【 Weak current College 】 video conference system related key technologies which» ---Power By 【 China power house network 】

(1) video encoding technology source compression is always the communication area of one of the core technology. For video business, compression technology is particularly important because of the video signal is a large amount of data, a standard PAL signal rate 216Mbit/s. If you do not compress basically impossible transmission, compression to 2Mbit/s can only be transmitted over a communication route, cannot be extended to the end user. Hence the need to improve the compression efficiency, on the one hand, through the image quality of degraded matter, but mainly improves coding efficiency. MPEG2 is mainly used for relatively high bit-rate video coding, for very low bit rate video coding, you should use the appropriate compression standard, the main compression standard is the ISO ITU-T H.263 and MPEG4 standard. H.263 + can accommodate high BER communication network. H.263 + standards, based on the H.263 on coding method to do a lot of improvements and the option form exists. In improved options taking into account the coding efficiency, also taking into account the increased channel fault tolerance. H.263 + and H.263 video quality in the same case, the transfer rate is only 50%. H.263 + has gradually become one of the new technology. (2) voice coding technology meets the G.711, G.729, G., G.728, G.723.1 standard speech codec. The standard rate is decreasing, each terminal is generally not possible to have met all of these standards, decoding, and the beginning of the meeting, you can select a shared with decoding standards, when the same standard for more than one time, then press the pre-set priorities. Voice quality, occupies the frequency bands are usually guaranteed. But the meeting system with voice start priority when voice of orientation and intensity for accurate recognition. (3) network protocols and system control in the video conferencing system and all information is transmitted through a communications network, so the need to establish, through the call process, such as a physical channel H.225.0 Q.931, etc, to make data transfer. User data including video, audio, data and other information for each type of information can only occupy a single logical child channels. So you will need to make the child channel multiplexing multiplexer/solutions. Think more user participation, so that bandwidth control, access control, etc. Need a rational allocation of resources, ensure the system's stability. (4) the quality assurance system (QoS) because there is no IP networks, QoS guarantee based on the H.323 protocol for video conferencing system, you need to do QoS treatment. Currently, QoS is not very mature, become more active on the new area. For a network, the end-to-end QoS is key. QoS includes a series of mechanisms that allow network administrators to control the network bandwidth, latency, variation (jitter) and packet loss, etc., in order to provide as such a business VoIP, or as a different user, different application definition, the different service-level agreements (SLA) over a WAN routing different priority business. Because implementation of QoS is a network-level solution, you need to end-to-end. Therefore an effective QoS solutions must not depend on the implementation of the object, that is not dependent on the operating platforms, network equipment and transmission media, etc., it must be running on the IP layer or IP layer above, cover a variety of network equipment and a variety of link road to ensure end-to-end QoS functionality. For example Cisco company in all network devices support QoS software and technology that are equipped with a complete set of QoS implementation tools, these tools allow network managers from the network core to the edge of the implementation of the unified network QoS assurance mechanism.