Digital Television (DTV) is an information service platform that provides digital signals for TV programs, emission, transmit and television. Compared with the analog television, DTV enjoys the following characteristics and advantages in technology, Firstly is its high definition, good audio effects and strong anti-jamming ability.
Secondly, channel numbers will be multiplied. Using the existing 8MHz analog TV channel can transmit the DTV programs with 6-8 channels of DVD level or 15-18 channels of VCD level. The full use of TV channel resources is able to meet the personalized demands of consumers for free choices of TV programs.
Thirdly, multi-purpose services can be developed. As CATV transmission and users' access get gradually digitized, it is much easier for the development of new services such as TV websites, interactive TV, stock market and analysis and video on demand, etc, and then the users will change from simple viewers into the active participators.
Globally, the first DTV broadcasting for commercial purpose appeared in France in Apr 1996 and then it rapidly spread all over the world. The number of global DTV users has reached 220 million in 2006, and the average penetration rate of DTV came to 20%, among which Europe, US and Japan took high shares. Currently, all the countries of the world have successively put the DAC (Digital/Analog Conversion) into schedule. The Netherlands has stopped the broadcasting of analog TV programs since Dec 2006, which became the first one to completely use DTV signals. Northern European countries plan to stop these by 2007 while U.S. and Japan plan to say goodbye to analog TV by 2008 and 2011 respectively. And China plan to fulfill DAC by 2015.
In 1985, China began to transmit the programs of CCTV all over the country through telecommunication satellite. Satellite live TV adopts satellite digital compressed technology to transmit broadcasting/TV programs, which can improve the qualities of signal sources of CCTV or provincial TV programs that would be re-broadcasted in the local TV stations, and then rapidly expand the population coverage rate of broadcasting and TV programs.
According to the statistics, by the end of 2006, there have been 24 cities that have finished the overall conversion of making CATV digitized. On the basis of previous Qingdao model, Hangzhou model, Foshan model and Shenzhen model, some successful models like Guangzhou model and Guangxi model appeared again.
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