The Development and Standards of Digital Television

The Development and Standards of Digital Television

I. What is digital television?
1. The concept of digital television Digital television refers to a new television system that uses digital television signals or processes and modulates digital television signals in all links from the studio to the transmission, transmission, and reception. All signal transmissions in this system are transmitted through a digital stream composed of a string of 0s and 1s. The transmission rate of digital signals can reach 19.39M bytes per second. Such a large data stream ensures the high definition of digital television and overcomes the inherent shortcomings of analog television. 2. Two mainstream explanations of digital television (1) In the 1980s, ITT developed a set of digital processing chips. When receiving analog television signals, they were processed by analog high and medium frequency, and finally converted into digital signals through analog/digital conversion for digital processing to improve image clarity. In the 1990s, a variety of "digital televisions" with picture-in-picture, multiple lines, and other improvements appeared. However, these televisions still received analog television signals and were not true digital televisions. (2) The "digital television" (abbreviated as DTV) in the United States refers specifically to terrestrial digital television broadcasting systems. In this system, except for the part of the current program production that is still analog, all links from the studio to the transmission, transmission, and reception use digital TV signals. Therefore, only this type of TV is truly a digital TV. 3. Advantages of digital TV Digitalization is a technological transformation of the radio and television industry, which will bring about a revolution in radio and television. The digitization of cable TV mainly brings about changes in three aspects: (1) Quantitative changes. Now we can watch 30 to 50 TV programs through cable TV networks. After digitization, we can watch hundreds of TV programs. (2) Qualitative changes. After digitization, our TVs have become multimedia information terminals. Not only can we watch TV programs, but we can also listen to the radio, obtain a variety of information services, and use TV shopping and pay water and electricity bills. It has become an indispensable tool in people's lives and a supporting platform for the modern service industry in society. (3) Changes in methods. Now we watch TV passively. After digitization, we can actively watch and choose the programs we like according to our own time. It can be said that the digitization of radio and television 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, signal damage caused by sampling process, quantization error, compression coding, and through delay in program production and transmission. Some damage can be repaired and does not affect the final quality of the image, while some damage can only be weakened by some compensation measures, but this cannot affect the transformation of the television field to digitalization.
5. Classification of digital TV
● According to the signal transmission method, it can be divided into: terrestrial wireless transmission digital TV; satellite transmission digital TV; cable transmission digital TV. ● According to the image clarity, it can be divided into three categories: digital high-definition television (HDTV); digital standard definition television (SDTV); digital ordinary definition television (LDTV). ● According to the product type, it can be divided into: digital TV display, digital TV set-top box and integrated digital TV receiver. ● According to the display screen aspect ratio classification: digital TV can be divided into two types of 4:3 and 16:9 aspect ratio.

2. Digital TV Standards
In the digital TV transmission code stream, there are clear regulations on how big a data packet is, how many bytes it contains, what each byte means, and even what a certain bit of a byte means. This is the standard. There are currently three types in use: ATSC (Advanced Television Systems Committee) in the United States; DVB (Digital Video Broadcasting) in Europe; ISDB (Integrated Service Digital Broadcasting) in Japan.
Each digital TV standard can be divided into satellite transmission, cable transmission and terrestrial transmission methods.
1. ATSC Standard in the United States
The ATSC digital TV standard consists of four separate layers with clear interfaces between the layers. 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 adopts the MPEG-2 image compression standard. The third layer is the system multiplexing layer, where specific data is included in different compression packets, such as program 1 image, program 2 sound, or auxiliary data, using the MPEG-2 system standard. The last layer is the transport 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 broadcast channel. The standard also includes the 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 the transmission of ordinary data, and the upper two layers determine the specific configurations that run on the basis of ordinary data transmission, such as HDTV or SDTV (standard definition television). The upper two layers also determine the specific image formats supported by the ATSC standard. There are 18 formats (6 for HDTV and 12 for SDTV), 14 of which use progressive scanning.
(1) HDTV, 1920 pixels (H) x 1080 pixels (V), aspect ratio 16:9, frame rate 60Hz/interlaced scanning, frame rate 30Hz and 24Hz/progressive scanning;
(2) HDTV, 1280. Pixels (H) x 720 pixels (V), aspect ratio 16:9, frame rate 60Hz, 30Hz, 24Hz/progressive scanning;
(3) SDTV, 704 pixels (H) x 480 pixels (V), aspect ratio 16:9 or 4:3, frame rate 60Hz/interlaced scanning, frame rate 60Hz, 30Hz, 24Hz/progressive scanning;
(4) SDTV, 640 pixels (H) x 480 pixels (V), aspect ratio 4:3, frame rate 60Hz/interlaced scanning, frame rate 60Hz, 30Hz, 24Hz/progressive scanning.
Except for one type, all HDTV image formats use progressive scanning. Because the 1920x1080 format is not suitable for progressive scanning at 60 frames/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 computers to ensure compatibility with computers. Among all 12 SDTV formats, 9 use progressive scanning, and 3 are reserved for interlaced
scanning to adapt to existing video systems.
In addition, ATSC has also developed and passed a separate standard for use in countries with a frame rate of 50Hz. The pixel array of HDTV is the same, but the frame rate is 25Hz and 50Hzo SDTV format has a vertical resolution of 576 lines and a different horizontal resolution; it also includes a 352x288 format to adapt to the necessary window settings. The ATSCDTV standard based on the 50Hz version makes it easier to use in countries with a frame rate of 50Hz.
ATSC has 30 members, and China's Broadcasting Science Research Institute has also participated in the ATSC organization.
2. European DVB Standard DVB standard includes: DVB broadcast transmission system, DVB baseband additional information system, DVB interactive service system, DVB conditional reception and interface standards. The details are as follows: (1) DVB broadcast transmission system The DVB digital broadcast transmission system utilizes all common television broadcast transmission media including satellite, cable, terrestrial, SMATV, and MNDSD. They correspond to the following DVB standards: DVB-S, DVB-C, DVB-T, DVB-SMATV, DVB-MS, and DVB-MC. 1) DVB-S (ETS 300421) - Digital satellite live broadcast system standard. This standard uses satellite 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 the output signal can be received by the existing analog TV. The modulation of the data stream adopts the quadrature phase shift keying modulation (QPSK) method, and the operating frequency is 112GHz. When using the MP@ML (Main Profile@Main Level) format of MPEG-2, the user end achieves a bit rate of 9Mb/s for CCIR601 studio quality and a bit rate of 5Mb/s for PAL quality. A 54MHz transponder can transmit at a rate of up to 68Mb/s and can be used for multiplexing of multiple programs. After the DVB-S standard was announced, almost all satellite live digital televisions adopted this standard, and China also chose the DVB-S standard. 2) DVB-C (ETS 300 429) - Digital cable broadcasting system standard. This standard has three modes: 16, 32, and 64QAM, and the operating frequency is below 10GHz. When using 64QAM orthogonal amplitude modulation, the transmission rate of a PAL channel is 47.34Mb/s, and it can also be used for multiplexing of multiple programs. The industry standard "Cable Digital Television Broadcasting Channel Coding and Modulation Specifications" promulgated by the State Administration of Radio, Film and Television in 2001 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, the coded orthogonal frequency division multiplexing (COFDM) modulation method is used, and 4 sets of TV programs can be transmitted within an 8MHz bandwidth, with high transmission quality and fewer channels. 4) DVB-SMATV (ETS 300 473)??Digital SMA'IV (satellite master antenna television) broadcasting system standard. 5) DVB-MS (ETS 300 748)?--Digital broadcast MMDS distribution system standard above 10GHz. MMDS is a system that uses amplitude modulated microwaves to transmit to multiple points and distribute multi-channel TV programs. This standard is based on DVB-S, allowing microwave signals carrying a large number of programs to enter the home directly. A DVB-S receiver equipped with an MMDS frequency converter can receive DVB-MS signals. 6) DVB?MC (ETS 300 749)??Digital broadcast MMDS distribution system standard below 10GHz This standard is based on DVB-C, allowing microwave signals carrying a large number of programs to enter the home directly. A DVB-C receiver equipped with an MMDS frequency converter can receive DVB-MC signals.

(2) DVB baseband additional information system In addition to transmitting ordinary video and audio signals, the DVB digital broadcasting system also needs to transmit and receive old D tuning, program guides, as well as graphics, subtitles, icons and other information. 1) DVB-S1 (ETS 300.468)??Digital broadcasting service information system standard. This standard consists of a series of tables and descriptors, which give all parameters related to DVB services or programs. 2) DVB-TXI (ETS 300 472)??Digital teletext broadcasting system standard. This standard is used for the transmission of fixed-format teletext television. 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) DVB interactive service system Based on the general DVB digital broadcasting system, the elements that further constitute the interactive service system include an interactive service network independent protocol compatible with other relevant international standards, a return channel for transmitting interactive service process command and control signals, etc. 1) DVB-N, P (ETS 300 802) / DVB interactive service network independent protocol standard. 2) DVB?RCC (ETS 300 800) -- CALX / system DVB return channel standard. 3) DVB?RCT (ETS 300 801) -- PSTN / ISDN DVB return channel standard. (4) DVB conditional access and interface standards Some services in the DVB digital broadcasting system transmit scrambled conditional access information. The common interface of conditional access enables IRD (integrated decoding receiver) to descramble the scrambled information using a common 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 DVB technology, and its interface with these telecommunication networks realizes the transition of DVB to telecommunication networks. In addition, there are interfaces for connecting professional equipment and old D. 1) DVB-CI (EN 50221) - General interface standard for conditional access and other applications . 2) DVB-PDH (ETS 300 813) - DVB interface standard for PDH (quasi-synchronous digital hierarchy) network. 3) DVB-SDH (ETS 300 814) - DVB interface standard for SDH (synchronous digital hierarchy) network. 4) DVB-ATM (ETS 300 815) - DVB interface standard for ATM network. 5) DVB-PI (EN 50083-9) - CA-IV/SMAIV front-end and similar professional equipment interface standard. 6) DVB-IPDI (EN 50201) - DVB-IRD interface standard. DVB members have reached 265, including China's Broadcasting Science Research Institute and TCL Electronics Group. 3. ISDB is a digital broadcasting system standard developed by DIBEG (Digital Broadcasting Experts Group) in Japan. It uses a standardized multiplexing scheme to send various types of signals on a common transmission channel, and the multiplexed signals can also be sent through various transmission channels. It can be predicted that in the near future, digital television standards such as ATSC, DVB, and ISDB will no longer exist, and will be replaced by a unified international digital television standard.

3. China's Digital Television 1. Development of China's Digital Television Since the Ministry of Science and Technology approved the implementation of China's major high-definition television science and technology industry project in 1995, China's digital television has experienced ten years of development and has achieved remarkable results. Since 2000, the state has established a special project for digital television research and development and industrialization, focusing on the research and formulation of national digital television standards with independent intellectual property rights, digital television industrialization and application promotion experiments, including the approval of three experimental areas and two testing laboratories in Beijing, Shanghai and Shenzhen, and the approval of a series of industrialization development projects. The digital television development plan was included in the list of 12 major projects of the "15th Five-Year Plan" high-tech, and the research work on digital television was fully launched. 2. China's Digital Television Standards At present, the standards related to digital television issued in China are as follows: (1) Digital (high-definition) television standard system. (2) Basic standards for digital television, as follows: 1) GB/T7400.11 Digital television terminology; 2) GY/T134 Subjective evaluation method for digital television image quality; 3) GY/T144 Broadcasting and television SDH backbone network management interface protocol; 4) GY/T145 Broadcasting and television SDH backbone 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 television coding parameter specifications; 2) GB/T17953 4:2:2 digital component image signal interface; 3) GY/T155 Video parameter values ​​for high-definition television program production and exchange; 4) GY/T156 Studio digital audio parameters; 5) GY/T157 Studio high-definition television 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 television auxiliary data signal format; 9) GY/T-161 Transmission specification for digital audio and auxiliary data in digital television auxiliary data space; 10) GY/T 162 24-bit digital audio format as auxiliary data signal in high-definition television serial interface; 11) GY/T 163 Format of time code and control code in digital television auxiliary data space; 12) GYB-164 Studio serial digital optical fiber transmission system; 13) GB/T14919 Technical specification for source coding of digital sound signals; 14) GB/T14920 Technical specification for four-channel digital sound subcarrier system; 15) GY/R 167 Synchronization reference signal for digital component studio; 16) GY/T 165 Technical indicators and measurement methods for digital broadcast channel of TV center broadcast control system. (4) Video coding and multiplexing standards 1) GB/T17975.2 Information technology - general coding of moving images and their accompanying audio signals; 2) Implementation guidelines of MPEG-2 video standard in digital (high-definition) television broadcasting (draft for comments); 3) Implementation guidelines of MPEG-2 system standard in digital (high-definition) television broadcasting (draft for comments). (5) Channel coding and modulation standards 1) GB/T 17700-1999 Satellite digital TV broadcast channel coding and modulation standards; 2) GY/T170-2001 Cable digital TV broadcast system channel coding and modulation specifications; 3) GY/T143 Cable TV system AM laser transmitter and receiver network access technical conditions and measurement methods; 4) GY/T146 Satellite digital TV uplink station general specifications; 5) GY/T147 Satellite digital TV receiving station general technical requirements; 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 receiving station measurement method - outdoor unit measurement. 3. China's digital TV development plan In March 2005, the State Administration of Radio, Film and Television adjusted the development target, and the new target was 10 million households. The transition plan is as follows: Phase I: By 2005, the cable television in municipalities, cities above prefecture level in the eastern region, provincial capitals and some prefecture level cities in the central region, and some provincial capitals in the western region will have completed the transition to digitalization. Phase II: By 2008, the cable television in cities above county level in the eastern region, cities above prefecture level and most county level cities in the central region, and some cities above prefecture level and a few county level cities in the western region will have basically completed the transition to digitalization. Phase III: By 2010, the cable television in county level cities in the central region and most cities above county level in the western region will have basically completed the transition to digitalization. Phase IV: By 2015, the cable television in county level cities in the western region will have basically completed 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 television, it is possible to consider developing satellite reception. Conclusion Development is a hard truth. 2006 is the first year of the "Eleventh Five-Year Plan". The development goal of achieving the digitalization of radio, film and television is the consensus formed by the radio and television industry during the Tenth Five-Year Plan. Promoting the digitalization of radio and television is an important task for radio and television people during the "Eleventh Five-Year Plan". Opportunities, challenges, competition and cooperation arise together, and the integration between industries and networks has become a development trend.