High-definition digital TV transmission technology
There are four main transmission methods for HDTV signal transmission, through (live broadcast) satellite transmission, cable TV, terrestrial / mobile wireless digital TV network and IP network TV system, etc. Among them, for high-definition digital TV programs for national coverage, through (live broadcast) Satellite broadcasting is the most suitable solution. Correspondingly, they are called high-definition satellite digital TV, high-definition cable digital TV, high-definition terrestrial / mobile wireless digital TV, and IP high-definition network digital TV. among them:
1) High-definition digital TV transmitted through satellites For more than a decade, the European satellite digital TV transmission standard DVB-S (ETS 300 421) has been the standard for digital satellite transmission of MPEG-2 standard-definition video, and its data stream modulation Using four-phase phase shift keying modulation (QPSK) mode, the operating frequency is C band and Ku band (if it is a live broadcast satellite, its operating frequency is only in Ku band), and using MPEG-2 MP @ ML (main class @ ä¸»Grade) format, the user can achieve CCIR601 studio quality code rate of 9Mbps, and PAL quality code rate of 5Mbps. A 54MHz transponder can transmit up to 68Mbps, and can be multiplexed by multiple sets of SDTV programs. But as more video content shifts to high-definition formats, DVB-S has proven to be a transmission bottleneck in bandwidth allocation.
2) The high-definition digital TV transmitted through the cable TV network has a good foundation in China's cable digital TV. With the cable TV network as the transmission medium, its application range is wide and its development is also very fast. Its digital cable broadcast TV system uses the European standard DVB-C (ETS 300 429), which has 16QAM, 32QAM, 64QAM (corresponding to a maximum transmission bandwidth of 38Mbps), 128QAM (corresponding to a maximum transmission bandwidth of 44Mbps) and 256QAM (corresponding Maximum transmission bandwidth of 50Mbps) Quadrature amplitude modulation and other modulation methods.
3) The transmission capacity of terrestrial digital transmission of high-definition digital TV via terrestrial / mobile wireless transmission is roughly equivalent to that of cable TV system in theory, but it is limited by the permission of the wireless transmission frequency point; it can achieve better local wireless digital High coverage of TV. Due to the newer modulation method, 10 ~ 12 sets of standard-definition TV programs or at least 2 sets of high-definition TV programs can be transmitted within the 8MHz bandwidth, and the transmission cost is low.
4) HDTV digital TV transmitted through IP network system
IPTV, also known as interactive TV or broadband TV, is an access method that uses telecommunications and broadband Internet access (such as ADSL for telecommunications and Netcom, category 5 line in the community, etc.), or a new variety of TV programs transmitted via FTTH (fiber to the home). Interactive TV communication form; it integrates various technologies such as Internet, multimedia, and communication. It provides home users with a variety of interactive digital media services, including digital TV, through Internet protocol. Internet TV users can pass through at home Personal computers or "network set-top boxes + ordinary or high-definition TV" to receive all kinds of network TV programs, not only provide traditional video services and Internet browsing, but also develop new interactive services and support digital TV platforms , Enjoy interactive entertainment and services on an integrated network service platform, such as online transactions, interactive on-demand, TV voice mail, and online games, and because of its many channels and content, it can meet a large number of different levels of Internet TV users Demand.
To transmit high-definition digital TV programs in the IP network system, in addition to using real-time MPEG-2 / MPEG-4 / H.264 / AVS high-definition streaming media encoding equipment, it is also necessary to specifically ensure the transmission bandwidth of the IP network. Only the 5Mb / s broadband network connection and the corresponding IPTV high-definition digital TV receiver set-top box can watch HDTV high-definition digital TV programs in the IP network.
Satellite, cable, terrestrial and mobile wireless digital TV networks can use different modulation methods to transmit digital TV signals. The following table lists the various modulation methods currently or planned to be used according to different common transmission methods for reference. .
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