The development of digital TV and its standards

The development of digital TV and its standards


1. What is digital TV? Digital TV concept
Digital TV refers to a new TV system that uses digital TV signals or processes and modulates digital TV signals from the studio to the transmission, transmission, and reception. All signal propagation of the system is propagated through a digital stream composed of 0 and 1 digital strings. The propagation rate of digital signals can reach 19.39M bytes per second. Such a large data stream ensures high definition of digital TV. Degree, overcame the inherent shortcomings of analog TV.
2. The two mainstream interpretations of digital TV (1) In the 1980s, ITT developed a set of digital processing chips. When receiving analog TV signals, they are processed by analog high and intermediate frequency, and finally converted into digital signals by analog / digital Perform digital processing to improve image clarity. In the 1990s, a variety of "digital TVs" with picture-in-picture, double lines, and other improvements appeared, but these TVs still received analog TV signals, not digital TV in the true sense.
(2) "Digital TV" (DTV for short) in the United States refers specifically to terrestrial digital television broadcasting systems. In this system, in addition to a part of the current program production is analog, all links from the studio to the transmission, transmission and reception are using digital TV signals. Therefore, only this kind of TV is a veritable digital TV.
3. The advantages of digital TV Digitalization is a technological transformation of the radio and television industry, which will bring a revolution to radio and television. The digitalization of cable TV mainly brings three changes:
(1) Change in quantity. Now 30 to 50 TV programs can be seen through the cable TV network. After digitizing, you can see hundreds of TV programs.
(2) Qualitative changes. After digitization, our TV sets have become multimedia information terminals, which can not only watch TV programs, but also listen to broadcasts, can obtain a variety of information and information services, and can be used for TV shopping, water and electricity bills, etc. Tools have become the supporting platform for the modern social service industry.
(3) Change of method. Now watching TV is passive watching. After digitization, we can actively watch and choose the programs we like to watch according to our own time. It can be said that while the digitalization of radio and television meets public needs and general requirements, it provides users with a pair of

1. End-to-end personalized service.
4. Disadvantages of digital TV Digital TV is not perfect, it also has some weaknesses. For example, the signal damage caused by the sampling process, quantization error, and compression coding is passed through during the production and transmission of the program. Some damages can be repaired without affecting the final quality of the image, while some damages can only be weakened by some compensation measures, but this does not affect the TV field to digital transformation.
5. Classification of digital TV ● According to the signal transmission method, it can be divided into: ground wireless transmission digital TV; satellite transmission digital TV; cable transmission digital TV.
● According to the image definition, it can be divided into three categories: digital high-definition television (HDTV); digital standard definition television (SDTV); digital ordinary definition television (LDTV).
● According to product type, it can be divided into: digital TV monitor, digital TV set-top box and integrated digital TV receiver.
● Classification according to the aspect ratio of the display screen: digital TV can be divided into two types: 4: 3 and 16: 9 aspect ratio.

Second, the digital TV standard In the digital TV transmission code stream, how big a packet is, how many bytes it contains, what is the meaning of each byte, and even what is the meaning of a bit of a byte, there is a clear Regulations, this is the standard. There are three types currently in use: ATSC (Advanced Television Systems Committee) in the United States; DVB (Digital Video Broadcasting) in Europe; ISDB (Integrated Services Digital Broadcasting) in Japan.
Each digital TV standard can be divided into satellite transmission, cable transmission and terrestrial transmission.
1. American ATSC Standard The ATSC digital TV standard consists of four separate levels with clear interfaces between the levels. The highest layer is the image layer, which determines the form of the image, including pixel array, aspect ratio and frame rate. The second layer is the image compression layer, which uses the MPEG-2 image compression standard. The third layer is the system multiplexing layer. Specific data is included in different compressed packages, such as program 1 image, program 2 sound, or auxiliary data, using the MPEG-2 system standard. The last layer is the transmission layer, which determines the modulation and channel coding scheme for data transmission. For terrestrial broadcasting, the standard adopts 8VSB developed by Zenith. This system can achieve a transmission rate of 19,3Mb / s through a 6MHz terrestrial broadcasting channel. The standard also includes a 16VSB mode suitable for the high data rate of cable TV systems, which can achieve a transmission rate of 38.6Mb / s in a 6MHz cable channel. The lower two layers share common data transmission, and the upper two layers determine the specific configuration that runs on the basis of ordinary data transmission, such as HDTV or SDTV (standard definition television). The above two layers also determine the specific image formats supported by the ATSC standard, a total of 18 formats (6 HDTV, 12 SDTV), 14 using progressive scanning.
(1) HDTV, 1920 pixels (H) x 1080 pixels (V), aspect ratio 16: 9, frame frequency 60Hz / interlaced scanning system, frame frequency 30Hz and 24Hz / progressive scanning system;
(2) HDTV, 1280. Pixel (H) X720 pixel (V), aspect ratio 16: 9, frame rate 60Hz and 30Hz, 24Hz / progressive scanning system;
(3) SDTV, 704 pixels (H) x 480 pixels (V), aspect ratio 16: 9 or 4: 3, frame frequency 60Hz / interlaced scanning system, frame frequency 60Hz and 30Hz, 24Hz / progressive scanning system;
(4) SDTV, 640 pixels (H) x 480 pixels (V), aspect ratio 4: 3, frame frequency 60Hz / interlaced scanning system, frame frequency 60Hz, 30Hz, 24Hz / progressive scanning system.
Except for one HDTV, the image format uses progressive scanning. Because the 1920x1080 format is not suitable for progressive scanning at 60 frames per second in a 6MHz channel, it is replaced by interlaced scanning. The 640x480 image format of SDTV is the same as the VGA format of the computer to ensure the applicability with the computer. Among all 12 SDTV formats, 9 types use progressive scanning, and 3 types are reserved for interlaced scanning to adapt to existing video systems .
In addition, ATSC has also developed a separate standard for use in countries with a frame rate of 50 Hz. The pixel array of HDTV is the same, but the frame rate is 25Hz and the vertical resolution of the 50Hzo SDTV format is 576 lines and the horizontal resolution is different; it also contains the 352x288 format to adapt to the necessary window settings. The ATSCDTV standard based on the 50Hz version makes it easier for countries with frame rates of 50Hz.
There are 30 ATSC members, and China's Academy of Broadcasting Science also participated in the ATSC organization.
2. European DVB standard
DVB standards include: DVB broadcast transmission system, DVB baseband additional information system, DVB interactive business system, DVB conditional access and interface standards. details as follows:
(1) DVB broadcast transmission system DVB digital broadcast transmission system uses all general TV broadcast transmission media including satellite, cable, terrestrial, SMATV, MNDSD. They correspond to the DVB standards: DVB-S \ DVB-C, DVB-T, DVB-SMATV, DVB-MS and DVB-MC.
1) DVB-S (ETS 300421) ?? Digital satellite direct broadcast system standard.
The standard uses satellites as the transmission medium. The compressed digital signal forwarded by the satellite is processed by the satellite set-top box after passing through the satellite receiver, and outputs a signal that can be received by the existing analog television. The modulation of the data stream adopts four-phase phase shift keying modulation (QPSK) mode, and the operating frequency is 11 gates 2GHz. When using the MPEG-2 MP @ ML (main class @ main level) format, the code rate of the client to achieve CCIR601 studio quality is 9Mb / s, and the code rate to achieve PAL quality is 5Mb / s. The transmission rate of a 54MHz transponder can reach 68Mb / s, and can be multiplexed by multiple programs.
After the DVB-S standard was announced, almost all satellite live digital TVs adopted this standard, and China also adopted the DVB-S standard.
2) DVB-C (ETS 300 429) ?? Digital cable broadcasting system standard.
The standard has three methods of 16, 32 and 64QAM, and the operating frequency is below 10GHz. When using 64QAM quadrature amplitude modulation, the transmission rate of one PAL channel is 47.34Mb / s, which can also be used for multiple program multiplexing. In 2001, the industry standard "Code and Modulation for Cable Digital TV Broadcast Channels" promulgated by the State Administration of Radio, Film and Television is equivalent to the DVB-C standard.
3) DVB-T (ETS 300 744) ?? Digital terrestrial broadcasting system standard.
This is the most complex DVB transmission system. Now it adopts Coded Orthogonal Frequency Division Multiplexing (COFDM) modulation method, which can transmit 4 sets of TV programs within 8MHz bandwidth, with high transmission quality and few channels.
4) DVB-SMATV (ETS 300 473) ?? Digital SMA'IV (satellite shared antenna TV) broadcasting system standard. 5) DVB-MS (ETS 300 748)?-Digital broadcasting MMDS distribution system standard higher than 10GHz.
MMDS is a system that uses amplitude modulation microwave to transmit to multiple points and distribute multi-channel TV programs. The standard is based on DVB-S, which allows microwave signals carrying a large number of programs to enter the home directly. A DVB-S receiver can be used with a MMDS frequency converter to receive DVB-MS signals.
6) DVB? MC (ETS 300 749) ?? Digital broadcasting MMDS distribution system standard below 10GHz This standard is based on DVB-C, which allows microwave signals carrying a large number of programs to be directly entered into the household. A DVB-C receiver can be used with a MMDS frequency converter to receive DVB-MC signals.


(2) DVB baseband additional information system In addition to transmitting ordinary video \ audio signals, the DVB digital broadcasting system also needs to transmit and receive old D tuning, program guides, and information such as graphics, subtitles, and icons.
1) DVB-S1 (ETS 300.468) ?? Digital broadcasting service information system standard.
The standard consists of a series of tables and descriptors that give all the parameters related to DVB services or programs.
2) DVB-TXI (ETS 300 472) ?? Digital teletext broadcasting system standard.
This standard is used for fixed format teletext transmission.
3) DVB-SUB (ETS 300 743) ?? Digital broadcasting subtitle system standard.
This standard is used for the transmission of subtitles and icons (station logos, etc.).
(3) The DVB interactive business system is based on the general DVB digital broadcasting system. The elements of the interactive business system include an independent protocol for the interactive business network compatible with other relevant international standards, a return channel for transmitting interactive service process commands and control signals Wait.
1) DVB-N, P (ETS 300 802) / DVB interactive service network independent protocol standard.
2) DVB? RCC (ETS 300 800)-CALX / system DVB backhaul channel standard.
3) DVB? RCT (ETS 300 801)-PSTN / ISDN DVB backhaul channel standard.
(4) DVB conditional access and interface standards Some services in DVB digital broadcasting systems transmit scrambled conditional access information. The universal interface for conditional access enables the IRD (Integrated Decoding Receiver) to descramble scrambling information using a general scrambling algorithm. The connection of the DVB digital broadcasting system with other telecommunication networks (such as PDH, SDH, ATM, etc.) expands the application scope of the DVB technology, and its interface with these telecommunication networks enables the transition from DVB to telecommunication networks. There are also interfaces for connecting professional equipment and old D.
1) DVB-CI (EN 50221) ?? Universal interface standard for conditional access and other applications o
2) DVB? PDH (ETS 300 813)-PDH (quasi-synchronous digital series) network DVB interface standard o
3) DVB-SDH (ETS 300 814)-SDH (synchronous digital series) network DVB interface standard.
4) DVB-ATM (ETS 300 815)-ATM network DVB interface standard.
5) DVB? PI (EN 50083-9)-CA-IV / SMAIV front-end and similar professional equipment interface standards.
6) DVB? IPDI (EN 50201) wDVB? IRD interface standard.
DVB members have reached 265, including China's Broadcasting Research Institute and TCL Electronics Group.
3. Japanese ISDB standard ISDB is a digital broadcasting system standard formulated by Japan ’s DIBEG (Digital Broad? CasTIng Experts Group). It uses a standardized multiplexing scheme to send various types of transmission on a common transmission channel. At the same time, the signals that have been multiplexed can also be sent through various transmission channels.
It can be predicted that in the near future ATSC, DVB, ISDB and other digital TV standards will no longer exist, replaced by a unified international digital TV standard.

3. Digital TV in China The development of China's digital TV Since the Ministry of Science and Technology approved the implementation of China's major high-definition television major technology industry engineering project in 995, China's digital TV has experienced ten years of development and achieved world-renowned achievements. Since 2000, the country has set up a special project on digital TV R & D and industrialization, focusing on the research and formulation of national digital TV standards, digital TV industrialization and application promotion experiments with independent intellectual property rights, including the approval of three test areas in Beijing, Shanghai and Shenzhen 2 test laboratories have approved a series of industrial development projects. The development plan of digital TV has been included in the 12 major special projects of the "Tenth Five-Year Plan" high-tech, and the research work of digital TV has been fully launched.
2. China's Digital TV Standards Currently, China's digital TV-related standards are as follows:
(1) Digital (high definition) television standard system.
(2) The basic standards of digital TV are as follows:
1) GB / T7400.11 digital TV terminology; 2) GY / T134 digital TV image quality subjective evaluation method; 3) GY / T144 broadcast TV SDH trunk network management interface protocol; 4) GY / T145 broadcast TV SDH trunk network network element Management information model specification; 5) GY / Z174 digital television broadcasting service information (S1) specification; 6) GY / Z175 digital television broadcasting conditional access system (CA) specification.
(3) Studio parameter standards, as follows:
1) GB / T14857 studio digital TV coding parameter specification; 2) GB / T17953 4: 2: 2 digital component image signal interface; 3) GY / T155 high-definition TV program production and exchange video parameter values; 4) GY / T156 studio digital audio parameters; 5) GY / T157 studio high-definition TV digital video signal interface; 6) GY / T158 studio digital audio signal interface; 7) GY / T1594: 4: 4 digital component video signal Interface; 8) GY / T160 studio digital TV auxiliary data signal format; 9) GY / T-161 digital TV auxiliary data space transmission specifications in the auxiliary data space; 10) GY / T 162 high-definition television serial 24-bit digital audio format as ancillary data signals in the interface; 11) GY / T 163 digital TV ancillary data space time code and control code format; 12) GYB-164 studio serial digital optical fiber transmission system; 13) GB / T14919 digital sound signal source coding technical specifications; 14) GB / T14920 four-channel digital sound subcarrier system technical specifications; 15) GY / r 167 digital component studio synchronization reference signal; 16) GY / T 165 TV center broadcast Digital broadcasting channel of control system Technical indicators and measurement methods.
(4) Video coding and multiplexing standard 1) GB / T17975.2 Information technology-universal coding of moving images and accompanying audio signals; 2) Implementation guidelines for MPEG-2 video standard in digital (high-definition) television broadcasting (Consultation Draft); 3) Implementation Guidelines for MPEG-2 System Standards in Digital (High-Definition) Television Broadcasting (Consultation Draft).
(5) Channel coding and modulation standard 1) GB / T 17700-1999 satellite digital TV broadcasting channel coding and modulation standard; 2) GY hall 170-2001 cable digital TV broadcasting system channel coding and modulation specification; 3) GY / T143 cable Technical conditions and measurement methods for AM laser transmitters and receivers of TV systems; 4) General specifications for GY / T146 satellite digital TV uplink stations; 5) General technical requirements for GY / T147 satellite digital TV receiving stations; 6) GY / T148 satellite digital TV receiver technical requirements; 7) GY / T149 satellite digital TV receiving station measurement method-system measurement; 8) GY / T150 satellite digital TV receiving station measurement method-indoor unit measurement; 9) GY / T151 satellite digital TV reception Station measurement method ?? Outdoor unit measurement.
3. China Digital TV Development Plan In March 2005, the State Administration of Radio, Film and Television adjusted its development goals, and the new target was 10 million households. The transition plan is:
The first stage: By 2005, the cable TV in the municipalities directly under the Central Government, the cities above the prefecture (city) in the eastern region, the provincial capital cities in the central region, and some cities in the prefecture (city) \ part of the western region will complete the transition to digitalization.
The second stage: By 2008, the cable TV in cities in the eastern region and above counties, cities in the central region at the prefecture (city) level and most county-level cities, in some cities in the western region and above the county level and a few county-level cities have basically been completed. Digital transition.
The third stage: By 2010, cable TV in the county-level cities in the central region and most cities above the county level in the western region will basically complete the transition to digitalization.
Fourth stage: By 2015, cable TV in county-level cities in the western region will basically complete the transition to digitalization.
For the vast rural and remote areas in the west and areas that are not suitable for the development of cable TV, consideration can be given to the development of satellite reception.
Conclusion Development is the last word. 2006 is the first year of the “Eleventh Five-Year Plan”. The goal of achieving the digitalization of radio, film and television is the consensus formed by the radio and television industry during the fifteenth period. Important task. Opportunities, challenges, competition, and cooperation come together, and the integration between industries and networks has become a development trend.

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