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Mainstream Solutions and Technology Trends of Video Conference system

Key Technologies of Video Conference system

The video conference system transmits multimedia data, and the source signal of sound and moving image has a large amount of data, so it can not be transmitted on the digital line. At the same time, based on the requirements of the actual use effect, the transmitted sound and image signals are required to be continuous and smooth, and other auxiliary functions are easy to use. Therefore, there are high technical requirements for the system in the aspects of sound / image compression, communication line conditions, data / application sharing and so on. This paper will discuss the main technologies, solutions, future technology trends and network technology standards of video conferencing, hoping to provide reference for researchers in this field.

1) Multimedia information processing technology

Multimedia information processing technology is mainly to compress and process all kinds of media information. The development of video conference also reflects the development of information processing technology, especially video compression technology. At present, new theories and algorithms continue to promote the development of multimedia information processing technology, and then promote the development of video conference technology. Especially when the network bandwidth is not abundant, multimedia information compression technology has become one of the most critical issues in video conferencing.

Compared with PC-based CPU technology and special chipset technology, the application of media processor becomes easier because of its unique digital video and audio input and output interface, multimedia coprocessor and so on. And the equipment manufacturer can adjust the software application at any time according to the market change, adapt to the market demand in time, and is not limited by the technical limitation of the special chipset itself. The embedded operating system and software optimization supported by the media processor make the video conference system more efficient, stable and reliable. In fact, media processor technology has become the core chip technology of video conferencing, and it will also serve terminal products such as 3G videophone in the future.

In the video conference system, the current media processors mainly include Philips' TriMedia series and the new PNX1500,ESS 's LVP,ADI 's ADSP2106X and Blackfin,TI 's C6X and C8X and DM642 multimedia DSP chips. The high-speed computing capabilities of these media processors can realize video conference communication terminals suitable for different protocols. These chips can easily realize MPEG video and audio processing, H.263 video processing, and other multimedia applications such as DVD, digital set-top box, digital TV and so on.

2) the IP network with the rapid development of broadband network technology is not suitable for the transmission of real-time multimedia information because it is an unconnected network, but TCP/IP protocol has no fundamental restrictions on the transmission of multimedia data. At present, the major standardization organizations, industry alliances and companies around the world are improving the transport protocols on the IP network, and have achieved preliminary results, such as RTP/RTCP, RSVP, IPv6 and so on. This lays a good foundation for developing multimedia services such as video conferencing on the IP network. It is predicted that the video conference service on the IP network will greatly exceed the video conference service on the circuit switched network.

With the rapid development of the Internet network scale and the number of users, how to further expand the types of online services and improve the service quality of the network is the most concerned issue at present. Because IP is a connectionless protocol, there is no concept of QoS in Internet network, so it can not guarantee sufficient throughput and transmission delay, so it can only try its best to meet the needs of users. Therefore, if we do not adopt new methods to improve the current network environment, we will not be able to develop new services on a large scale.

Among the existing network technologies, from the point of view of supporting QoS, ATM, as a fast packet switching technology developed rapidly after IP, has unique technical advantages. As a result, ATM was once seen as a ubiquitous technology, and people would eventually build a pure ATM network and reach another desktop terminal through the network core. However, practice has proved that this idea is wrong. First of all, the implementation of pure ATM network is too complex, resulting in high application price, which is difficult to be accepted by the public. Secondly, with the development of the network, the corresponding business development has failed to keep up, resulting in the current development of ATM. Third, although the ATM switch has been widely used as the backbone node of the network, the development of ATM cell to desktop service is very slow.

As both IP technology and ATM technology have encountered practical difficulties in their respective development fields, they both need to rely on each other for further development, so the combination of these two technologies is inevitable. Multi-protocol label switching (MPLS) technology is produced to make comprehensive use of the advantages of the switching technology of the network core and the IP routing technology at the edge of the network. Its characteristics are as follows:

(1) based on a single forwarding mechanism, multiple types of services in the same network can be forwarded at the same time; (2) the longest matching routing method of the traditional router is replaced by an exact matching routing method through a short and fixed label; (3) the problem of Internet expansion and IP QoS transmission is solved through integrated link layer (ATM, frame Relay) and network layer routing technology. (4) using the explicit routing function and establishing CR-LSP through the signaling protocol with QoS parameters, the national traffic engineering can be realized effectively. At present, MPLS technology still has many difficulties in many aspects, such as QoS label distribution signaling, solving VC merging, transmission classification service and so on, which need to be further improved.

3) distributed processing technology video conference realizes real-time synchronous interactive communication among point-to-point, point-to-multipoint and multipoint. The video conference system requires synchronous coordination of receiving and receiving of terminals with different media and different locations, and effective and unified control of multipoint control unit (MCU), so that the participating terminals can share data, effectively coordinate the synchronous transmission of various media, and make the system more humanized in information exchange and processing. Communication, cooperation and coordination are not only the requirements of distributed processing, but also the basic connotation of interactive multimedia cooperative work system (CSCW). Therefore, in this sense, video conference system is one of the main groupware systems of CSCW.

Mainstream media processor solutions

With the wide application of multimedia technology, the design of multimedia equipment with DSP chip has become the focus of attention. However, the demand for programmable media processors is also high. Because multimedia signal processing technology is developing at a high speed.

For example, an early video conference equipment using H.261 encoding video, after the emergence of H.263, it is best to switch to the H.263 standard, and may soon adopt H.264 as the video conference coding standard. There are two requirements, one is the upgrading of equipment, the other is the conversion of a variety of standards. For devices implemented with fixed dedicated chips, both of them are difficult to achieve. However, if DSP is used as the core processor, the first requirement can be achieved by updating the software, and the second requirement can be met appropriately by adding some functional software.

Considering this need, a new type of DSP chip-Media processor (Media Processor) arises at the historic moment, and soon gets wide attention in the industry. Philips, ADI, TI and other semiconductor suppliers are very optimistic about the media processor market, and launched competitive products. The emergence of high processing power chips brings less delay and higher frame rate to video conferencing. For example, TI's TMS320 DM642, Philips's Trimedia and Equator's MAPCA integrate rich multimedia signal interfaces, optimize the processor structure according to the characteristics of multimedia signals, and even embed special coprocessors for special operations to ease the pressure on general processors, such as variable length codecs (LC/VLD) in video coding.

The media processor provides a fully programmable implementation tool for multimedia devices. The media processor inherits the characteristics of the general DSP chip, expands various interface functions for multimedia applications, and optimizes the CPU structure. Although the media processor has not been around for a long time, it has received wide attention, and it can be predicted that the media processor will be quickly applied to the multimedia equipment manufacturing industry.

The multimedia chip SoC of China Star Microelectronics Company balances the requirements of integration, flexibility, cost and power consumption. At present, the multimedia chip products used in video conference system are VC0301P, VC0302 and VC0321. Yu Qing, vice president of the company, said that the multimedia chip of China Star Microelectronics can support a variety of current mainstream audio and video algorithms and support a range of applications from wireless multimedia to high-end video conferencing. On the PC platform, China Star Microelectronics, in cooperation with Microsoft, recently launched a USB2.0-based video instant messaging system, which makes video quality and system stability to a new level.

For video conferencing and other multimedia applications, Philips launched the digital media processor PNX1500, which is a system-on-chip (SoC). According to Jan Koene, Marketing Director of Philips Semiconductor's Advanced Media processing Group, "the latest product, Nexperia PNX1500, has excellent capabilities in running control tasks and digital signal processing tasks, both of which are required by video conferencing systems. These two tasks can be run on a single PNX1500, which is difficult to achieve for competitive scenarios with the same efficiency. The cost of PNX1500 can be reduced by merging hardware modules such as video Imax O, audio Imax O and general interface on BOM. Because all audio and video codec functions are implemented in software, Philips products can easily adapt to new standards, such as H.264. "

TI's new digital media processor TMS320DM642 has three video ports, all of which can be input or output, and supports BT656, 100-megabit Ethernet port, multi-channel audio serial port, 66MHz PCI and so on. It can support real-time compression of four D1 images and 30 frames per second MPEG-2. TI's digital media processor provides not only high-definition video streaming in Microsoft WMV9 format, but also MPEG-4, MPEG-2 and MPEG-1. In addition, the device also supports H.264.

Zheng Xiaolong, senior sales representative of the semiconductor division of TI, said that in addition to providing 720 MHz DM642 samples, TI currently provides mass-produced devices for DM640 and DM641 as well as 600 MHz DM642. These code-compatible digital media processors can expand a variety of clock rates and memory capacity to support a wide range of applications, from video-based portable consumer electronics to video infrastructure devices.

"for Windows Media 9 encoders and decoders, TI's DM642 is the first programmable DSP to successfully pass conformance testing under D1 clarity," said Amir Majidimehr, vice president of Windows Media technology at Microsoft. TI's new 720MHz DM642 helps integrate HD WM9 into a variety of embedded consumer applications with code compatibility and programmability. "

ADI's Blackfin is a high-performance, dual multiplier-adder (MAC) DSP with microprocessor capabilities such as supervised and user mode, memory protection, 8-bit mathmatics and multimedia processing extensions. Blackfin processor can be used not only as the main audio and video processor, but also as the main processor of graphical user interface (GUI) and network processing. Blackfin is fully programmable. As a result, new standards can be easily supported without changing the hardware platform. For example, the Blackfin processor in the ADI videophone platform can support H.264, which is achieved through software upgrades.

According to Dan Ivanciw, Product Marketing Manager of the Software and Systems Technology Department of ADI, the Blackfin processor architecture has been optimized to perform control and digital algorithms well, and can be used as the main processor and audio and video processor. " Designers do not need to use multiple different processors, different development environments and different toolkits, whether they are developing typical main function codes or advanced audio and video codec, using Blackfin, the development team only needs to master a programming method, instruction system, and development tool environment. Users will also benefit: shorten product time to market, reduce development costs, reduce development risk, and improve IP reuse. "

In the field of multimedia signal processing, especially in video processing, digital signal processors are usually required to have optimized kernel structures and rich media interfaces for multimedia applications, but the performance of general-purpose signal processors can not be brought into full play in this aspect. In view of this, Equator Company of the United States has launched a series of BSP high-speed broadband digital signal processors. BSP-15 is one of the series and is inversely compatible with MAP-CA.

BSP-15 is an efficient DSP specially designed for video applications, which meets the needs of broadband products with a highly integrated single chip. At the clock rate of 400MHz, BSP-15 has a processing capacity of 40 GOPS (40 billion integer operations per second), and its processing speed is 8.5 times that of Pentium III, 1.33 times that of the same series of MAP-CA chips, and more than 10 times that of other solutions. The core function of BSP-15 is to use software designed for high-performance, large video stream broadband applications. Combined with iMMediaTools software development environment and its video and audio library, BSP-15 can provide efficient solutions for digital video and image applications.

According to a video conference product R & D engineer, selecting BSP-15 chip for video and audio system design has three advantages: first, BSP-15 is specially designed for video image processing, which can provide high-quality video effect; second, BSP-15 has rich on-chip I-An O interface, so it does not need to add too many peripherals, so it can reduce the cost of the whole system and the complexity of design. Third, completely use C language programming, no assembly language requirements, easy to upgrade, high flexibility. Compared with the same series of TI DSP and Philip's Trimedia series DSP, the deficiency of BSP-15 is that the software development is more difficult and the stability is suspected. However, because of its excellent processing performance, BSP-15 processors will still occupy a large market in consumer electronic products, video conferencing, digital image processing and so on.

Last year, Israel VCON Communications Co., Ltd. launched a high-performance video conference codec-HD100 video conference engine based on the new generation of Equator BSP-15 multimedia processors. Gordon Daugherty, Chief Marketing Officer of VCON, said: "the quality of video conference is getting closer and closer to that of radio and television, and the video conference market has entered a new stage. VCON integrators can take advantage of the compact size and high audio and video quality of the HD100 video conference engine to build a variety of advanced multimedia conference applications at a very competitive cost."

Technical Trends of Future Video Conferencing

As the delay problem is gradually solved by IETF technologies and standards (such as multicast technology, bandwidth reservation protocol and real-time control protocol), the video conference scheme based on IP combines terminal interoperability with high transmission performance. As far as the standard is concerned, resource reservation protocol (RSVP) helps to avoid network congestion and ensures the transmission quality of video conferencing; although real-time transport protocol (RTP) can not guarantee the integrity of data transmission, it can use timestamp method to deal with the timing relationship, so that the sequence of data in the transmission process will not be disturbed. Video communication will become easier, the cost will be lower, the traditional conference mode has been far from being able to meet the needs of the network era. As an application system that supports people to exchange real-time information and carry out collaborative work over a long distance, video conference system enables collaborative members to communicate intuitively and truly over long distances.

Dan Ivanciw, Product Marketing Manager, Software and Systems Technology Department of ADI, believes that one of the trends in video conferencing technology is the need for video codec technology with higher compression ratio, and networks with improvements in quality of service and security. Today's fixed and inflexible video conferencing products need to be replaced, or take expensive hardware upgrades to be compatible, or take advantage of these changes and improvements in the future. Another trend is the convergence of IP-based video services and VoIP products. The third general trend is that service providers provide IP video value-added services to a wider range of residential and business customers. This is also true in most product areas, where users always want to add more features, such as three-way or multi-party audio and video conferencing. Additional capabilities require the end device to have more processing power, but infrastructure requirements can be reduced by incorporating some performance into the end device.

Philips Semiconductor's Jan Koene also believes that the main trend of video conferencing is more advanced codec technology, such as H.264 compliance; another trend is that POTS (PSTN)-based video conference systems will be transformed into IP-based systems; the third trend is that the resolution will increase from the existing CIF level to SD level, or even HD level.

Yu Qing of Zhongxing Microelectronics said that in addition to the need for high-quality / low-bit-rate video compression technology suitable for video conference terminals, error resilience technology in the video conference application layer and QoS control technology on the video conference server side are also important technology development trends in video conferencing.

Wang Liang, an engineer in the video system department of ZTE Corporation, summed up the development trend of video conference as the "four modernizations" construction:

1. The system has the function of simultaneous interpretation of picture and text: in addition to video and audio, it can easily transmit and display computer documents for training, reporting and communication; the video conference is integrated with the telephone system: it is easy to access the conference telephone system. You can also join the meeting by phone or mobile phone. Video conference and office automation (OA) system are organically combined to achieve the following functions: meeting organization, meeting mail notification, meeting control, system maintenance and upgrade on OA network; personal visual calls and multi-party meetings on OA network; OA network can only use ordinary PC to learn conference or training content at any time; centralized command, remote scheduling-video wall display overview of the overall situation, access to telephone remote command.

two。 Diversification of system networking

Meetings can be held if there is a network, and all kinds of multimedia terminals can be accessed through the existing networks such as dedicated line, ISDN, IP (ADSL, LAN access), telephone and so on.

3. Image sharpening

Video conferencing needs better, clearer and more mature image codec technology.

4. Simplification of use and maintenance

Easy to use, can organize and control meetings; remote management, remote maintenance, upgrade, reduce maintenance costs; update the design, greatly improve the stability of the system.

Chen Chongjun, head of the Marketing Engineering Department of Huawei's multimedia product line, pointed out that the future development of video conferencing first needs more advanced audio and video codec technology and more professional image and voice front and back-end processing technology; second, it should be able to integrate with the next generation network, such as supporting IPv6; and third, it needs terminal technology with higher integration and stronger processing power. He further explained that video codec technology will develop to H.264, voice technology will develop to high fidelity and low bandwidth; MCU will converge to switches and routers; as the network becomes broadband, video conference terminals will also be intelligent, and its development direction will be miniaturized, all-information home network center broadband intelligent terminals, integrating communication, entertainment, information and other functions.

Network Technical Standards promote the Development of Video Conferencing

The formulation of network technical standards has laid the foundation for multimedia applications. H.323 protocol is an IP network multimedia communication standard, which solves the problem of interworking and mutual control of equipment from various manufacturers. With the introduction of H.264, video conference can provide higher quality video effect at lower cost, and the video application which can not be realized before due to financial and technical problems is also expected to become a reality. Just as web log (Weblogs) and instant messaging have become important network applications in the past few years, H.264 technology will strongly promote the birth of new video applications.

MPEG-4, which adopts H.264 technology, has made a breakthrough in low bit rate video transmission. It is reported that Tandberg and Polycom have produced products that support H.264, Huawei will announce H.264 products at the end of this year, and Ting Shitong has also announced support for the standard in its long-haul series.

In July 2003, ITU approved the H.239 standard. Based on this technology, video users can get dual-stream video services. According to Yu Baosheng, technical director of Polycom, Polycom's character + content (People+Content) dual-stream technology allows hosts to send both video and content (PowerPoint, browser screen content, etc.) in a video conference. In addition, the scheme provided by the standard is suitable for both signaling-based H.320 and H.245 systems, and can transmit and display multi-channel video information in the conference system at the same time. Companies such as RADVISION, Sony and VCON have also announced support for H.239 and produce related products. Tandberg's Duo Video can also implement this feature.

With the continuous development of various technologies and the introduction of a series of international standards, the situation of video conference technology and equipment dominated by a small number of large companies has been broken, and has gradually developed into a pattern of video conference market jointly divided by foreign businessmen (such as Polycom, Tandberg, VTEL, VCON, etc.) and Chinese local enterprises (such as ZTE, Huawei, Zhongtai, Riverford, etc.). With the rapid development of high-speed IP network and Internet, the application and development of video conference has entered a new period. In the next few years, video technology will be more and more widely used in various fields and become one of the mainstream applications in the information society.

At the end of this article, I hope it will be helpful to you.

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