digital video broadcasting (DVB)
What is digital video broadcasting (DVB)?
Digital video broadcasting (DVB) is a set of standards that define digital broadcasting using DVB satellite, cable and terrestrial broadcasting infrastructures.
In the early 1990s, European broadcasters, consumer equipment manufacturers and regulatory bodies formed the European Launching Group (ELG) to discuss introducing digital television (DTV) throughout Europe.
The ELG realized that mutual respect and trust had to be established between members, and later became the DVB Project. There are different DVB standards, including the following:
- DVB-T, DVB-T2 for digital terrestrial television
- DVB-C and DVB-C2 for cable television
- DVB-S and DVB-S2 for satellite television
- DVB-SH for microwave
The specifications were approved by the DVB Steering Board for different purposes. These are used by TV channels, broadcasting systems and broadband networks.
Today, the DVB Project consists of over 220 organizations in more than 29 countries worldwide. DVB-compliant digital broadcasting and equipment are widely available and are distinguished by the DVB logo.
Numerous DVB broadcast services are available in Europe, North and South America, Africa, Asia and Australia. The term digital television is sometimes used as a synonym for DVB. However, the Advanced Television Systems Committee (ATSC) standard is the digital broadcasting standard used in the U.S.
How digital video broadcasting works
Unlike analog television, digital televisions transform data into "packets" of compressed data. The data is subject to encoding and decoding, which ensures high-quality multimedia without the lag faced by analog television broadcasting.
DVB networks rely on their interactivity solutions, a limited set of return channels and relevant specifications for the multipoint distribution of data.
A fundamental decision of the DVB Project was the selection of MPEG-2, one of a series of MPEG standards for compression of audio and video signals. MPEG-2 reduces a single signal bandwidth from 166 Mbps to 5 Mbps, allowing broadcasters to transmit digital signals using an existing cable, satellite and terrestrial systems.
MPEG-2 uses the lossy compression method, which means the digital signal sent to the television is compressed and some data is lost. This lost data does not affect how the human eye perceives the picture.
Two digital TV formats that use MPEG-2 compression are standard-definition television (SDTV) and high-definition television (HDTV). SDTV's picture and sound quality are similar to digital versatile disks (DVD). HDTV programming presents five times more information to the eye than SDTV, resulting in cinema-quality viewing.
Increased security with digital video broadcasting
DVB uses conditional access (CA) systems to prevent external piracy. There are numerous CA systems available to content providers, allowing them to choose the CA system they feel is adequate for the services they provide.
Each CA system provides a security module that scrambles and encrypts data. This security module is embedded within the receiver or is detachable in the form of a PC card. Inside the receiver, there is a smart card that contains the user's access information. The following describes the conditional access process:
- The receiver receives the digital data
- The data flows into the conditional access module, which contains the content provider's unscrambling algorithms.
- The conditional access module verifies the existence of a smart card that contains the subscriber's authorization code.
- If the authorization code is accepted, the conditional access module unscrambles the data and returns the data to the receiver. If the code is not accepted, the data remains scrambled, restricting access.
- The receiver then decodes the data and outputs it for viewing.
For years, smart cards have been used for pay-TV programming. Smart cards are inexpensive, allowing the content provider to issue updated smart cards periodically to prevent piracy. Detachable PC cards allow subscribers to use DVB services anywhere DVB technology is supported.
Use of digital video broadcasting in the future
DVB is an open system as opposed to a closed system. Closed systems are content provider-specific, not expandable and optimized only for television. Open systems such as DVB allow the subscriber to choose different content providers and allow the integration of PCs and televisions.
DVB systems are optimized for not only television but also for home shopping and banking, private network broadcasting and interactive viewing. DVB offers the future possibilities of providing high-quality television displays in buses, cars, trains and hand-held devices.
DVB allows content providers to offer their services anywhere DVB is supported regardless of geographic location, expand their services easily and inexpensively, and ensure restricted access to subscribers, thus reducing lost revenue due to unauthorized viewing.
See also: streaming video, streaming media, orthogonal frequency-division multiplexing (OFDM), ATV (advanced television), Internet Protocol television and video telephony.
