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Key Technology <br> video conference system transmitted video conference system is multimedia data, the data amount of sound source signal and a moving image is large, it can not be transferred to a digital line general conditions. At the same time, based on the requirements of the actual use effect, the transmitted sound and image signals are required to be continuously smooth, and other auxiliary functions are easy to use. Therefore, the system has high technical requirements in terms of sound/image compression, communication line conditions, and data/application sharing. This article will discuss the main technologies, solutions, future technology trends and network technology standards of videoconferencing, and hope to provide reference for R&D personnel in this field.
1) Multimedia information processing technology
Multimedia information processing technology mainly compresses and processes various media information. The development of video conferencing 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, which in turn promotes the development of video conferencing technology. Especially under the condition that the network bandwidth is not rich, multimedia information compression technology has become one of the most critical issues of video conferencing.
Compared with PC-based CPU technology and based on dedicated chipset technology, the media processor makes the application simpler because of its unique digital video and audio input and output interface, multimedia coprocessor, etc., and equipment manufacturers can change according to market changes. The software application is adjusted to meet market demands in a timely manner, and is not subject to the technical limitations of the dedicated chipset itself. The embedded operating system and software optimization supported by the media processor make the video conferencing system more efficient, stable and reliable. Media processor technology has in fact become the core chip technology of video conferencing, and will serve terminal products such as 3G video phones in the future.
In the video conferencing system , the current media processors mainly include: Philip's TriMedia series and new PNX1500, US ESS's LVP, ADI's ADSP2106X device and Blackfin processor, TI's C6X, C8X and the new DM642. Multimedia DSP chips, these media processors can realize video conferencing communication terminals suitable for different protocols with high-speed computing capabilities. These chips can be used to easily implement MPEG video and audio processing, H.263 video processing, and other multimedia applications such as DVDs, digital set-top boxes, digital TVs, and the like.
2) Broadband network technology The rapidly developing IP network, because it is oriented to a non-connected network, is not suitable for transmitting real-time multimedia information, but the TCP/IP protocol does not fundamentally transmit multimedia data. limit. At present, the world's major standardization organizations, industry alliances, and major companies are improving the transmission protocols on IP networks, and have achieved initial results, such as RTP/RTCP, RSVP, and IPv6. It has laid a good foundation for the development of multimedia services such as video conferencing on IP networks. It is predicted that the video conferencing service on the IP network will greatly exceed the video conferencing service on the circuit switched network.
The network scale and number of users on the Internet are developing rapidly. How to further expand the types of services running on the Internet and improve the service quality of the network is the most concerned issue. Since the IP protocol is a connectionless protocol, there is no concept of quality of service in the Internet. It cannot guarantee sufficient throughput and meet the required transmission delay. It only does its best to meet the needs of users, so if not By adopting new methods to improve the current network environment, it is impossible to develop new services on a large scale.
In the existing network technology, from the perspective of supporting QoS, ATM has a unique technical advantage as a fast packet switching technology that has been rapidly developed after IP. ATM was once considered a universally applicable technology, and people will eventually establish a pure ATM network that can reach another desktop terminal through the core of the network. However, practice has proved that this idea is wrong. First of all, the implementation of pure ATM networks is too complicated, resulting in high application prices, which are difficult to be accepted by the public. Secondly, at the same time of the development of the network, the corresponding business development has not kept up, leading to the current difficult development of ATM. Third, although ATM switches have been widely used as backbone nodes of the network, the development of ATM cells to the desktop is very slow.
Since IP technology and ATM technology have encountered practical difficulties in their respective development fields, and each other needs to rely on each other for further development, the combination of these two technologies is inevitable. Multi-Protocol Label Switching (MPLS) technology is developed to take advantage of the advantages of the network core switching technology and the network edge IP routing technology. Its characteristics are as follows:
(1) Based on a single forwarding mechanism, multiple types of service types can be simultaneously supported in the same network; (2) The shortest fixed label is used to replace the traditional router's longest matching path-finding method with an accurate matching path finding method; 3) Through the integration of link layer (ATM, frame relay) and network layer routing technology, it solves the problem of Internet extension and guarantees IP QoS transmission; (4) Simultaneously passes signaling protocol with QoS parameters by using explicit routing function The establishment of a restricted label switched path (CR-LSP) enables efficient implementation of traffic engineering for the whole country. At present, MPLS technology still has many difficulties in many aspects such as QoS label allocation signaling, solution VC merging, and transmission classification service, and needs further improvement.
3) Distributed processing technology Video conferencing realizes real-time synchronous interactive communication between point-to-point, point-to-multipoint, and multi-point. The video conferencing system requires the synchronization and coordination of the terminals of different media and different locations, and the multi-point control unit (MCU) effectively controls the data in a unified manner, so that the data of the participating terminals can be shared, and the synchronous transmission of various media can be effectively coordinated, so that the system is more humanized. Information exchange and processing methods. Communication, cooperation and coordination are the requirements of distributed processing and the basic connotation of the Interactive Multimedia Collaborative Work System (CSCW). So in this sense, the video conferencing system is one of the main groupware systems of CSCW.
The video conferencing system transmits multimedia data, and the source signal of the sound and the moving image has a large amount of data and cannot be transmitted on a digital line of a general condition. At the same time, based on the requirements of the actual use effect, the transmitted sound and image signals are required to be continuously smooth, and other auxiliary functions are easy to use. Therefore, the system has high technical requirements in terms of sound/image compression, communication line conditions, and data/application sharing. This article will discuss the main technologies, solutions, future technology trends and network technology standards of videoconferencing, and hope to provide reference for R&D personnel in this field.
1) Multimedia information processing technology
Multimedia information processing technology mainly compresses and processes various media information. The development of video conferencing 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, which in turn promotes the development of video conferencing technology. Especially under the condition that the network bandwidth is not rich, multimedia information compression technology has become one of the most critical issues of video conferencing.
Compared with PC-based CPU technology and based on dedicated chipset technology, the media processor makes the application simpler because of its unique digital video and audio input and output interface, multimedia coprocessor, etc., and equipment manufacturers can change according to market changes. The software application is adjusted to meet market demands in a timely manner, and is not subject to the technical limitations of the dedicated chipset itself. The embedded operating system and software optimization supported by the media processor make the video conferencing system more efficient, stable and reliable. Media processor technology has in fact become the core chip technology of video conferencing, and will serve terminal products such as 3G video phones in the future.
In the video conferencing system , the current media processors mainly include: Philip's TriMedia series and new PNX1500, US ESS's LVP, ADI's ADSP2106X device and Blackfin processor, TI's C6X, C8X and the new DM642. Multimedia DSP chips, these media processors can realize video conferencing communication terminals suitable for different protocols with high-speed computing capabilities. These chips can be used to easily implement MPEG video and audio processing, H.263 video processing, and other multimedia applications such as DVDs, digital set-top boxes, digital TVs, and the like.
2) Broadband network technology The rapidly developing IP network, because it is oriented to a non-connected network, is not suitable for transmitting real-time multimedia information, but the TCP/IP protocol does not fundamentally transmit multimedia data. limit. At present, the world's major standardization organizations, industry alliances, and major companies are improving the transmission protocols on IP networks, and have achieved initial results, such as RTP/RTCP, RSVP, and IPv6. It has laid a good foundation for the development of multimedia services such as video conferencing on IP networks. It is predicted that the video conferencing service on the IP network will greatly exceed the video conferencing service on the circuit switched network.
The network scale and number of users on the Internet are developing rapidly. How to further expand the types of services running on the Internet and improve the service quality of the network is the most concerned issue. Since the IP protocol is a connectionless protocol, there is no concept of quality of service in the Internet. It cannot guarantee sufficient throughput and meet the required transmission delay. It only does its best to meet the needs of users, so if not By adopting new methods to improve the current network environment, it is impossible to develop new services on a large scale.
In the existing network technology, from the perspective of supporting QoS, ATM has a unique technical advantage as a fast packet switching technology that has been rapidly developed after IP. ATM was once considered a universally applicable technology, and people will eventually establish a pure ATM network that can reach another desktop terminal through the core of the network. However, practice has proved that this idea is wrong. First of all, the implementation of pure ATM networks is too complicated, resulting in high application prices, which are difficult to be accepted by the public. Secondly, at the same time of the development of the network, the corresponding business development has not kept up, leading to the current difficult development of ATM. Third, although ATM switches have been widely used as backbone nodes of the network, the development of ATM cells to the desktop is very slow.
Since IP technology and ATM technology have encountered practical difficulties in their respective development fields, and each other needs to rely on each other for further development, the combination of these two technologies is inevitable. Multi-Protocol Label Switching (MPLS) technology is developed to take advantage of the advantages of the network core switching technology and the network edge IP routing technology. Its characteristics are as follows:
(1) Based on a single forwarding mechanism, multiple types of service types can be simultaneously supported in the same network; (2) The shortest fixed label is used to replace the traditional router's longest matching path-finding method with an accurate matching path finding method; 3) Through the integration of link layer (ATM, frame relay) and network layer routing technology, it solves the problem of Internet extension and guarantees IP QoS transmission; (4) Simultaneously passes signaling protocol with QoS parameters by using explicit routing function The establishment of a restricted label switched path (CR-LSP) enables efficient implementation of traffic engineering for the whole country. At present, MPLS technology still has many difficulties in many aspects such as QoS label allocation signaling, solution VC merging, and transmission classification service, and needs further improvement.
3) Distributed processing technology Video conferencing realizes real-time synchronous interactive communication between point-to-point, point-to-multipoint, and multi-point. The video conferencing system requires the synchronization and coordination of the terminals of different media and different locations, and the multi-point control unit (MCU) effectively controls the data in a unified manner, so that the data of the participating terminals can be shared, and the synchronous transmission of various media can be effectively coordinated, so that the system is more humanized. Information exchange and processing methods. Communication, cooperation and coordination are the requirements of distributed processing and the basic connotation of the Interactive Multimedia Collaborative Work System (CSCW). So in this sense, the video conferencing system is one of the main groupware systems of CSCW.
The video conferencing system transmits multimedia data, and the source signal of the sound and the moving image has a large amount of data and cannot be transmitted on a digital line of a general condition. At the same time, based on the requirements of the actual use effect, the transmitted sound and image signals are required to be continuously smooth, and other auxiliary functions are easy to use. Therefore, the system has high technical requirements in terms of sound/image compression, communication line conditions, and data/application sharing. This article will discuss the main technologies, solutions, future technology trends and network technology standards of videoconferencing, and hope to provide reference for R&D personnel in this field.
1) Multimedia information processing technology
Multimedia information processing technology mainly compresses and processes various media information. The development of video conferencing 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, which in turn promotes the development of video conferencing technology. Especially under the condition that the network bandwidth is not rich, multimedia information compression technology has become one of the most critical issues of video conferencing.
Compared with PC-based CPU technology and based on dedicated chipset technology, the media processor makes the application simpler because of its unique digital video and audio input and output interface, multimedia coprocessor, etc., and equipment manufacturers can change according to market changes. The software application is adjusted to meet market demands in a timely manner, and is not subject to the technical limitations of the dedicated chipset itself. The embedded operating system and software optimization supported by the media processor make the video conferencing system more efficient, stable and reliable. Media processor technology has in fact become the core chip technology of video conferencing, and will serve terminal products such as 3G video phones in the future.
In the video conferencing system , the current media processors mainly include: Philip's TriMedia series and new PNX1500, US ESS's LVP, ADI's ADSP2106X device and Blackfin processor, TI's C6X, C8X and the new DM642. Multimedia DSP chips, these media processors can realize video conferencing communication terminals suitable for different protocols with high-speed computing capabilities. These chips can be used to easily implement MPEG video and audio processing, H.263 video processing, and other multimedia applications such as DVDs, digital set-top boxes, digital TVs, and the like.
2) Broadband network technology The rapidly developing IP network, because it is oriented to a non-connected network, is not suitable for transmitting real-time multimedia information, but the TCP/IP protocol does not fundamentally transmit multimedia data. limit. At present, the world's major standardization organizations, industry alliances, and major companies are improving the transmission protocols on IP networks, and have achieved initial results, such as RTP/RTCP, RSVP, and IPv6. It has laid a good foundation for the development of multimedia services such as video conferencing on IP networks. It is predicted that the video conferencing service on the IP network will greatly exceed the video conferencing service on the circuit switched network.
The network scale and number of users on the Internet are developing rapidly. How to further expand the types of services running on the Internet and improve the service quality of the network is the most concerned issue. Since the IP protocol is a connectionless protocol, there is no concept of quality of service in the Internet. It cannot guarantee sufficient throughput and meet the required transmission delay. It only does its best to meet the needs of users, so if not By adopting new methods to improve the current network environment, it is impossible to develop new services on a large scale.
In the existing network technology, from the perspective of supporting QoS, ATM has a unique technical advantage as a fast packet switching technology that has been rapidly developed after IP. ATM was once considered a universally applicable technology, and people will eventually establish a pure ATM network that can reach another desktop terminal through the core of the network. However, practice has proved that this idea is wrong. First of all, the implementation of pure ATM networks is too complicated, resulting in high application prices, which are difficult to be accepted by the public. Secondly, at the same time of the development of the network, the corresponding business development has not kept up, leading to the current difficult development of ATM. Third, although ATM switches have been widely used as backbone nodes of the network, the development of ATM cells to the desktop is very slow.
Since IP technology and ATM technology have encountered practical difficulties in their respective development fields, and each other needs to rely on each other for further development, the combination of these two technologies is inevitable. Multi-Protocol Label Switching (MPLS) technology is developed to take advantage of the advantages of the network core switching technology and the network edge IP routing technology. Its characteristics are as follows:
(1) Based on a single forwarding mechanism, multiple types of service types can be simultaneously supported in the same network; (2) The shortest fixed label is used to replace the traditional router's longest matching path-finding method with an accurate matching path finding method; 3) Through the integration of link layer (ATM, frame relay) and network layer routing technology, it solves the problem of Internet extension and guarantees IP QoS transmission; (4) Simultaneously passes signaling protocol with QoS parameters by using explicit routing function The establishment of a restricted label switched path (CR-LSP) enables efficient implementation of traffic engineering for the whole country. At present, MPLS technology still has many difficulties in many aspects such as QoS label allocation signaling, solution VC merging, and transmission classification service, and needs further improvement.
3) Distributed processing technology Video conferencing realizes real-time synchronous interactive communication between point-to-point, point-to-multipoint, and multi-point. The video conferencing system requires the synchronization and coordination of the terminals of different media and different locations, and the multi-point control unit (MCU) effectively controls the data in a unified manner, so that the data of the participating terminals can be shared, and the synchronous transmission of various media can be effectively coordinated, so that the system is more humanized. Information exchange and processing methods. Communication, cooperation and coordination are the requirements of distributed processing and the basic connotation of the Interactive Multimedia Collaborative Work System (CSCW). So in this sense, the video conferencing system is one of the main groupware systems of CSCW.
Key Technology <br> video conference system transmitted video conference system is multimedia data, the data amount of sound source signal and a moving image is large, it can not be transferred to a digital line general conditions. At the same time, based on the requirements of the actual use effect, the transmitted sound and image signals are required to be continuously smooth, and other auxiliary functions are easy to use. Therefore, the system has high technical requirements in terms of sound/image compression, communication line conditions, and data/application sharing. This article will discuss the main technologies, solutions, future technology trends and network technology standards of videoconferencing, and hope to provide reference for R&D personnel in this field.
1) Multimedia information processing technology
Multimedia information processing technology mainly compresses and processes various media information. The development of video conferencing 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, which in turn promotes the development of video conferencing technology. Especially under the condition that the network bandwidth is not rich, multimedia information compression technology has become one of the most critical issues of video conferencing.
Compared with PC-based CPU technology and based on dedicated chipset technology, the media processor makes the application simpler because of its unique digital video and audio input and output interface, multimedia coprocessor, etc., and equipment manufacturers can change according to market changes. The software application is adjusted to meet market demands in a timely manner, and is not subject to the technical limitations of the dedicated chipset itself. The embedded operating system and software optimization supported by the media processor make the video conferencing system more efficient, stable and reliable. Media processor technology has in fact become the core chip technology of video conferencing, and will serve terminal products such as 3G video phones in the future.
In the video conferencing system , the current media processors mainly include: Philip's TriMedia series and new PNX1500, US ESS's LVP, ADI's ADSP2106X device and Blackfin processor, TI's C6X, C8X and the new DM642. Multimedia DSP chips, these media processors can realize video conferencing communication terminals suitable for different protocols with high-speed computing capabilities. These chips can be used to easily implement MPEG video and audio processing, H.263 video processing, and other multimedia applications such as DVDs, digital set-top boxes, digital TVs, and the like.
2) Broadband network technology The rapidly developing IP network, because it is oriented to a non-connected network, is not suitable for transmitting real-time multimedia information, but the TCP/IP protocol does not fundamentally transmit multimedia data. limit. At present, the world's major standardization organizations, industry alliances, and major companies are improving the transmission protocols on IP networks, and have achieved initial results, such as RTP/RTCP, RSVP, and IPv6. It has laid a good foundation for the development of multimedia services such as video conferencing on IP networks. It is predicted that the video conferencing service on the IP network will greatly exceed the video conferencing service on the circuit switched network.
The network scale and number of users on the Internet are developing rapidly. How to further expand the types of services running on the Internet and improve the service quality of the network is the most concerned issue. Since the IP protocol is a connectionless protocol, there is no concept of quality of service in the Internet. It cannot guarantee sufficient throughput and meet the required transmission delay. It only does its best to meet the needs of users, so if not By adopting new methods to improve the current network environment, it is impossible to develop new services on a large scale.
In the existing network technology, from the perspective of supporting QoS, ATM has a unique technical advantage as a fast packet switching technology that has been rapidly developed after IP. ATM was once considered a universally applicable technology, and people will eventually establish a pure ATM network that can reach another desktop terminal through the core of the network. However, practice has proved that this idea is wrong. First of all, the implementation of pure ATM networks is too complicated, resulting in high application prices, which are difficult to be accepted by the public. Secondly, at the same time of the development of the network, the corresponding business development has not kept up, leading to the current difficult development of ATM. Third, although ATM switches have been widely used as backbone nodes of the network, the development of ATM cells to the desktop is very slow.
Since IP technology and ATM technology have encountered practical difficulties in their respective development fields, and each other needs to rely on each other for further development, the combination of these two technologies is inevitable. Multi-Protocol Label Switching (MPLS) technology is developed to take advantage of the advantages of the network core switching technology and the network edge IP routing technology. Its characteristics are as follows:
(1) Based on a single forwarding mechanism, multiple types of service types can be simultaneously supported in the same network; (2) The shortest fixed label is used to replace the traditional router's longest matching path-finding method with an accurate matching path finding method; 3) Through the integration of link layer (ATM, frame relay) and network layer routing technology, it solves the problem of Internet extension and guarantees IP QoS transmission; (4) Simultaneously passes signaling protocol with QoS parameters by using explicit routing function The establishment of a restricted label switched path (CR-LSP) enables efficient implementation of traffic engineering for the whole country. At present, MPLS technology still has many difficulties in many aspects such as QoS label allocation signaling, solution VC merging, and transmission classification service, and needs further improvement.
3) Distributed processing technology Video conferencing realizes real-time synchronous interactive communication between point-to-point, point-to-multipoint, and multi-point. The video conferencing system requires the synchronization and coordination of the terminals of different media and different locations, and the multi-point control unit (MCU) effectively controls the data in a unified manner, so that the data of the participating terminals can be shared, and the synchronous transmission of various media can be effectively coordinated, so that the system is more humanized. Information exchange and processing methods. Communication, cooperation and coordination are the requirements of distributed processing and the basic connotation of the Interactive Multimedia Collaborative Work System (CSCW). So in this sense, the video conferencing system is one of the main groupware systems of CSCW.
The video conferencing system transmits multimedia data, and the source signal of the sound and the moving image has a large amount of data and cannot be transmitted on a digital line of a general condition. At the same time, based on the requirements of the actual use effect, the transmitted sound and image signals are required to be continuously smooth, and other auxiliary functions are easy to use. Therefore, the system has high technical requirements in terms of sound/image compression, communication line conditions, and data/application sharing. This article will discuss the main technologies, solutions, future technology trends and network technology standards of videoconferencing, and hope to provide reference for R&D personnel in this field.
1) Multimedia information processing technology
Multimedia information processing technology mainly compresses and processes various media information. The development of video conferencing 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, which in turn promotes the development of video conferencing technology. Especially under the condition that the network bandwidth is not rich, multimedia information compression technology has become one of the most critical issues of video conferencing.
Compared with PC-based CPU technology and based on dedicated chipset technology, the media processor makes the application simpler because of its unique digital video and audio input and output interface, multimedia coprocessor, etc., and equipment manufacturers can change according to market changes. The software application is adjusted to meet market demands in a timely manner, and is not subject to the technical limitations of the dedicated chipset itself. The embedded operating system and software optimization supported by the media processor make the video conferencing system more efficient, stable and reliable. Media processor technology has in fact become the core chip technology of video conferencing, and will serve terminal products such as 3G video phones in the future.
In the video conferencing system , the current media processors mainly include: Philip's TriMedia series and new PNX1500, US ESS's LVP, ADI's ADSP2106X device and Blackfin processor, TI's C6X, C8X and the new DM642. Multimedia DSP chips, these media processors can realize video conferencing communication terminals suitable for different protocols with high-speed computing capabilities. These chips can be used to easily implement MPEG video and audio processing, H.263 video processing, and other multimedia applications such as DVDs, digital set-top boxes, digital TVs, and the like.
2) Broadband network technology The rapidly developing IP network, because it is oriented to a non-connected network, is not suitable for transmitting real-time multimedia information, but the TCP/IP protocol does not fundamentally transmit multimedia data. limit. At present, the world's major standardization organizations, industry alliances, and major companies are improving the transmission protocols on IP networks, and have achieved initial results, such as RTP/RTCP, RSVP, and IPv6. It has laid a good foundation for the development of multimedia services such as video conferencing on IP networks. It is predicted that the video conferencing service on the IP network will greatly exceed the video conferencing service on the circuit switched network.
The network scale and number of users on the Internet are developing rapidly. How to further expand the types of services running on the Internet and improve the service quality of the network is the most concerned issue. Since the IP protocol is a connectionless protocol, there is no concept of quality of service in the Internet. It cannot guarantee sufficient throughput and meet the required transmission delay. It only does its best to meet the needs of users, so if not By adopting new methods to improve the current network environment, it is impossible to develop new services on a large scale.
In the existing network technology, from the perspective of supporting QoS, ATM has a unique technical advantage as a fast packet switching technology that has been rapidly developed after IP. ATM was once considered a universally applicable technology, and people will eventually establish a pure ATM network that can reach another desktop terminal through the core of the network. However, practice has proved that this idea is wrong. First of all, the implementation of pure ATM networks is too complicated, resulting in high application prices, which are difficult to be accepted by the public. Secondly, at the same time of the development of the network, the corresponding business development has not kept up, leading to the current difficult development of ATM. Third, although ATM switches have been widely used as backbone nodes of the network, the development of ATM cells to the desktop is very slow.
Since IP technology and ATM technology have encountered practical difficulties in their respective development fields, and each other needs to rely on each other for further development, the combination of these two technologies is inevitable. Multi-Protocol Label Switching (MPLS) technology is developed to take advantage of the advantages of the network core switching technology and the network edge IP routing technology. Its characteristics are as follows:
(1) Based on a single forwarding mechanism, multiple types of service types can be simultaneously supported in the same network; (2) The shortest fixed label is used to replace the traditional router's longest matching path-finding method with an accurate matching path finding method; 3) Through the integration of link layer (ATM, frame relay) and network layer routing technology, it solves the problem of Internet extension and guarantees IP QoS transmission; (4) Simultaneously passes signaling protocol with QoS parameters by using explicit routing function The establishment of a restricted label switched path (CR-LSP) enables efficient implementation of traffic engineering for the whole country. At present, MPLS technology still has many difficulties in many aspects such as QoS label allocation signaling, solution VC merging, and transmission classification service, and needs further improvement.
3) Distributed processing technology Video conferencing realizes real-time synchronous interactive communication between point-to-point, point-to-multipoint, and multi-point. The video conferencing system requires the synchronization and coordination of the terminals of different media and different locations, and the multi-point control unit (MCU) effectively controls the data in a unified manner, so that the data of the participating terminals can be shared, and the synchronous transmission of various media can be effectively coordinated, so that the system is more humanized. Information exchange and processing methods. Communication, cooperation and coordination are the requirements of distributed processing and the basic connotation of the Interactive Multimedia Collaborative Work System (CSCW). So in this sense, the video conferencing system is one of the main groupware systems of CSCW.
The video conferencing system transmits multimedia data, and the source signal of the sound and the moving image has a large amount of data and cannot be transmitted on a digital line of a general condition. At the same time, based on the requirements of the actual use effect, the transmitted sound and image signals are required to be continuously smooth, and other auxiliary functions are easy to use. Therefore, the system has high technical requirements in terms of sound/image compression, communication line conditions, and data/application sharing. This article will discuss the main technologies, solutions, future technology trends and network technology standards of videoconferencing, and hope to provide reference for R&D personnel in this field.
1) Multimedia information processing technology
Multimedia information processing technology mainly compresses and processes various media information. The development of video conferencing 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, which in turn promotes the development of video conferencing technology. Especially under the condition that the network bandwidth is not rich, multimedia information compression technology has become one of the most critical issues of video conferencing.
Compared with PC-based CPU technology and based on dedicated chipset technology, the media processor makes the application simpler because of its unique digital video and audio input and output interface, multimedia coprocessor, etc., and equipment manufacturers can change according to market changes. The software application is adjusted to meet market demands in a timely manner, and is not subject to the technical limitations of the dedicated chipset itself. The embedded operating system and software optimization supported by the media processor make the video conferencing system more efficient, stable and reliable. Media processor technology has in fact become the core chip technology of video conferencing, and will serve terminal products such as 3G video phones in the future.
In the video conferencing system , the current media processors mainly include: Philip's TriMedia series and new PNX1500, US ESS's LVP, ADI's ADSP2106X device and Blackfin processor, TI's C6X, C8X and the new DM642. Multimedia DSP chips, these media processors can realize video conferencing communication terminals suitable for different protocols with high-speed computing capabilities. These chips can be used to easily implement MPEG video and audio processing, H.263 video processing, and other multimedia applications such as DVDs, digital set-top boxes, digital TVs, and the like.
2) Broadband network technology The rapidly developing IP network, because it is oriented to a non-connected network, is not suitable for transmitting real-time multimedia information, but the TCP/IP protocol does not fundamentally transmit multimedia data. limit. At present, the world's major standardization organizations, industry alliances, and major companies are improving the transmission protocols on IP networks, and have achieved initial results, such as RTP/RTCP, RSVP, and IPv6. It has laid a good foundation for the development of multimedia services such as video conferencing on IP networks. It is predicted that the video conferencing service on the IP network will greatly exceed the video conferencing service on the circuit switched network.
The network scale and number of users on the Internet are developing rapidly. How to further expand the types of services running on the Internet and improve the service quality of the network is the most concerned issue. Since the IP protocol is a connectionless protocol, there is no concept of quality of service in the Internet. It cannot guarantee sufficient throughput and meet the required transmission delay. It only does its best to meet the needs of users, so if not By adopting new methods to improve the current network environment, it is impossible to develop new services on a large scale.
In the existing network technology, from the perspective of supporting QoS, ATM has a unique technical advantage as a fast packet switching technology that has been rapidly developed after IP. ATM was once considered a universally applicable technology, and people will eventually establish a pure ATM network that can reach another desktop terminal through the core of the network. However, practice has proved that this idea is wrong. First of all, the implementation of pure ATM networks is too complicated, resulting in high application prices, which are difficult to be accepted by the public. Secondly, at the same time of the development of the network, the corresponding business development has not kept up, leading to the current difficult development of ATM. Third, although ATM switches have been widely used as backbone nodes of the network, the development of ATM cells to the desktop is very slow.
Since IP technology and ATM technology have encountered practical difficulties in their respective development fields, and each other needs to rely on each other for further development, the combination of these two technologies is inevitable. Multi-Protocol Label Switching (MPLS) technology is developed to take advantage of the advantages of the network core switching technology and the network edge IP routing technology. Its characteristics are as follows:
(1) Based on a single forwarding mechanism, multiple types of service types can be simultaneously supported in the same network; (2) The shortest fixed label is used to replace the traditional router's longest matching path-finding method with an accurate matching path finding method; 3) Through the integration of link layer (ATM, frame relay) and network layer routing technology, it solves the problem of Internet extension and guarantees IP QoS transmission; (4) Simultaneously passes signaling protocol with QoS parameters by using explicit routing function The establishment of a restricted label switched path (CR-LSP) enables efficient implementation of traffic engineering for the whole country. At present, MPLS technology still has many difficulties in many aspects such as QoS label allocation signaling, solution VC merging, and transmission classification service, and needs further improvement.
3) Distributed processing technology Video conferencing realizes real-time synchronous interactive communication between point-to-point, point-to-multipoint, and multi-point. The video conferencing system requires the synchronization and coordination of the terminals of different media and different locations, and the multi-point control unit (MCU) effectively controls the data in a unified manner, so that the data of the participating terminals can be shared, and the synchronous transmission of various media can be effectively coordinated, so that the system is more humanized. Information exchange and processing methods. Communication, cooperation and coordination are the requirements of distributed processing and the basic connotation of the Interactive Multimedia Collaborative Work System (CSCW). So in this sense, the video conferencing system is one of the main groupware systems of CSCW.
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