According to experts, video telephony in the transmission channel can be divided into PSTN (public telephone network) type, ISDN (Integrated Services Digital Network) type, private network type and other ways. Video phones working on the PSTN can transmit 10-15 frames per second; Video phones working on ISDN can transmit more than 15 frames per second. At present, there are two main types of video phone products, one is the personal computer as the core of the video phone, in addition to the computer is also equipped with a camera (or small camera), microphone and speaker input and output equipment; The other type is dedicated video telephone equipment (such as body video telephone), which can be directly connected to the home telephone line for video calls like ordinary phones. Because of the high penetration rate of ordinary telephone lines, video telephony working on the public telephone network has the greatest potential for development.

        In recent years, video telephony has developed rapidly in developed countries. With the publication of ITU-IH.324, the international standard for PSTN multimedia video telephony of the International Telecommunication Union in 1996, video telephony in line with the standard has been developed in the United States, Japan, Germany and soon entered the household. Although it is difficult to popularize video telephony in China due to various factors, the use rate of video telephony in some government departments, enterprises and groups is gradually increasing. Relatively inexpensive video phones are also being developed. At present, China's South China photoelectric instrument Factory, Shenzhen Yaxiang Industry and Trade Development Co., LTD. (in cooperation with Taiwan Xinghe Electronics Co., LTD.), Shandong Keling Electronic System Co., Ltd. have new video phone products on the market. These new products are using advanced digital compression and decompression technology, in line with the ITU-TH.324 standard, the use of the most extensive coverage of the PSTN (public telephone network) as the carrier, just connect the video telephone with the ordinary telephone line and power on, you can easily make video calls, display their own and each other's dynamic images on the screen, Let the two parties fully enjoy the feeling of being in the scene, and the call fee is the same as the ordinary phone.

Video communication standard:SIP 2.0

Video coding standard:H.263

Audio coding standard:G.711au, G.723, G.726, G.729, iLBC, AMR, CN, Telephone-Event