As digital television is referred to the broadcasting of television programs in digitized form. For this purpose, the conventional (analog) picture and sound signals are converted into digital data streams (binary codes) with the help of so-called A / D converters.
The production and processing of the image and sound signals has been done in digital form for years (as of April 2006). Today (as of 05/06) the distribution of image and sound data is mostly in digital form ( DVB-T , DVB-C , DVB-IPI , DVB-S , DVB-H , DMB , IPTV ). New television sets can process the digital signals ( DVB ) directly ( see IDTV ). For old, analog television sets, the digital data stream must be converted into analog signals using the appropriate devices ( digital receivers , set-top boxes ). In some cases, the image and sound signals are still distributed in an analog way today (as of 2015/12). However, analog television is coming to an end ( see analog switch-off ).
Norms and distribution channels
Most digital transmission standards work with data reduction, i. This means that the data volumes of the digital original signals have to be reduced with a loss of image quality prior to distribution in order to save the data rate (by reducing the bit rate). The data reduction system commonly used today is called MPEG and exists for both audio and video signals. The various MPEG-based codes can be used for data storage and data transmission. When developing the reduction process, the focus is on preserving the image quality as much as possible at given bit rates. The popular MP3 format or the common DVD standards are also based on MPEG. Depending on the transmission platform, a distinction is made between the following technical variants of digital television ( DVB ): DVB-S (satellite), DVB-T (terrestrial antenna reception ), DVB- C (cable), DVB-H ( mobile television ), DVB-IPTV ( IPTV) ); all are based (currently) on the MPEG-2 standard.
Thanks to the digital broadcast technology, numerous additional services can be combined with the existing television programs: B. Data services with additional information and illustrations in the design of websites; extended teletext offers; Transmitter IDs that make it easy to find z. B. enable digital receivers in automatic search; and last but not least, digital program guides and information on the program schedule ( EPG ). By setting up a return channel (in cable or via satellite), these services can be made interactive - that is, you can contact the provider, send e-mails or be registered as a user. As a triple play is called the parallel transmission of programs, telephone and internet on the same transmission path (z. B. cable).
Digital transmission methods are advantageous and up-to-date because of their high compatibility with computer systems (reception, storage, processing, conversion or further distribution); Due to the low distribution costs via satellite or cable (five to ten digital television programs require roughly the same transmission capacity as an analogue program), smaller providers can also broadcast their programs nationwide. In addition, large television groups can inexpensively expand their existing offering with numerous additional channels. Another great advantage is the compatibility of radio and television standards with DVB-T, so that a television station in the data stream of a station package can be exchanged for a corresponding number of radio stations or vice versa , so that the operators of the stations can better respond to the needs of the program providers .
Terrestrial digital television ( DVB-T ) has been compulsory in Berlin since 2003 . Due to the shortage of channels, a hard switchover (switching off the analog signals when switching on the digital signals) is almost always carried out. The changeover was completed nationwide at the end of 2008.
Digital data streams can also be used in computer-based networks, e.g. B. disseminated on the Internet and displayed with the appropriate software on the screen or recorded on data storage media (e.g. IPTV ). Digital signals (English streams ) can be transmitted in different standards, which are related but only compatible with one another to a limited extent. Most receiving devices can, however, be updated by means of an update function via satellite, Internet or cable, or other transmission codes can be added. Since many programs send encrypted nowadays, a so-called receiver module is required to receive the offer , usually in the form of a plug-in card that is inserted into the receiver. Because of the large variety of encryption systems, many modern devices have several card slots ( slots ) in order to be able to receive the services of various providers.
These cross-platform devices are called CICAM receivers = Common Interface Conditional Access Module . In contrast to the late 1990s by the Kirch Group onetime for its pay-TV service Premiere were promoting the d-box , which was only suitable for decrypting Premiere and other pay-TV providers discriminated containing CICAM receiver interfaces for all common encryption technologies (Betacrypt, Nagravision, Videoguard, Viaccess, Cryptoworks and others).
Registration, updating and customer management are usually done online (or via satellite). For example, encryption codes cracked by hackers can be replaced by others or customers who are in default can be excluded from reception. The devices offered have different technologies depending on the platform, which is why digital receivers for satellite reception cannot be used for digital cable reception or vice versa.
History and current development
Development towards digital television
At the end of 1993, twelve European countries agreed to draw up a specification for the transmission of digital television signals via satellite and cable as quickly as possible; the introduction was planned for 1995. The resulting DVB was then broadcast in Germany for the first time on July 28, 1996 by the newly created pay-TV operator DF1 ( digital television 1 ). Due to its unsuccessfulness despite a large-scale advertising campaign and popular sporting events, it was later merged with the pay-TV channel Premiere from the same company, the Kirch Group . The broadcaster, which has meanwhile been listed on the stock exchange, was able to significantly expand its capacity thanks to the digital transmission technology and to include many additional programs and themed channels (also from third-party providers) in its offer.
In the meantime, almost all national German television stations began broadcasting their programs digitally, primarily via the Astra satellites operated by the operator SES, parallel to the analogue ones. In addition to additional channels that are only accessible to digital users, many new special-interest programs and a few local channels are using the inexpensive digital technology. Some smaller television providers send the television signal via DSL or fiber optic network through the Internet , where it is picked up by the operators of an uplink station (usually larger television stations) and transferred to the satellite. So are high transmission costs, such as. B. would arise in the expensive radio relay technology , avoided. In this way, the physical distance between the program provider and the broadcaster is easily overcome.
Thanks to the extensive expansion of the Internet and the introduction of ADSL2 as a new transmission standard, digital television can in future also be received directly from the Internet. Due to the high download rates with ADSL2 or fiber optics, the reception quality and interference resistance of the programs is just as high as e.g. B. via the classic cable or via satellite. Little by little, the vision of “worldwide television” would become reality, initially along broadband data networks.
The introduction of DVB-T , the terrestrial DVB variant, began at the beginning of 2003, a little later than in comparable countries (e.g. Great Britain 1996) . In August of the same year, Germany took on a pioneering role worldwide with the complete shutdown of analogue terrestrial television in the greater Berlin area . After Berlin, other metropolitan areas followed with the conversion to DVB-T. Since 2004, individual programs or test channels have been broadcast in the HDTV standard in Europe . Analog satellite television was switched off at the end of April 2012.
The opposite development is indicated in other countries: In Great Britain, for example, more and more programs are giving up their encryption. During the 1990s, most British television programs broadcast on the British Sky Broadcasting (BSkyB) platform , which, in addition to its own programs, also marketed third-party programs and provided them with basic encryption. Many of these providers, including the BBC and ITV, broke up with Sky and are now broadcasting unencrypted.
There are currently more than 120 unencrypted television programs destined for the UK market, including many full and specialty commercial programs. They are marketed under the labels Free-to-air (FTA, name for all unencrypted offers), Freesat (trademarked name for program packages from BBC and ITV) and Freeview (terrestrial DVB-T reception with around 30 programs). In order to withstand the competition, the pay-TV group BSkyB even put its own unencrypted, advertising-financed program into operation.
The encrypted offer from BSkyB ( Sky Digital ) is the most extensive in Europe and offers a large number of film, sports and entertainment channels as well as numerous special-interest channels from third-party providers such as Disney, Discovery, NBC Universal or Viacom. BSkyB belongs to the empire of media tycoon Rupert Murdoch ( News Corporation ).
Situation in other countries
Encrypted cable bouquets have become established in many European countries, most of which are fed entirely into the cable. Many broadcasters encrypt for licensing reasons because they have only acquired broadcasting rights for a limited broadcast area. These programs can be received free of charge, however, and decryption cards ( smart cards ) are usually sent to viewers free of charge.
In the Netherlands , all full programs encrypt their signal via satellite because all international productions, with the exception of some children's programs, are broadcast in the original language (with subtitles). Film and sport offers are marketed in the Canal Digitaal bouquet (cable, satellite). The major cable companies offer digital packages that include Canal Digitaal as well as international television brands such as Discovery and MTV . They are also provided with Dutch subtitles.
The situation is similar in Scandinavia and most of the countries of Eastern Europe, where the expense associated with synchronization would be economically unprofitable (exceptions: Russia, partly Poland). In order to avoid licensing problems, all programs are usually encrypted. The strong position of subscription television in these countries can also be explained by the small advertising market.
In Belgium , especially in Flanders , the digital programming offer is almost entirely concentrated on cable or ADSL. There is hardly any direct satellite reception. Chargeable digital packages (especially Teleclub ) are also offered in Switzerland via cable.
In France , three major pay-TV networks dominate, Canal Satellite numerique (better known as Canal + ), AB Sat and TPS ( Télévision par satellite ). TPS and Canal + merged in January 2006 and merged their offerings. All three in turn cooperate with numerous third-party providers, including the major national television broadcasters. Few programs are free to air in France.
Sky Italia , the dominant digital television provider in Italy, broadcasts via Eutelsat . Like BSkyB , it is ruled by Rupert Murdoch . Sky Italia emerged from the merger of the two former competitors STREAM and TELE +.
In Spain , the two digital platforms Vía Digital from Telefónica and Canal Satélite Digital from Sogecable merged to form the monopoly Digital + . The merger was due to a uniform program and structural policy and better earning opportunities. The market leaders AUNA and ONO dominate the cable market. Although almost all international productions in Spain are broadcast with Spanish synchronization, most national TV channels encrypt their programs via satellite. Recently, however, there has been an increased trend towards unencrypted broadcasting; especially regional networks and many special interest channels go this way. Former pay-TV channels are increasingly switching to advertising-financed broadcasting.
A basic fee for advertising-financed television offers is usually only available in the cable. However, some smaller program providers still prefer mixed funding, which relies on advertising and a low subscription fee. This basic subscription is, however, divided between a large number of special interest channels that are sold together in so-called basic packages. This mixed financing is common when a program cannot be operated economically through advertising income alone, for example because the broadcasting area or the target group are too small.
In the People's Republic of China and Cuba, digital terrestrial multimedia broadcast (based on the Chinese standard GB20600-2006), similar to DVB-T, is used for the digital broadcast of television programs.
Television on the internet
With the IPTV process ( Internet Protocol TV ), numerous television programs are already being distributed worldwide using the Internet Protocol. Over 200 topic channels are currently offered in German, which can be received via any web-enabled device with sufficient computing power. This includes information channels of larger companies such as brand manufacturers or travel agencies; In the meantime, however, many high-quality journalistic special-interest channels on a wide variety of topics are already offered.
The programs are still designed exclusively for Internet reception, but in the near future they can easily be integrated into cable bouquets or distributed in other ways. In future, the Internet can also be used purely as a transmission path; the processing and reception of services would then be the responsibility of the cable companies. IPTV is not yet designed for mass reception, but can be made mass-ready in just a few years by upgrading with multicast- enabled servers. Lately, a quasi-monopoly has been established around the Munich media entrepreneur Ingo Wolf , who offers or disseminates numerous special-interest programs based on IPTV technology, mostly unencrypted.
In the future, the Internet is likely to become a highly competitive area for all television providers, RTL and SAT1 / Pro7 will soon be broadcasting their programs on the Internet (see also IPTV ). Some network operators such as the cable provider HanseNet with its television bouquet Alice or Deutsche Telekom with its broadband transmission standard VDSL already offer IPTV television (including high-definition HDTV ) on the basis of IP multicast , but only within their own networks due to the currently insufficient Internet capacities.
Conversion from analog television to DVB-T
DVB-T is the abbreviation for the English term Digital Video Broadcasting Terrestrial and describes the terrestrial (terrestrial) distribution of digital radio, television and data signals in the earth's atmosphere . DVB-T is a variant of Digital Video Broadcasting (DVB) that is used primarily in various European, Asian and African countries as well as in Australia as the standard for the transmission of digital television and radio via antenna.
On February 1, 2003, digital terrestrial television signals were switched on for the first time in German-speaking Europe in Engadin, Switzerland. Berlin followed on August 4, 2003, and uniformly throughout Austria (Multiplex A) not until October 26, 2006. While analogue switch-off has now been completed in all three countries , the regional multiplexes (Mux C) are still being set up in Austria. In Germany there are private programs mainly in the urban areas of the so-called “start islands” (ie where the DVB-T conversion started), in Austria country-wide private television is also broadcast. In Switzerland, due to the high cabling quota, there is currently no need for private programs, which is why only a multiplex with four to five public service programs can be received there. In South Tyrol there is a wide range of Italian and German-language programs from all four countries, which are broadcast by the Südtirol Broadcasting Corporation , including, as in all of Italy, some programs in high-definition quality.
In Germany, four TV programs per multiplex are usually broadcast, in other countries more (five programs in German-speaking Switzerland) or fewer, plus radio programs (in Austria and partly in Germany) or HDTV content (e.g. in Italy) . In addition, from the start, Germany has relied on the establishment of single frequency networks (SFNs) and both UHF and VHF, while some other countries at least initially use multi-frequency networks (MFNs) or limit themselves to UHF.
The complete conversion to DVB-T, i.e. the abolition of analogue broadcasting of television programs, was planned in Germany by the decision of the federal government by 2010 at the latest. In general, the broadcast of analogue radio (television and radio) in the EU is to end in April 2012 (see analogue switch-off ).
In Europe, as in most countries in the world, transmission takes place in the DVB standard, which, in addition to television and radio programs, also includes additional information (e.g. subtitles, EPG ) and new data services (e.g. texts, PC data, MHP ) offers. There are different transmission options for DVB:
- DVB-T (terrestrial)
- DVB-C (cable)
- DVB-IPI (Internet)
- DVB-S (satellite)
- DVB-H (terrestrial for mobile devices).
The bandwidth of a typical transponder (satellite channel) on the well-known Astra broadcast satellite is mostly 33 MHz, which corresponds to a net data rate of 36 Mbit / sec or a symbol rate of 26 Msymb / s. A television station usually requires around 3–4 Mbit / sec, depending on its symbol rate (coding of 2 bits each to form a symbol). It ranges between 2.2 and 2.75 Msymb / s. Together with the error correction (usually 3/4 useful data to correction data), the required data rate results. The faster the image changes (changes in the image structure), the higher the required data rate. Sports and action scenes therefore require more bandwidth than motionless sequences (talk shows, etc.). If the bandwidth is calculated too narrow, artefacts (building block effects) occur when the scene changes quickly at a higher resolution.
Usually, radio programs with a data rate between 64 and 320 kbit / sec in the MPEG1-L2 standard as well as various data services are also transmitted via a transponder . Eight television programs in good quality can be conveniently transmitted via a pure television transponder, but only one analogue one. With the introduction of the more efficient MPEG-4 codec, compression will be even more effective in the future; more than 10 television programs can be transmitted per transponder while maintaining the same picture and sound quality. The time-consuming coding and decoding of the television signal leads to delays of several seconds compared to the analog broadcast. The more efficient the compression, the more complicated the coding algorithm.
With DVB, the television program is first encoded in MPEG-2, then the program is interlaced with any additional services in the multiplexer. Several programs (television, radio, etc.) within a package can be combined into a data stream, which is also called a transport stream . The data stream is then modulated with the carrier signal, amplified and directed to the transmitter or satellite or to the cable head end.
The following table explains the differences between analog and digital television based on individual aspects.
|Noise component The signal-to-noise ratio depends on the strength of the received signal||Due to error correction, noise leads to few, but strong, dropouts|
|no compression of the brightness information||Compression with MPEG-2 or MPEG-4|
|only fields ( interlaced )||Fields and frames|
|Colors are transmitted with a lower horizontal bandwidth (with SECAM also vertically)||Colors are transmitted with low horizontal and vertical bandwidth|
|Frequency bands ( frequency band ) are assigned to transmitters||Frequency bands and dynamic time “packets” are assigned to transmitters|
|The image parameters (number of lines, number of columns, frequency) are defined by the hardware||The image parameters are limited by the receiver computing power. The compression factor ( data compression ) is dynamic.|
|The sound is frequency-modulated, requires less transmission power than the image information, but increases the bandwidth requirement||The sound is contained in the digital data stream and thus increases the data rate requirement.|
|Teletext is inserted in the blanking interval||Teletext is contained in the digital data stream.|
|fixed bandwidth and signal-to-noise ratio (S / N)||Bandwidth and signal-to-noise ratio can be exchanged for one another. To reduce the transmission power, the S / N is usually selected to be weaker and a suitable filter in the receiver allows more effective bandwidth.|
Digital usage market share
- Eric Karstens: Digital TV. An introduction . VS-Verlag, Wiesbaden 2006, ISBN 3-531-14864-8 .
- Frank Zervos: Digital TV in Germany. Media-political and media-economic challenges of future television . VS-Verlag, Wiesbaden 2003, ISBN 3-531-14027-2 .
- Dominik Eggert, Ralf Kaumanns, Veit Siegenheim: Preferences of European and American users with regard to analog and digital television In: Media Perspektiven 01/2009, pp. 20–29 (PDF; 287 kB)
- Siegbert Messmer: Digital TV in Germany. An industrial economic analysis of the need for economic policy action . Publishing house Peter Lang, Frankfurt / M. u. a., 2002, ISBN 3-631-38888-8 .
- Link catalog on the subject of digital television at curlie.org (formerly DMOZ )
- DVB-T conversion scenarios
- DVB-T conversion scenario for East Westphalia: conversion from analogue broadcasting to digital broadcasting using the example of East Westphalia for DVB-T. On a set date, the analogue broadcasting is stopped and the digital broadcasting activated. To do this, the old analog transmitter system is replaced by a new digital transmitter system by helicopter within a few hours. It can be seen from the comments on this article that some people were surprised by the switch. The local press had barely paid attention to the subject.
- DVB-T conversion scenario for Bavaria: Switchover from analogue broadcasting to digital broadcasting using the example of DVB-T in Bavaria: "On May 30th, broadcasters such as ProSieben, Sat.1 or RTL will cut analogue broadcasting via antenna throughout Bavaria."
- DVB-T conversion scenario for Baden-Württemberg and Rhineland-Palatinate: “In May” 2006, “in the greater Stuttgart, Mannheim, Ludwigshafen, Heidelberg, Upper Palatinate and Kaiserslautern (...) analogue terrestrial antenna television (...) will switch to digital quality (DVB-T) changed. (...) In Heidelberg, Mannheim, Ludwigshafen and the Vorderpfalz, the so-called 'hard changeover' will probably take place on May 17th, when the two broadcasters Königstuhl and Weinbiet will only broadcast digital program signals. (...) After the "switch in the starting islands", the further expansion of DVB-T in Baden-Württemberg and Rhineland-Palatinate will follow step by step. According to the ideas of SWR and ZDF, the changeover should be completed nationwide by the end of 2008. "
- DVB-T conversion scenario for Hesse: hr-online.de: "Starting signal for DVB-T in all of Hesse on May 29, 2006. (...) analogue broadcasting via antenna will be discontinued in Hesse on May 29, 2006" (tough switch ).
- heise.de: Antennenfernsehen in Deutschland digitized , December 10, 2008, accessed on December 24, 2011
- France: Groupe Canal + and TPS merged
- GRADE OF DIGITALIZATION Reporting households | url = https://www.agf.de/daten/tvdaten/digitalisierungsgrad/ retrieved on January 9, 2020
- Digitization Report 2019 (PDF; 3.81 MB) Data and facts
- Digitization Report 2019 . (PDF; 3.8 MB) Data and facts
- Digitization Report 2018 . (PDF; 6.9 MB) Data and facts
- Digitization2017 . (PDF; 1.97 MB) Data and facts
- Digitization2016 . (PDF; 2.1 MB) Data and facts
- Digitization2015 . (PDF; 2.0 MB) Data and facts
- Digitization2014 . (PDF; 2.41 MB) Data and facts
- Digitization2013 . (PDF; 8.8 MB) Data and facts
- Digitization2012 . (PDF; 7.4 MB) Data and facts
- Digitization2011 (PDF; 1.65 MB) Data and facts
- Digitization2010 (PDF; 3.8 MB) Data and facts
- Digitization2009 (PDF; 3.8 MB) Data and facts
- Digitization2008 (PDF; 5.0 MB) data and facts
- Digitization2007 (PDF; 1.7 MB) data and facts
- Digitization2006 (PDF; 1.9 MB) Data and facts
- Digitization2005 (PDF; 3.6 MB) data and facts