Before the Beijing Olympic Games, terrestrial digital TV was launched, using DMB-H scheme, MPEG-2 and H.264 for video coding and ACC and MP3 for audio coding, all of which are international common standards. And from the beginning, the mode of encrypted charging was adopted. This scheme introduces HD mode for home TV (only in a few cities such as Beijing) and CMMB mode for mobile devices respectively. Due to the cost and patents, it has not been widely promoted nationwide. Only CMMB has formed a certain market because it is used for rural household registration.
Shortly thereafter, China began to formulate its own terrestrial digital TV standard DTMB. Video coding adopts AVS+ (AVS is incompatible in the early stage), and audio coding adopts DRA, which is played by Liu Qing for free. It has become a new national standard for terrestrial digital TV, and has been listed as one of the four global standards by ITU.
DTMB terrestrial digital TV has been piloted in Hunan since 20 13. In 20 14, it is required that the newly listed TV sets of 40 inches and above must directly support the reception and decoding of this standard, that is to say, ordinary terrestrial wave antennas can watch directly without set-top boxes. However, there are still a large number of TV sets on the market that do not support the audio and video decoding of the new national standard and need external ground wave set-top boxes.
At the same time, the original CMMB terrestrial digital TV signal is still broadcasting, and the DTMB terrestrial digital TV transmission towers in many places have just started construction and have not been put into use, so some places can only find encrypted terrestrial wave channels to charge DTMB. In addition, it is not excluded that some TV manufacturers that focus on network TV function deliberately block DTMB signals.