【 Weak current College 】 multimedia video technology development---Power By 【 China power house network 】

Multimedia video conference and video conference, video conference, etc, it can be implemented in two-point and multi-point real-time shipping activity image, voice, and application data (electronic white boards, graphics), and other forms of information. First, based on circuit-switched network video conferencing in the 1970s, many countries meeting TV pilot, but are basically using simulation mode to transfer images, not only makes operation costs, while also making a lot of people during the Conference will not be able to use voice circuit intercom; during the 1980s, the meeting was basically TV business digital transmission methods. Since the meeting of the TV and in many cases for multipoint communication, problem solving interoperability is critical. ITU-T (formerly CCITT) in 1984 to develop a H.120 and H.130, unifies data compression algorithm, and then in November 1990, adopted the new recommendation H.261 and H.200 series, solved H.120 and H.130, outstanding standard TV format, PCM. These recommendations, and is used to transfer still images of the T.120, ultimately forming a H.320 series standard, an important part. H.320 ISDN series standards support, E1 and T1 bandwidth from 64 ~ 2Mbit/s. The proposed specification a ISDN network video conferencing system the main technical aspects, this is the first formulation based on specific network protocols for video conferencing business interchange between different products as well as the Internet provides basic protection, this standard was introduced at the Conference in the history of the significance of the milestone, as video conference development and universal access. The main components of equipment H.320 have multipoint control unit (MCU) and terminal equipment. This was a very comprehensive system, but because the system is based on circuit-switched networks, are a lot of restrictions, also leads to many problems. Circuit switching characteristic is connection-oriented, transfer rate and delay of stable, low-delay is small, the error rate, and therefore the quality of the video conference to be guaranteed. But the disadvantage is fixed, causing the user line use high cost. User level access generally use El green mode or ISDN2B + D access mode connections, leased lines while guaranteeing good stability and image quality, but the network utilization is low. ISDN greater impact by line, for line synchronization requirements. Both transport mode limits the size of the meeting and scalability, practical networking network size is difficult to conduct further expansion. Second, based on the IP network video conferencing with packet switching technology, ATM in one stage in a big way. Since 1995, has been launched ITU-T for ATM networks H.310 and H.321 series standards. But over time, the possibility of the ATM to the desktop, and application of H.310 or H.321 possibility is also very small. In 1996, ITU-T introduced for computer LAN H.322 and H.323 series standards. H.323 standards after four years of development, its 2000 launch of the Fourth Edition was most manufacturers support the Conference. H.323 is not a single standard, but rather one concerning IP environment full of real-time multimedia applications, it is the standard calls for the establishment, management, as well as the transmission media formats, and so has a complete and strict rules. IP-based H.323 standard can make full use of network resources and their constituent elements including video Terminal, multipoint control unit, gateway and gateway, you can add video to the Office desktop, use data real-time interactivity, complete coordination office, enables users to fundamentally out of the meeting must go to the fixed limit, the realization of the Conference room in the true sense of the video communication and supports manufacturers equipment, interoperability. H.323 related to terminal equipment, video, audio, and data transmission, communication, control, network interface, also includes a composition more Conference multipoint control unit (MCU) (by multipoint controller (MC) and multi-point processor (MP)), gateway and gateway, etc. H.323 system is essentially a balance between the traditional PSTN call flow and IP network features and development of open standards system, which represents the great Telecom multimedia services. Its success is to draw a number of telecommunication networks of networking, Internet and operational experience, and PSTN networks, and narrowband video business, and other data services and applications of network interconnection. Use H.323 networks can develop many of the underlying network transport-independent multimedia applications such as multimedia and video conferencing, multimedia, monitoring, multimedia production dispatching, remote corporate training and education, multimedia call center, IP telephony, Internet online IP fax, online video and broadcasting, and you can use H.323 applications and business will be accumulated to the same transport network platform. H.323 with Advanced TCP/IP technology, provide the same performance and functionality at the same time, significantly reducing the cost of user terminal and subscriber line use costs, with high performance-price ratio. Third, multimedia video technology development 1.H.264 coding and H.264 encoding technology is H.239 by ITU-T and ISO/IEC MPEG joint establishment of the expert group "joint video team" joint development of new recommendation (ITU-T H.264). It is a classic of the basic framework of mixed encoding on the MPEG-4 video encoding algorithm strengths, it has a high coding efficiency: than H.263 encoder saves 50% of the bit rate; strengthen the limitations and the delay on the error and to color handling, enhanced decode error recovery capabilities; improve the adaptability of the network (such as mobile and IP networks adaptive), the use of layered technologies, from the form will be encoded and channel separation, in the source encoding process to consider the characteristics of the channel.
The main contents of the H.239 is on in the video conference system using multiple video channels, define role identity to achieve control, direction and capacity to exchange mechanism. 2. mobile video 90 years of the 20th centuryGeneration towards the rapid development of mobile communications begin. With 3 g technology for perfect, in the mobile Internet has launched video communication service may, in this context, the H.324M standard has gradually come to the foreground. Currently, Japan's DoCoMo has established H.324M video communication network, and traditional H.320 and H.323 networks enables interoperability. H.324M standard refers to the standard of "mobile H.324 part" extension. H.324 protocol specifies how to use the synchronously V.34 Modem to be based on the POTS (Plain Old Telephone Systems) of multimedia communication. In order to extend the wireless or mobile industry standards, the mobile extension (H.324M) in H.324 annex C and H.223 annexes a, B, c are made separately defined. 3GPP adopted recommendations as a 3 g network H.324M traditional video phone is a standard, its adoption of recommendations is named 3G-324M, and for voice, video and multiplexing operations made a number of requirements: requires GSM-AMR become audio coding one of the optional encoding standards; mandatory ITU H.263 for video coding standards; add H.223 annex B used to protect data. 3. the Conference based on SIP SIP (Session Initiation Protocol, Session Initiation Protocol) is determined by the IETF (Interne Engineering Task Force) in 1999 to IP telephony signaling protocol. It is used to initiate the session, can control multiple participants of multimedia session establishment and termination, and can dynamically adjust and modify the session properties such as session bandwidth requirements, transfer of media types (voice, video and data, etc.), media codec format, multicast and unicast support, etc. H.323 and SIP, H.323, the existing traditional realization telephone signaling mode, more mature, there is a lot of H.323 products. H.323 compatible with traditional design in the field of communications, for centralized, hierarchical control, using the H.323 protocol for connecting with the traditional telephone network. SIP draws on other Internet standards and protocols for design ideas, follow the style of the Internet has consistently adhered to simplicity, openness, compatible and scalable principle, relatively simple, but its launch time, agreement is not very mature. 4. China Unicom broadband video conference network and business introduction 1. China Unicom broadband video network overview China Unicom broadband video services network is based on China Unicom ATM integrated business hosting platform, the use of advanced IP technology, H.323 and multi-stage GK network to provide users with the video and its value-added services of network platforms, China Unicom broadband video service is China Unicom broadband video based on Unicom network to provide users with simultaneous transmission of voice, video, and graphic information of a new business. Video Terminal on the users desktop or a public place, the user can line or broadband Internet access to China Unicom broadband video network with the business. China Unicom broadband video network covering more than 300 cities in Hong Kong, Taiwan, mastery, United States, Singapore, Australia and other countries and regions. The network currently online capacity 20 000 households, more Exchange capacity of 3500 384k port while supporting multi-party conference held 600, the maximum number of individual meetings of the parties may reach 300 party, pre fufeika capacity up to 500 000, traffic-carrying capacity up to 1 million minutes/month. China Unicom broadband video network offers the user to the Enterprise Conference room and desktop video conferencing services, while at the same time to have broadband Internet access conditions to provide services for home users. 2. China Unicom broadband video business classification (1) Enterprise broadband video service that is in place for enterprise branch offices in all parts of the video communication terminal, via Unicom data dedicated line or broadband Internet (broadband network cable or ADSL) access Unicom broadband video network, thus contributing to the formation of internal video network enterprises. (2) residential broadband video service that is in the users home placement video Terminal, through broadband Internet (broadband network cable or ADSL) access Unicom broadband video network, thus providing home users broadband video service. (3) public video phone business at Unicom public broadband video service sites placement video Terminal, in a public place for users with broadband video service. (4) broadband video conference room rental business is through cooperation with the hotel, at the national level within the user provides broadband video conference room rental service, users can convene national and world hotels within the scope of the Conference. 3. China Unicom broadband video service features (1) easy to use video phone calls between video Terminal, and just as easily as using mobile phone. Video Terminal room multiparty videoconferencing very friendly user interface, users only need to use a regular PC logon Web page, you can in your own Office or your own company's room very easily independent convening and conducting conferences control. (2) quality is outstanding Unicom broadband video network through ATM (QoS) + IP (flexible), the combination of the flexibility to operate at the same time, a solution to the traditional IP network cannot guarantee the quality, jitter, packet loss, and other parameters that can meet user's requirements. From a Visual perspective, sound quality continuous clear, image mosaic, active images continuously. At the same time, the unity of the whole network for equipment selection and whole network design, using international advanced equipment, the master device and the world's major carriers, compatibility, and therefore has good interoperability, can provide high-quality province, inter-provincial and international video services. (3) cost savings on enterprise users, and to organize videoconference network than Unicom broadband video service does not need to invest in the acquisition of MCU switching equipment, no need to MCU, Conference TV host network for maintenance, no need to invest in network upgrade, greatly saves costs. At the same time, China Unicom broadband video network system based on the H.323 technology, in an access point can easily achieve more than one video terminal access, easy expansion and reduce equipment investment. And other operators of video business compared to China Unicom broadband video service can provide the user with more favourable tariff. 4China Unicom broadband video service product features (1) peer to peer video conferencing, video phone is mainly used in Visual communication, through an ad-hoc terminal directly call the other number to establish communication, ideal for small meetings, visits, discussions, remotely, remote medical applications, etc. Users make use of meeting room-type terminal or desktop Terminal of the remote control or on the video phone call each other video Terminal number. Usually video Terminal has a communication book, users can often call video Terminal number to the address book, then call directly in the address book, select the other Terminal. (2) multipoint videoconference videoconference mainly apply to multipoint video conferencing, business management Terminal consists of a user control to accommodate large groups held meetings, distance learning, and other applications. Users simply log in through a Web browser session, the administrative interface (http://video.cnuninet.com), enter the user account and password, select registration Terminal, set the session duration and other parameters, can be held more Visual Conference. Users can choose to immediately convene a meeting, or you can make an appointment at a particular moment of the meeting. You can held a provincial, national and world-wide meeting. The meeting started, users also can manage Terminal logon session, the administrative interface to control your own sessions. The main venue of the Conference can be implemented to control features include: toggle screen, split-screen select (select in split-screen transfer from Terminal), mute, mute, view Symposium, voice, incentive, invited the meeting to join the, extension of the Terminal and end the meeting, the Chairman of the President of the control mode, control transfer, etc. Symposium achievable Conference control features include: application, application, control, etc. (3) dial the fixed telephone, mobile phone via videoconference terminals can call fixed line or mobile phones; when the user travels in the outer side there is no video conferencing Terminal, also by telephone or mobile phone easy to join the meeting. (4) transfer of picture and text information in the meeting can also be transmitted through the Terminal images and texts.