Tag: Digital TV Analog TV
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Three core analysis of digital TV transmission standards
Depending on the region, transmission method and modulation method, the transmission method needs to be matched with different modulations to have the best effect. First, let us first look at the major transmission standards in the world where satellite transmission is DVB. -S standard, digital cable TV is the DVB-C standard and is the most popular terrestrial digital broadcasting system. For example, the United States adopts the ATSC (Advanced Television System Committee Advanced Television System Committee) standard, and the European standard is DVB. (DigitalVideo Broadcasting Digital Video Broadcasting); Japan's standard is ISDB (IntegratedServiCESDigital Broadcasting Integrated Services Digital Broadcasting).
Modulation and transmission method / China adopts DMB-TH transmission standard
On August 18, 2006, China determined the digital TV terrestrial broadcasting transmission system standard--GB20600-2006 "Digital TV terrestrial broadcasting transmission system frame structure, channel coding and modulation", and will be enforced on August 1, 2007. The standard name is DMB-TH, which is the ADTB-T integration scheme of DMB-T and Shanghai Jiaotong University promoted by Tsinghua Tongfang.
Analysis of the difference between video and audio coding of analog and digital TV
The biggest difference between traditional analog TV and digital TV is the change of video coding. Digital TV transmits digitally encoded video and audio, while analog is a hybrid analog transmission. Digital signal has an absolute advantage in terms of information loss.
The current digital video coding is mainly based on mature MPEG2, which is also the most popular encoding of DVD video, as well as H.264, WMV, etc. The audio coding is mainly based on AC3, AAC, MPEG2, etc. Good or bad is judged by the performance of the image transmitted under the same bandwidth. For example, H.264 is better than MPEG2, and can achieve higher image quality on a smaller bandwidth. In digital TV, this It's important because the new code can achieve high-definition display without adding more bandwidth. But in China, it's not so good to use anything, you need to consider coding license fees, terminal equipment costs and compatibility. Factors, so there is still a lot of resistance to the current high definition of HD.
Digital TV will adopt a new encryption system
Unlike traditional analog TV, digital TV has a good job in encryption. The cable cards that were previously used for payment will need to be plugged into the set-top box to be able to watch TV programs normally. The digital TV encryption system greatly enhances the TV operator. The income security, users who open the charging service need to insert the user card into the set-top box and the digital all-in-one to watch the program, and the current digital cable TV encryption system does not unify the set-top box products can not be sold nationwide, forming a certain local trade barrier. .
In addition, digital TV is still based on the original cable TV. By installing a set-top box, the wired RF cable is connected to the set-top box, decoded by the set-top box and then output to the TV, and the program can be normally viewed.
Is digital TV transmitted in several ways?
To put it simply, digital TV can be accessed through satellite, terrestrial broadcasting, cable TV systems, and broadband. The following is an introduction to these transmission methods.
Satellite transmission
Satellite TV is not new to some enthusiasts, but for the general public, it is more mysterious. In fact, the use of satellite TV is very simple, only need one receiver box and one antenna (commonly called "pot"), and then After adjusting the parameters of the search star, you can watch the adjustment method normally and refer to some corresponding instructions.
Satellite receiver
The use of satellites is a very good choice, but it is subject to corresponding restrictions. For example, different satellite coverage areas are limited. It is not a place where friends or friends in any direction can use them normally. It is illegal for Chinese individuals to use satellite TV. So it is not popular.
Terrestrial broadcast transmission
Digital terrestrial broadcasting is more commonly used in China as a terrestrial broadcast transmission standard. Similar to the early years of wireless TV, it is simply that the TV tower's TV tower transmits signals and then covers a certain range of cities. For example, mobile TVs used in many areas are adopted. This transmission standard is received.
Schematic diagram of DMB-T/H transmission system
The national standard enforced this standard and gradually upgraded it and upgraded it. It has become a standard for terrestrial digital broadcasting announced by the Ministry of Information Industry of China now - DMB-T/H, which is the DMB-T and the promotion of Tsinghua Tongfang. Shanghai Jiaotong University's ADTB-T integration program.
Wired and broadband
Wired and IPTV are easier for users who often watch TV and Internet, and the manufacturers are mainly telecom departments rather than broadcasting. From the characteristics of TV broadcasting, the current XDSL is not suitable for point-to-multipoint transmission, and maybe wait until later. Fiber-to-the-home and triple play are more potential when they become a reality.
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