Digital television

as digital television one designates the radiant emittance form digitized of television programs in.

The production and processing of the picture and sound signals happen since years (conditions 04/06) in digital form. The spreading of the picture and clay/tone data happens today (conditions 05/06) usuallyin digital form (DVB-T, DVB-C, DVB-S, IPTV). New television sets know the digital signals (DVB) directly received (see digital televisions). For old, similar television sets the digital data stream with appropriate devices must (Digital Receiver, setting OI boxes) again (see also decoders) become reconverted into similar signals. The spreading of the picture and sound signals partly today still happens in similar way (conditions 05/06). However the old similar television goes to the end against (see in addition to similar one “SWITCH off”).

  • Analog technique is the direct information transfer by signal level change (or “- variance” ) ()
  • digital technique is the indirect information transfer by interpretation of signal level changes (out/in)


table of contents

standards and spreading ways

most digital transmission standards working with data compression, i.e. that the data sets of the digital origin signals everafter claims of quality before the spreading to be reduced, in order to save range (by decrease of the bit rate). Today the generally used data reduction system is called MPEG and exists both for audio and video signals; The different MPEG-based codes leave themselves for data storage as well as to the data communicationuse. Also the popular MP3 - format or the usual DVD standards is based on MPEG. Depending upon transmission platform one differentiates the following technical variants with the digital television (DVB): DVB-S (satellite), DVB-T (terrestrial antenna receipt), DVB-C (cable), DVB-H (Handy TV); all four are based (at present)on the MPEG-2 standard.

By the digital transmission technology numerous auxiliary services with the existing television programs can be combined: E.G. Data services with additional information and illustrations in the Design of web pages; extended teletex seaweed messenger; Transmitter identifications, those rapid finding e.g. in the automatic browsing of digital Receivermake possible; and not least digital program magazines and information to the program sequence (EPG). By the mechanism of a backward channel (in the cable or via satellite) these services can be made interactive - that is, one can associate with the offerer,Enamels dispatch or as users to be registered. Triple Play one calls the parallel spreading of broadcast, telephone and Internet over the same transmission path (e.g. Cable).

Digital transmission methods are favourable because of their high compatibility to computer systems (receipt, storage, treatment, transformation or further spread further)and up-to-date; by the small spreading costs over satellite or cable (a digital television program needs only one fifth to a tenth of the range of a similar channel) also smaller offerers can spread their programs supraregional. In addition large television companies know their existing offereconomically by numerous auxiliary channels extend. A large advantage exists also in the Kompatiblität of digital television with digital sound broadcasting (DAB)

world-wide the digital satellite-to-receiver telecasting (DVB-S) the similar spreading (from cost reasons) already completely replaced. Only inOne holds Germany because of the strong position of the public television (provisional) at uneconomic analog technique. Until 2010 is to be adjusted however both terrestrial as well as in the satellite and wiring loom realm all similar signals in favor of digital technology (see in addition to similar one “SWITCH off”).

In Berlin already terrestrial digital television ( DVB-T) is mandatory since 2003 - only the transmitters from Brandenburg can be received in Berlin still similarly. In other areas of Germany, where DVB-T was already introduced, the transmitting power of the remaining becomessimilar to sending public programs strongly driven down, in order to increase the conversion pressure to the population. Today accomplished from cost reasons nearly only harder transferred (disconnection of the similar signals during engagement of the digital signals). Here a DVB-T - example of east Westphalia<ref>Conversion of similar broadcast to digital broadcast by the example east Westphalia of DVB-T. At a deadline the similar broadcast is stopped and the digital broadcast up-peeled. In addition the old similar transmitting plant becomes by a new by helicopters within fewer hoursdigital transmitting plant replaces. From the comments on this article it follows that some concerning were surprised by the conversion. The local press had hardly dedicated itself to the topic.</ref>, for Bavaria <ref> Change-over of the similar broadcast on digital broadcast toExample DVB-T in Bavaria: “Transmitters such as pro filters, Sat.1 or RTL caps with that 30. May the similar transmission via antenna in completely Bavaria. “ </ref>, for Baden-Wuerttemberg and Rhineland-Palatinate <ref> “in May” 2006 become “in the regions Stuttgart, Mannheim, Ludwigshafen, Heidelberg,the Vorderpfalz and Kaiserslautern (...) the similar-terrestrial antenna television (...) changed over to digital quality (DVB-T). (...) In Heidelberg, Mannheim, Ludwigshafen and the Vorderpfalz finds the so-called “hard presumably transferred” to 17. To May instead of, then the two transmitters king chair and be wine-offerednur noch digitale Programmsignale verbreiten。 (...) Gradual will after “transferred in the starting islands” the further development of DVB-T in Baden-Wuerttemberg and Rhineland-Palatinate to follow. To at the end of of 2008 is transferred after the conceptions of SWR and Second Channel of German Television to be country-wide final. “ </ref>, for Hessen <ref> HR-online.de: “Starting signal for DVB-T in completely Hessen to 29. May 2006. (...) the similar radiant emittance over antenna becomes to 29. May 2006 adjusted in Hessen " (harder transferred).</ref>. Country widely is transferred to end of 2008 carried outits (see also conversion to DVB-T).

Digital data streams leave themselves also in computer-based nets, e.g. in the Internet spread and with appropriate software on the screen represent or on data media note (z. B. IPTV). Digital signals (English also Streams) can mentioned be transferred into different standards, which are among themselves only limited compatible related however. Most receivers can be updated however by means of an UPDATE function over satellite, Internet or cable or extended by other transmission codes. There nowadays manyPrograms coded send, need one for the receipt of the offer a so-called receipt module, usually in form of a plug-in card, which is slid into the Receiver. Because of the large variety at coding systems many modern devices have several map pits (“card locations”), around thoseTo be able to receive services of different offerers.

One calls these platform-spreading devices CICAM Receiver = Common interface Conditional ACCESS of modules. Contrary to that end of the 90's of the Kirch company for its Pay TV offer at that time premiere promoteten D-box, only toDecoding was suitable by premiere and other Pay TV offerers discriminated against, contained CICAM Receiver interfaces for all usual coding technologies (Betacrypt, Nagravision, Videoguard, Viaccess, Cryptoworks among other things).

The registration, actualization and customer administration takes place then usually on-line (and/or. via satellite). Thus leave themselves for example of“Cracked” coding codes to hackers by others replace or exclude delinquent customers from the receipt. The offered devices have depending upon platform different technologies, why Digitalreceiver for the satellite reception cannot be used for digital cable receipt or in reverse.

historyand current development

the digital television was offered to DirecTV in the USA over commercially for the first time in the spring 1994 by satellite under the label name.

Twelve European countries agreed end of 1993 on it, as rapidly as possible a specification for the transmission of digital television signals overTo provide satellite and cable; the introduction was already planned for 1995. From it adult the DVB became in Germany to 28 then for the first time. July 1996 of the Pay TV organizer DF1 (digital television 1), created newly for it, radiated. Because of Erfolglosigkeit despitelarge-scale Werbekampagne and popular sport events it was folded up later with the paying transmitter premiere from the same house, the Kirch group. The meanwhile quoted transmitter could develop its capacity owing to the digital transmission technology fully and many supplementary product lines and/or. Topic channels (also ofForeign offerers) to its offer take up.

Meanwhile almost all supraregional German transmitters, privately as publicly, began predominantly over the Astra - satellites of the operator SES parallel to the similar with the digital radiant emittance. Beside additional, only transmitters accessible for digital users use above allmany new section programs as well as some Lokalsender economical digital technique. Some smaller television companies send the television signal via DSL or glass fiber net by the Internet, where it is taken up from the operators of a Uplink station (usually larger television stations) and overacted on the satellites. Soe.g. become high transmission costs, like them. with the expensive point-to-point radio telecommunication would develop, avoided. In this way the spatial distance between program offerers and transmitters is problem-free overcome.

By the surface covering development of the Internets and the introduction of ADSL2 as new transmission standard can digital television in the future also directly from the Internet to be received. By the high Downloadraten with ADSL2 or light conductor the receipt quality and disturbance resistance of the programs are just as high as e.g. over the classical cable or satellite. Gradually those becameVision of the “world-wide television” over, for the time being along wide-band data networks, reality.

At the beginning of of 2003 began somewhat later than in comparable countries (GB: 1996) the introduction of DVB-T, the terrestrial DVB variant, in the region Berlin, but with the completeDisconnection of the similar terrestrial television in this area already in August everything of the same yearly took Germany world-wide a role of the pioneer. To Berlin first the conversion to DVB-T followed in further densely populated areas. Starting from 2004 becomes in Europe over satellite in HDTV- Standard radiated.

Meanwhile violently the validity of digital “basic charges” for advertising-financed television programs such as RTL or Sat1 one discusses, which want to introduce the television operators medium-term both in the cable as well as over satellite. To the present concentration tendencies on the digital television seealso project Dolphin

an opposite development suggests itself in other countries: Thus give up in Great Britain ever more programs their coding. During the 90's most British television programs on the platform of British Sky Broadcasting (BSkyB) would send, thatbeside own programs also stranger of offers marketed and with a basic coding provided. Many this offerer, among them also BBC and ITV, separated from Sky and send meanwhile unkodiert.

At present more than 120 television programs intended for the British market are unencryptedto receive over satellite, among them many commercial full and section programs. They become under the labels Free ton air (FTA, name for all unencrypted offers), Freesat (mark-protected name for program complexes of BBC and ITV) and/or. Freeview (terrestrial DVB T receipt with approx. 30Programs) markets. Around the competition to withstand even the Pay TV company BSkyB took its own unencrypted, advertising-financed program in enterprise.

The coded offer of BSkyB (Sky digital) is the most extensive of Europe and offers a multiplicity of film, sport and maintenance channelsas well as numerous section channels also of foreign offerers such as Disney, Discovery, NBC universal or Viacom. BSkyB belongs to the Imperium of the Medientycoons Rupert Murdoch (news corporation).

In many European countries coded Kabelbouquets was established, those usually completely into the cable fedbecome. Many transmitters code for license-legal reasons, because they acquired only radiant emittance rights for a limited transmission area. The receipt of these programs is however free, decoding maps (“Smartcards”) to the spectators is usually free of charge dispatched.

In the Netherlands all full programs code itSignal over satellite, because all international productions, with exception of some child transmissions, are radiated in the source language (with sub-titles). Film and sport offers become in the Canal Digitaal - Bouquet (cable, satellite) markets. The large cable companies offer digital packages, those beside Canal Digitaal also thoseinternational television marks such as Discovery and MTV contain. Also they are provided with Netherlands sub-titles.

The situation is similar in Scandinavia and most countries of Eastern Europe, where the expenditure connected with the synchronisation would be economically unprofitable (exceptions: Russia, partial Poland). Overlicense-legal problems out of the way to go, all programs are usually coded. The strong position of the subscription television in these countries explains itself also by the small advertising market.

In Belgium, in particular in Flanders, the digital program offer concentrates nearly completelyon the cable and/or. ADSL. There is hardly satellite direct receipt. Also in Switzerland liable to pay the costs digital packages become (v.a. Teleclub) in the cable offered. In Austria the satellite reception has a strong position; similarly as in Germany the subscription range is allotted almost exclusively to PREMIERE,that applies also to the cable receipt.

In France three large Pay TV networks, Canal Satellite numerique ( better admits than Canal+ ) dominate, OFF sow and TPS (Télévision par satellite). All three cooperate again with numerous foreign offerers, among other things with thatlarge national television stations. In France only few programs are freely receiptable.

Over Eutelsat Sky Italia, the dominating digital television company of Italy sends. As BSkyB it is controlled by Rupert Murdoch. Sky Italia went out of the fusion of the two former competitorsSTREAM and TELE+ out.

In Spain the two digital platforms Vía digital from Telefónica and Canal Satélite digital from Sogecable fused to the monopolist digital +. The union was owed a uniform program and structural policy and better earning facilities. In the cable dominatethe market leaders AUNA and ONO. Although in Spain almost all international productions with Spanish synchronisation are radiated, most national television channels code their program over satellite. Lately however an intensified trend is to be registered for unencrypted radiant emittance; forwardsall regional networks and many section transmitters go this way. Former Pay TV channels turn into increasingly for advertising-financed radiant emittance.

“Basic charges” for advertising-financed television offers give it usually only in the cable. Some smaller program offerers however still prefer a mixing financing, upAdvertisement and a low subscription fee are based. This basic subscription is divided however on a large number of section transmitters, which are driven out together in so-called “basis packages”. This mixing financing is usually, if a program cannot be operated by incomes from advertising alone economically, aboutbecause the transmission area or the target group is too small.

television over Internet

with the IPTV - procedures (internet minutes TV) are world-wide spread already today numerous television programs using Internet minutes. At present become over 200 topic channels inGerman language offered, which will receive over each Webable terminal with sufficient arithmetic performance can. In addition among other things information channels of larger enterprises belong such as mark manufacturers or travel agencies; meanwhile however many journalistically high-quality section channels are also already offered for most different ranges of topics. Still are the programs exclusively for the Internet receipt conceived, it can be merged however in the near future also problem-free in Kabelbouqets or on other way spread further. So that can be used Internet in the future also as pure transmission path, dressing and receipt of the serviceswould lie then at the cable companies.IPTV is not conceived yet for the mass receipt, can be made measure suited already however by armament with multicast - capable servers in few years. Lately a quasi-monopoly has itself approximately around the resident of Munich media entrepreneur Ingo wolf establishes, which offers or spreads numerous section programs further supported by the IPTV technology usually unencrypted. In the future that would be allowed to do Internet for all television companies to hard contested terrain to become, RTL and SAT1/Pro7 become their programs also in the Internet to spread already shortly.See also IPTV.

technology

the transmission takes place in Europe as in most states the world in the DVB - standard, that beside television and radio programs also additional information (e.g. Sub-title, EPG) and new data services (e.g. Texts, PC data, MHP) offers. There are different transfer options for DVB:

Japan uses a related procedure (ISDB), while the USA at least for the antenna receipt its ATSC - format publicise.

ThoseRange of a typical transponder (satellite channel) on the well-known broadcasting satellite Astra amounts to usually 33 MHz, corresponds to a net date rate of 36 Mbit/seconds and/or. a symbol rate of 26 Msymb/s. A television station needs usually about 3-4 Mbit/seconds, depending upon its symbol rate (coding ofever 2 bits to a “symbol”). It moves between 2,2 and 2,75 Msymb/s. Together with the error correction (usually 3/4 using to correction data) the necessary data rate results. The faster the picture changes (changes in the screen layout), is the higherthe necessary data rate. Sport and Actionszenen require thus more range than movement-poor sequences (Talkshows etc.). If the range is too narrowly computed, it comes with fast scene change when high resolution to artifacts (Bauklötzchen effects).

Usually also still radio broadcasting programs become over a transponder(per 64-320/second kbit; CD quality: 192kbit/sec) and various data services transfer. Over a pure television transponder comfortably eight television programs can be transferred in good quality, however only a similar! By the introduction of the more efficient MPEG-4 codec can be compressed in the future still more effectively,continuous picture and clay/tone quality can in the future more than 10 television programs for each transponder be transferred. By time-consuming coding and decoding of the television signal it comes in relation to the similar radiant emittance to mehrsekündigen delays (, is the more complicated the coding algorithm is the more efficiently compressed).

With DVB only the Fersehprogramm in MPEG-2 is coded, “interlocked” afterwards the program with possible auxiliary services in the multiplexer. Several programs (television, radio etc.) within a package can be combined in such a way to a data stream, which also transportation stream is called. Subsequently,if the data stream with the carrier signal is modulated, strengthens and to the transmitter/satellite and/or. to the cable head station guided.


comparative table analog technique/digital television

similar to digital
rushes (S/N can amount to 256/1 and is not perceptible thereby any longer) to noise leads because of Fehlerkorrkturto few however misfires strong for it
compression of the picture with PAL compression with MPEG-2
Interlacing intermediate frames
colors with low horizontal range colors with low horizontal and vertical range transfer transferred (like video home system)
transmitters frequency bands assigned transmitters becomeFrequency bands and therein dynamically time packages assigned
arithmetic performance the picture parameters (number of lines, column number, frequency, compression factor) are hard wire the picture parameters are limited by the DSP. The compression factor is dynamic.
Clay/tone becomes frequency-modulated. This needs less transmitting power however more range clay/tone is indigital data stream contain.
Videotex needs to contain its own Dekoder videotex is in the digital data stream.
PAL uses quadrature amplitudes modulation (QAM) DVB-T uses quadrature amplitudes modulation
of firm range and S/N range and S/N can be exchanged against each other. To the decrease of the transmitting powerS/N is selected usually more badly and a Equalizer in the receiver permits small gaps in the UHF television volume, thus more range for each transmitter.

see also

sources

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