Source encoding is the process of bitrate compression of the encoding of original image or sound information. The source encoding needs to ensure that the receiving information source decoder can reconstruct the image or sound quality required for specific services.
At present, the main difference in digital television standards among different countries or regions is the transmission standards, especially the terrestrial transmission standards. Although the source coding standards vary in specific regulations, the vast majority of video coding follows the second part of the MPEG-2 standard (ISO/IEC13818-2, shared by ITU-T's H.262), and audio coding uses layer 2 of the third part of the MPEG-1 standard (ISO/IEC11172-3), Or Dolby AC-3 standard (A/52 in ATSC), or MPEG-2 AAC (ISO/IEC13818-7). The third part of the MPEG-2 standard (ISO/IEC13818-3) is compatible with the third part of MPEG-1 (ISO/IEC11172-3) and extends multi-channel encoding. The Chinese national standard GB/T17975.3-2002 "Information Technology - General Coding of Moving Images and Associated Sound Signals - Part 3: Audio" is compatible with it. The encoded audio and video streams, as well as other data streams, are multiplexed according to Part 1 of the MPEG-2 standard (ISO/IEC13818-1, shared by ITU-T's H.222.0, and also adopted by MPEG-4, H.264/AVC, and AVS). The progressiveness of MPEG-2 standard is relative. Driven by the demand for digital audio and video coding technology, ISO/IEC and ITU-T established the Joint Video Working Group (JVT) in 2001 and formed the final draft of the new standard in December 2002. This standard is referred to as H.264 in the ITU-T standard series, and is part 10 of MPEG-4 in the ISO/IEC standard series (ISO/IEC14496-10), also known as the Advanced Video Coding Standard (AVC). The video encoding standard of JVT is commonly referred to as H.264/AVC. H. 264/AVC introduces multiple complex and effective technologies to achieve good coding quality even at lower bit rates. Due to the division of video encoding layer (VCL) and network extraction layer (NAL) in H.264/AVC, in addition to high compression rate, it also has good network affinity. With the rapid development of digital signal processing and integrated circuit technology, the problems caused by the complexity of H.264/AVC algorithm will be relegated to a secondary position. Its higher compression efficiency and suitability for network transmission will become increasingly prominent, and its application prospects are very broad. For example, DirecTV's satellite live digital television business in the United States plans to adopt the H.264/AVC encoding standard, while the video encoding of DVB-S2 satellite digital television systems in Europe also prefers the H.264/AVC standard.
The video encoding of HDTV programs currently being piloted in China adopts the MPEG-2 standard, which is superior to its main category
（ MP@ML ）Correspondence. The maximum transmission rate of a satellite repeater or a cable TV frequency point is 38Mbit/s, and its net data rate can transmit 1 channel of HDTV plus 3 channels of SDTV, or 2 channels of HDTV programs.
In 2001, the State Administration of Film and Television of China formulated the industry standardization guidance technical document GU/Z-2001 "Digital Electricity
Visual Broadcasting Business Information Standards. Based on MPEG-2 Part 1, which is the national standard GB/T17975.1-2000 Part 1 PSI (Program Specific Information), and referring to the European telecommunications standard ETSIEN300468 (DVBSI), the specification specifies the service information for DTV broadcasting in China. The specification also specifies the encoding of Chinese characters, electronic program guides, original network identifiers, and network identifiers in DTV broadcasting business information in the appendix. This specification can also be used to develop basic EPGs. In terms of source coding, China's State Administration of Film and Television also formulated the industry standardization guidance technical document GY/Z175-2001 Specification for Digital Television Broadcasting Conditional access System in 2001. The Ministry of Information Industry has also proposed an industrial policy to promote the development of digital television terminals that separate machines and cards. To this end, the Ministry of Information Industry has issued SJ/T11336-2006 Digital TV Receiver Conditional access Interface Specification Part 1-1; DTV-CI Technical Specification and SJ/T11337-2006 Digital TV Receiver Conditional access Interface Specification Part 1-2: DTV-CI Test Specification. These two specifications involve the common interface (CI) for transmitting TS between the host and CA module, as well as the command interface and DTV-CI testing for communication between the two.
The various encoding streams, system management, and control information in China's digital television system are all in accordance with the first part of the MPEG-2 standard
Partial (ISO/IEC13818-1) multiplexing is equivalent to the Chinese national standard GB/T17975.1-2000 "Information Technology - General Coding of Moving Images and Associated Sound Information - Part 1: Systems".
In March 2006, the National Standardization Administration officially issued the video part of the AVS standard (AudioVideocoding Standard) GB/T20090-2006 "Advanced Audio and Video Coding in Information Technology - Part 2: Video", which was implemented on March 1, 2006. The AVS video encoding standard is based on innovative technology and some publicly available technologies in China, and has optimized the H.264/AVC video encoding technology to a certain extent. The efficiency is comparable to it and the quality is similar, but the technology is relatively simple. Currently, it is urgent to improve its industrial production capacity and provide high-quality and stable chips and complete machine products as soon as possible. AVS is a fundamental compression coding technology standard with independent intellectual property rights, and its adoption will have great significance in saving patent costs and reducing China's dependence on foreign key technologies.