Position:The multimedia communication that video conference is a kind of model uses example. 60 time developed country begins to have the research of video conference, inchoate video conference system is transmitted with imitate means, take up very big bandwidth, the 1MHz bandwidth of company of BT of the picturephone that its representing has lab of American shellfish Er to develop, England is black and white video conference system. At the beginning of 80 time end, 90 time, as signal of microelectronics, computer, number processing and image handle technical development, the academic research of video conference and respect of economic system development also got developing quickly. In general, the digital video conference that its developed to basically experience imitate video conference, digital video conference and international to unite a standard 3 phase.
60 time only then, world developed country begins to study system of imitate video conference, and gradually business is used change.
60 time evening, in compress encode technology to drive below, change a number to the system by imitate system.
80 time are prime, development gives system of conference of video of 2Mbps color number, japan and United States form network of nonstandard domestic video conference.
80 time metaphase, technology of circuit of large scale integration develops at full speed, image makes up decipher technology to obtain a breakthrough, channel charge is reduced, move toward for video conference practical offerred good development condition.
80 time end up to now, change quickly of multimedia technology, computer technology, communication network technology. CCITT (namely present ITU-T) formed H.200 series proposal, stipulated unified video inputs the output level, algorithmic standard, mode that piles up desired result standard to reach a series of each other to connect by accident to change a standard, the equipment each other that solved different manufacturer understands a problem, promoted the development of video conference greatly.
Since 90 time metaphase, the computer interrelates the flying progress of the net produced tremendous and profound effect to telegraphic course of study. The multimedia communication system that is based on packet of exchange network makes one of central points of researcher and attention of telegraphic, network and computer firm gradually. Group of Internet project assignment (IETF) also develop a real time to transmit an agreement (RTP) , resource obligate agreement (RSVP) wait to suggest to cooperate with the H.323 of ITU-T, in order to make sure video of frequency of deferent on IP network real time flows.
In light of the history that develops from video conference technology, current, of video conference system it is OK to build the H.323 of proposal of two big frame of basis ITU-T and H.320 will undertake, form two kinds of different construction plan thereby. H.320 is the video conference standard with more inchoate ITU-T, this standard is built completely on technologies of a series of video conference proprietary and standard, and H.323 standard is built in general, open computer network corresponds over technical base, have wide development perspective. Since since ITU-T approved this standard 1996, the technology of video conference and market produced revolutionary change. More and more manufacturer throw the development of H.323 new product eagerly, more and more users use the video conference system of H.323 technology and product construction themselves. This is the inevitable trend that communication network technology, computer technology and multimedia technology develop at full speed and increasingly shirt-sleeve place brings. And, the H.323 system convenience in advanced sex of the technology, perfect sex of the function, operation of gender, system but expanding and each respect such as performance/price ratio, show clearer than H.320 system advantage increasingly.
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