Digital Video Broadcasting

Digital Video Broadcasting (DVB) [ dɪdʒɪtəl vɪdiəʊ bɹɔ ː d ˌ kɑ ː stɪŋ ] stands for Digital Video Broadcasting.

Technical DVB is the standardized process for transmitting digital content (TV, radio, surround sound, surround sound, interactive services such as MHP, EPG and Teletext, and other supplemental services) through digital technology. Through data compression (MPEG -2 and H.264 for HDTV especially ) more programs per transmission channel (frequency ) can be transmitted compared to analog television transmission. The quality is highly customizable; the more the data is compressed, the more programs can be simultaneously transmitted on a transponder ( satellite), in turn decreases the quality or increasing the computational effort.

Furthermore, as subscribers or pay- TV, pay -per-view, video-on -demand by encrypting the signal for the transmitter are much cheaper and safer deals possible.

Transmission paths

There are several technical sub-species of DVB for the different transmission paths, which mainly depends crucially on the optimal choice from the frequency domain and in the transmission channel modulation method, and differ in the error correction:

• DVB -S for transmission by direct radiating satellite
• DVB -S2 current successor standard for DVB -S
• DVB -C for transmission over cable networks ( Cable)
• DVB -C2 successor standard for DVB -C
• DVB- T for transmission by terrestrial broadcasting networks in the VHF or UHF range
• DVB -T2 successor standard for DVB- T
• DVB -H for asynchronous transmission to mobile devices ( handhelds), also terrestrial
• DVB- IPI for transmission over IP-based networks, such as Internet (Internet Protocol Infrastructure)
• DVB -RC (S / C / T) back channel ( return channel ) for the transmission of data services, such as broadband Internet
• DVB -SI service information for the transmission of
• DVB -SH for transmission via satellite to mobile devices

Equipment requirements in the audience

Must the vast number of existing televisions and VCRs can not deal directly with the digital signals, making them suitable for a digital receiver ( as a set -top box, STB ) to receive the data, decode and convert it into an understandable for the older electronics analog signal. But then comes the example ARD and ZDF lost existing high image quality in DVB -S and DVB- C signal, as to full-fledged digital TV reception also includes a digital video connection on the receiver and on the screen, ie with an HDMI cable.

Meanwhile, there are also televisions with fixed or optional receiver technology for DVB -C ,-S, and T on the market ( see also IDTV ). For the mobile DVB- H reception there on principle only fully integrated new equipment, often mobile phone combinations. There are also plug-in cards and USB devices (see also DVB -T stick ) for computers and laptops, which often themselves take only the reception and given the task of decoding and displaying the computer.

History and Background

In the European DVB project over 270 member companies have joined together to promote digital television. American, Japanese and Korean companies are involved through their European subsidiaries, more come from Australia and Canada. The members are broadcasters, manufacturers, network operators and authorities. The European Commission (Commission of the European Communities, CEC), and other associations and standardization bodies such as ETSI and CENELEC are involved in the work. Under a cooperation contracts was agreed that ETSI and CENELEC assume the costs entailed in DVB Project technical specifications. As a result, the specifications to the general public free of charge from the ETSI website available. In the work of the Moving Pictures Expert Group (MPEG ) was included, which can standardize their work in the organizations ISO and IEC. Therefore, the results of the MPEG group are published there.

DVB -S and DVB -C were ratified in 1994, DVB- T early 1997.

Driving basic concepts for the introduction of digital television technology are:

• The number of TV programs per channel can be multiplied ( bouquet ).
• Encryption methods for pay-TV are easier and safer to implement.
• Additional distribution of radio programs is possible.
• Transferring ( also interactive ) data services (see also MHP) in the context of the programs offered.
• Picture and sound quality can be increased, so that a viewer who has a high quality TV, select also broadcasts in High Definition and receive (HDTV). Even on non- high-definition TVs, the digital technologies allow a much poorer image noise and ambience.

See also: DAB, DRM, DTV, VDR, ISO 6937

Current situation of DVB

Distribution and content

When radiation DVB programs via satellite, there is a wide range of programs and all the German-speaking free to air stations now broadcast via DVB -S with no additional monthly charges. Exceptions are some regional and local stations or windows that are spread via antenna TV or cable TV.

DVB- T has already been established in the areas where this transmission technology is available (see also conversion for DVB -T).

DVB -H has already been tested in many test networks to the entire world and introduced commercially in some countries at this time.

In the diffusion of DVB -C, however, there were in Germany at the major cable providers some problems. Long as there was no nationwide broadcast of private TV channels via DVB -C. Only the public broadcasters as well as Sky and other pay-TV offerings were to receive. Since January 2006, the reception of stations RTL and ProSiebenSat.1 family is also digitally possible after the cable companies could agree with the transmitters. This above all other distribution channels are free to air programs grundverschlüsselt ( exception: network of Kabel BW ) and can be seen in some cable networks only with an additional fee. It is usually a one time fee, but there are also cable operators that charge a monthly fee. There are some smaller private cable operators, often in more rural regions, from the beginning and for no additional fee DVB satellite signals of the great German families of channels like ARD, ZDF, RTL, ProSiebenSat.1 and of course Sky and some other English channels (DSF, Tele 5 etc. ) have fed into the cable network and still do, even if it takes here a DVB- C receiver - so need Sky customers here, for example, while a smart card.

In part, the cable operators also demand also means that for the reception of DVB - C channels basically the serial number of a Sky -certified receiver must be specified, even if no Sky subscription exists or is desired.

Digital TV (DVB) has the analog television completely replaced (see also analogue switch-off ).

Technology

Several transmitted via DVB TV and radio programs share a channel or transponder. The data streams of the individual programs will be to produce a total data stream " muxed" (derived from " multiplexer "). Each channel data rates 2 Mbit/s-8 Mbit / s are common and HDTV programs up to 27 Mbit / s, it being noted that the video bit rate is often variable, and the maximum value is usually achieved not permanent, while the audio and other data streams having a constant bit rate; e.g. 256 kbit / s for standard MP2 audio as TV sound or radio program.

Compared to analogous radiation the DVB signal reaches the TV sets with clearly perceptible delay. This phenomenon caused during the soccer World Cup 2006 to irritation, as from analogue TV households often supplied goal celebration could be heard, while DVB- users got to see the triggering scene a few seconds later.

See also: DVB service information

Differences

DVB -S ( satellite)

• Modulation: QPSK
• Transmission capacity: typically 33 Mbit/s-38 Mbit / s
• Reception: Satellite Dish
• Mobility: stationary, conditionally portable ( mobile)
• Return channel / other: No / telephone networks

DVB -S2 (satellite, HDTV)

• Types of modulation: QPSK, 8PSK, 16APSK or 32APSK

DVB -C (cable)

• Types of modulation: 16-256 QAM
• Transmission method: QAM
• Transmission capacity: typically 38 Mbit / s ( 64 QAM)
• Reception: Broadband network connection
• Mobility: stationary
• Return channel / other: yes / telephone networks

DVB -C2 (cable)

• Modulation types: 16-4096 QAM
• Transmission method: COFDM
• Transmission capacity: typically 38 Mbit / s ( 64 QAM), 83 Mbit / s ( 4096 QAM)
• Reception: Broadband network connection
• Mobility: stationary
• Return channel / other: yes / telephone networks

DVB- T (terrestrial )

• Types of modulation: QPSK, 16- QAM, 64- QAM
• Transmission method: COFDM
• Transmission capacity: typically 4 Mbit/s-22 Mbit / s
• Reception: depending on the location and room, outdoor or roof antenna
• Mobility: stationary, portable, mobile
• Return channel / other: yes / telephone networks

DVB- T2 ( terrestrial)

• Complete standardization, first field trials.

Criticism

Because digital signals can be encrypted simply, the shift of the market of free TV is favored towards paid content.

Also critics see the possibilities of free access and the anonymous use of the media ( Free-To- Air) through the use of digital methods and thereby possible digital rights management (DRM ) through smart cards, HDCP severely restricted, and the like.

Where on a transponder only an analogue TV channel is broadcast, some digital channels can be used because of its data compression in the same frequency range. Therefore, the analogue satellite channels are different from the introduction of DVB- T is not threatened from bandwidth reasons of the closure, but decide it mainly economic considerations on the part of the sender ( and partly also on the side of the satellite operator ) whether and when analogue satellite channels are set; so to be (eg Entavio ) forced to DRM -enabled systems about to make migration of viewers.

In the operation of set- top boxes for television reception ( digital receiver, satellite receiver) to conventional televisions, video and DVD recorders with terrestrial television receiver section, there are some limitations. These problems are due to the fact that the conventional recording devices also have only analog tuners, and are not prepared for DVB reception. (Excluding still prevails analog technology in cable TV in Germany ) As part of the overall DVB- conversion, there are now an increasing number of televisions with integrated (partially modular ) DVB reception parts; for easy recording of DVB programs are hard disk recorder with DVB reception part available.

Because of the interest of the owner of such protection of the irradiated material prior to high-quality copies is planned with built-in DVB - receiving part that the sender can send them along a signal that prohibits or restricts the recording broadcast as for new DVD or hard disk recorder. The recorder manufacturer could then be committed in parallel to modify their recorder technically so that this signal is evaluated with an uptake and thus may prevent a recording - similar to the Macrovision copy protection for physical media.