Video-telephony

Video-telephony is to use telephone line the speech of the real-time transmission and images (user of bust, photos and articles, etc.) of a kind of communication mode. If the ordinary telephone is "ears", then the videophone will both "ears", and "forward".

equipment

Video-telephony is by telephone, camera equipment, TV receiving display equipment and controller to compose. The videophone phone and ordinary as a telephone is used for conversation, Camera equipment function, is to get his user image transmitted to the other, TV receiving display device, its effect is receiving each other's image signal and on the screen shows each other's image.

Section classification

The image shows the videophone according to different, divided into static images videophone and dynamic image videophone. Static images videophone on fluorescent screen displayed image is static, image signal and voice signal utilization of existing analog telephone system, namely transfer image transmit alternately can call, Transmit a frame of users bust still images need 5-10 seconds.

application

A videophone equipment can be like an ordinary as a telephone access PSTN use. Dynamic image videophone displayed image is active, users can see each other's smile or talk image. Dynamic image videophone image signal for contains large amount of information, accounts for the wide frequency band, not directly in users online transmission, needing the original image signals into digital, digital image signal, and then must still using band compression techniques of digital image signal, "compression", make the accounts for the band, so that it can narrow in users online transmission. Dynamic image videophone signal for digital signals, so be on both digital transmission. The videophone can also add video recording equipment, like recording telephone same, the image recording down in order to preserve. Static images videophone already in public phone use online, and the dynamic image videophone because of high cost of application has not yet. But can be expected, as microelectronics technology development, the large-scale, vlsi, as well as the extensive use of the rapid development of integrated services digital network, dynamic image videophone inevitably in the future communication plays an important role.

The videophone business

The videophone business is a point-to-point of video communication business, it can use telephone network two-way real-time transmission call both images and the speech signal. Because the videophone can get face-to-face communication effect, realizing people communication both hear its voice, and see its person dreams, so since the idea after suffer the widespread acclaim for her, and people were expected to do that. However, after a long wait for the videophone has not been widely used, always from ordinary users far away. Video-telephony is just a hype? If not, then the videophone development condition? Market foreground how?

Bumpy decades

The videophone from concept put forward, technical development to market startup, after many bumps and tortuous. Especially in China, videophone market in the long run, thunder, roast situation, market delayed startup. Few customers have terminal after decades of research and development remain basically stay on books, fail to win, and large scale application videophone just at this unfortunate ranks.

As early as in a 1950s had been suggested videophone concept, that should use telephone line transmit speech simultaneously transmit images. In 1964, the United States bell LABS officially proposed videophone related solutions. But, as the traditional network and communication technology, the constraint of videophone hasn't been substantial progress. Until the late 1980s, with the chip technology, transmission technology, digital communications, video decoding technology and integrated circuit technology unceasing development and matures, suitable for commercial and residential videophone was able to come to the surface to people's perspective.

Decoding chip technology is the key to the development of video-telephony, without a core decoding chips, videophone is only like, non-existent. Voice and image in transmission, must pass a compression - decoding process, and the chip is undertaking the task of coding and decoding, only chip on the output side will voice and image compression and compiled into the suitable for transmission lines of communication in a special code, but in the receiver will be special code into people can understand the voice and image, can form a complete transmission process, make conversation with both realize sings in the exchange.

Transmission line influence videophone communications quality. The traditional telephone lines were ordinary twisted-pair cable, used primarily to transmission of voice, audio simultaneous transmission, the transmission rate can only reached 3.36 K, so in ordinary telephone lines, under the support of cannot transmit clear coherent image.

Protocol standards are inconsistent, affect the market promotion. Long-term since, although there are makers offer videophone, but because they fragmented, and does not have uniform standard, and various videophone not share, affecting the videophone market development. In the protocol standards not unified case, only the users buy the same type of videophone to achieve "visible" effect, if a user bought a manufacturer of visible calls, and b users buy is b home, then they call can't "visible".