébas
Luncat ka: pituduh, sungsi

DVB, singgetan tina Digital Video Broadcasting, nyaeta hiji suite standar bébas nu ditarima sacara internasional keur televisi digital. Standar DVB diropea ku DVB Project, hiji konsorsium industri nu anggotana leuwih ti 270, tur dipublikasikeun ku hiji Joint Technical Committee (JTC) antara European Telecommunications Standards Institute (ETSI), European Committee for Electrotechnical Standardization (CENELEC) jeung European Broadcasting Union (EBU). Interaksi sub-standar DVB dijentrekeun dina DVB Cookbook (DVB-Cook).

Transmisi[édit | sunting sumber]

Sistim DVB nyebarkeun data make sababaraha cara, kaasup ngaliwatan satelit (DVB-S, DVB-S2 katut DVB-SH; oge DVB-SMATV keur distribusi ngaliwatan SMATV); kabel (DVB-C); televisi téréstrial (DVB-T) jeung televisi téréstrial digital keur handheld (DVB-H); sarta ngaliwatan gelombang mikro make DTT (DVB-MT), MMDS (DVB-MC), jeung/atawa standar MVDS (DVB-MS)

Panneau travaux.png Artikel ieu keur dikeureuyeuh, ditarjamahkeun tina basa Inggris.
Bantosanna diantos kanggo narjamahkeun.

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, 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 hierarchical modulation

Eusi[édit | sunting sumber]

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.

Enkripsi jeung metadata[édit | sunting sumber]

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 publication expected December 2006).

Software platform[édit | sunting sumber]

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.

Saluran keur balik deui (return channel)[édit | sunting sumber]

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

Adopsi[édit | sunting sumber]

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.

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.

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

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-S or 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. Originally it was thought that mainland China would adopt DVB-T, but instead they have decided to create their own digital television standard, the DMB-T/H standard, made in collaboration of two Chinese universities.

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.

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 in early 2008. Initially, consumers will be required to purchase set-top boxes, as DVB-capable TV sets are not yet available in New Zealand.

Produk nu cocog jeung DVB[édit | sunting sumber]

Companies that manufacture a product that 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.

Citakan:Wireless video

Tempo oge[édit | sunting sumber]

Rujukan[édit | sunting sumber]

  1. "Europe's Broadcast Flag". Electronic Frontier Foundation. 29 Séptémber 2005. Diarsipkan dari yang asli pada 13 Oktober 2005. Diakses pada 15 Agustus 2007. 

Tumbu luar[édit | sunting sumber]