This paper introduces the development status of multimedia distance education at home and abroad, and points out that there is still a certain gap between China and western developed countries in the types, contents, quality and real-time interaction of distance education. Especially some problems existing in the real-time distance education system, some ideas are put forward.
Keywords multimedia, distance education, development status, real-time performance
Entering the digital and information age of 2 1 century, people's demand for education is increasing. As a new educational model, multimedia distance education will make full use of existing educational resources, is a new educational form, and is an inevitable way to realize the popularization, modernization, lifelong and internationalization of higher education. At the same time, the development of modern computer technology, network technology, communication technology, multimedia technology, database technology and artificial intelligence technology provides a strong technical guarantee for the development of multimedia distance education.
1. Definition and classification of distance education
Desmond Keegan once defined five elements for distance education: students and teachers are geographically separated, not face to face; Qualification certification of educational institutions by government education departments; Apply modern communication technology; Provide two-way interactive function; Students can attend classes anytime and anywhere. Its biggest feature is remote and interactive.
From a technical point of view, distance education can be divided into postal mode, radio and television mode, Internet mode and telecommunication network mode. The first two models have formed a certain scale. At present, the international research on distance education mainly focuses on the latter two modes.
Internet-based model
In this way, the WWW technology of the Internet and other applications such as browser, email, FTP and BBS are used to realize a completely independent teaching mode in time and place. You can organize online discussions and use the Internet to set up online schools. Students can enhance their autonomy and gradually form a "self-arranged learning environment, which is guided by experts and excellent teachers and is not limited by time and space". Students can debate the questions raised in the course through electronic "virtual dialogue" and invite internet visitors to join the "class discussion", which is a good supplement to the course.
Based on telecom network mode
The way based on telecommunication network is to arrange the school classrooms at the far end, which can solve the problem of insufficient school classrooms. The students are listening to an excellent teacher in several remote classrooms at the same time. Technically, the high data transmission and reliability of the telecommunication network are utilized. There are generally three parts: studio (central classroom), remote classroom and communication network.
2. The development status of multimedia distance education at home and abroad.
The development of computer from single computer to network has touched the traditional education model. Among all kinds of educational models, distance education is one of the most active and promising fields. This educational reform does not mean that computers should replace the role of teachers, but should be used as an effective tool to assist teaching.
Present situation of foreign development
Worldwide, the arrival of the information society in the network era is pushing the school education reform step by step, the campus wall is gradually disappearing, and a new educational model for students to study in the network virtual school is quietly emerging.
1In August, 1996, ten states, including California and Texas, jointly established a virtual university recognized by all states and universities. Students attend classes, take exams and get degree certificates in electronic classrooms, which officially opens the prelude of online distance education. At present, 80 universities in the United States have obtained degrees through the Internet, and the courses offered by online virtual universities have covered all major disciplines. For example, NTU University of Science and Technology offered 16 courses in chemical engineering, bridge engineering and business administration in the summer school year of 198. The University of Wisconsin built its first electronic classroom on 1998 1 month, offering 17 courses in five categories: business, literature, education, library science and social science. Education committees in the southern United States, mainly in Atlanta and Georgia, began to broadcast the courses of 50 southern universities through the Internet. At the same time, the United States has begun to pay attention to the infrastructure construction of primary and secondary schools. 1996, American President Bill Clinton put forward the "Educational Technology Initiative". The action plan points out that by the year 2000, every classroom and every library in the United States will be connected with the information superhighway, so that every child can receive education in the science and technology culture of the 2 1 century.
In addition, Canada, Britain and other western countries are also vigorously developing online distance education; For example, the College of Distance Education and Continuing Education of the University of Waterloo in Canada facilitates students to enter the virtual classroom to complete all courses of literature, science and environment required by the university. The university offers more than 250 courses to choose from, and offers a part-time master's course in technical management, where you can study while working. Simon Flesh University offers 28 courses in geography, history and psychology. The Open University in Britain offers eleven courses, including mathematics, agriculture and structural engineering.
Domestic development status quo
Compared with western developed countries, the application of network technology in China is relatively late. 1At the end of 1995, CERNET, the first computer internet covering the whole country in China, was formally established and put into use. Limited by technical conditions, the research work of online distance education in China began after the completion of CERNET, but it developed rapidly. At present, Tsinghua University, Peking University, Shanghai Jiaotong University, Tongji University, South China University of Technology, Beijing Medical University, Zhongshan Medical University, China Renmin University, Hunan University, South China Normal University, China University of Science and Technology, Changchun University of Posts and Telecommunications, Liaoning University, Zhejiang University, Beijing Radio and TV University, Guangdong Radio and TV University, Zhejiang Radio and TV University and Xi Jiaotong University all provide their own services. In addition, some middle schools such as Beijing 10 1 Middle School, Shenzhen Middle School, high school affiliated to nanjing normal university and Jiangsu Normal Middle School have also set up online distance education websites, such as COL Online School, Yunzhou Online School, Xinjiang Distance Education Resource Network, Jilin Education and Teaching Network and Wan Heng Distance Education Network.
3. Problems existing in multimedia distance education in China.
When developed countries such as the United States have popularized computer multimedia network education to the stage of early childhood education, our universities have just begun to enter the field of distance education. Therefore, compared with western developed countries, there is still a big gap in the types of courses offered, the quality of course content and real-time interaction. Remote service sites in most universities only provide courseware teaching services based on WWW. Some of these courseware teaching are conducted in the form of multimedia, while others are even just courseware teaching with words and pictures. Only a few distance education outlets in colleges and universities have added modules for testing, management and real-time text and voice communication (such as Tsinghua, Peking University and Shanghai Jiaotong University).
In particular, the real-time distance education model needs to be developed urgently. Students are taught by an excellent teacher in multiple remote classrooms at the same time, which still lacks good interaction. Although some schools have successfully implemented it, such as Hunan University and Zhejiang University, the distance education system with advanced two-way interactive technology has been officially launched, and the distance education system in Guangxi has also been completed recently. However, for most colleges and universities, the real-time distance education system is a difficult and key point to be solved urgently. At present, the biggest problem of real-time distance education in China is poor interactivity. Electronic classrooms in many schools still follow the traditional audio-visual teaching mode. The teacher said inside that students can only listen outside, but the media has been transferred from TV to computer monitor.
4. Some ideas about real-time distance education system.
Introduction to CSCW concept
Computer-Supported Cooperative Work (CSCW) is a new computer application mode that has emerged in recent years. It shows that there has been a new breakthrough in computer application, from supporting individual work to supporting group work in the past. Users in the group can exchange information, discuss problems and complete a task together through computers.
Generally speaking, CSCW refers to people in a certain group who, with the help of computers, perform the same tasks and provide them with an interface to enjoy the environment. The group can be one or more units, projects or groups. But what is particularly emphasized here is that people in the group must perform the same tasks, and CSCW provides them with a * * * working environment and friendly and flexible computer interaction means. CSCW is a new research field, which studies how groups work and how various technologies, especially computer technology, support group work.
The real-time distance education model we discussed is based on centralized CSCW system and multimedia communication.
Interactivity of system
In the real-time distance education system, how do teachers keep asking questions to students during the lecture? Can you set aside some time to ask questions or answer students' questions after class?
Video conference system is a good reference model, which can organically combine real-time online distance education based on video conference system with autonomous distance education based on WWW. Conversations between teachers and students, between students and students, and simultaneous access to * * * media will lead to concurrency control problems. Concurrent access to * * * media is an important design problem in distributed network system. Most researchers believe that at a certain time, only one visitor should access the media. Set the teacher to enjoy the highest power in the whole system. He controls communication and access to the whiteboard. All authorization requests are sent to the teacher, and the teacher can authorize one of the students according to the situation. Teachers can also revoke students' authorization at any time.
Communication mode of the system
The main communication mode in the system is point-to-multipoint communication. There are usually two kinds of point-to-multipoint communication methods: broadcast communication and multicast communication. The way of broadcast communication is that messages are sent from one point to all endpoints on the network, and the software running on these endpoints will judge whether the received messages are addressed to themselves, accept them if they are addressed to themselves, or discard them. Multicast communication means that a message is sent from one point to all endpoints on the network waiting for the message, and all endpoints use the same address for multicast communication.
The transmission medium of the system is the Internet. If broadcast communication is adopted, the message is sent to all machines in the whole network, and then the IP layer of the machine is used to identify whether the message should be received. The internet is all over the world, so it is obviously unrealistic to let all related or unrelated machines participate in sending messages. In addition, because we can transmit multimedia information, the amount of data is large. So if broadcast to every machine on the Internet, it will occupy a lot of network bandwidth and cause network congestion.
The IP protocol on the Internet supports multicast. By filling in the multicast address of IP in the destination address of the message, the call can send the same message to a group of hosts on the whole Internet at the same time.
All machines with IP multicast addresses form a multicast group. A communication group can span multiple physical networks. After each multicast, members of the multicast group will receive the same data. A host can join or leave a multicast group at will, and a host can also join multiple multicast groups at the same time. TCP/IP provides five types of IP addresses: A, B, C, D and E. IP multicast address is a class D address in IP address.
Because the number of multicast groups is limited and can be managed centrally, there is no hierarchy of multicast addresses, and all multicast groups on the Internet adopt a single hierarchy, which is logically equivalent. Each multicast group has a unique multicast address, one is a standard permanent address, which is uniformly distributed by the Internet Central Management Agency (NIC), and the other is a temporary multicast address, which is created as needed. In order to control multicast transmission across multiple physical subnets, TCP/IP provides an Internet Group Management Protocol (IGMP) to manage the exchange of identity information between multicast gateways and multicast machines.
Therefore, it is more appropriate to adopt multipoint communication in point-to-multipoint communication when designing the system. In teaching, teachers should first apply for a multicast group address (fixed or temporary) on the Internet, then join the students in the "virtual classroom" to log in, the teacher counts the list of members, sends the applied multicast group address to the students, and the teachers and students send messages through multicast.
Transmission of multimedia data
Another important problem of this system is how to solve the transmission of multimedia data. Dynamic video data and voice data need to be transmitted in the system. First of all, how to transmit them in real time is the key of this system workbench. Generally, due to the large amount of uncompressed audio and video data, in order to transmit multimedia data in real time, it is necessary to compress audio and video data in addition to the network transmission speed. On the one hand, compression reduces the storage capacity of audio, images and sports videos, on the other hand, compression reduces the bit rate necessary to transmit these data on the network.
ISO/MPEG is a moving video compression standard. This standard not only uses the information redundancy of each frame of data, but also uses the information redundancy between frames. The compression ratio is very high, the maximum is 100: 1, and the average is 50: 1. In addition, CCITT H.26 1 is the standard of International Telegraph and Telephone Advisory Committee, which is used to provide video compression and decompression in videophone and video conference. CCITT G.722 is a standard for audio compression and decompression in videophone and video conference. With these compression standards, it is possible to transmit multimedia data on the Internet.
The working principle of the system (taking the distance education system of Xi Jiaotong University as an example)
Teachers install two or three cameras with pan/tilt, video capture cards, computers, microphones and speakers in the multimedia electronic classroom. The on-site teaching situation (video and audio data) is obtained through the video acquisition card in the multimedia communication server (also known as Producer). These data are converted into the Real Video format of real-time multimedia data stream by Real Producer plus G2 software (from Real Network Company) and transmitted to the G2 server of Real Server (SUN E3500) located in the distance education center. On the one hand, it is directly played by the real server server; On the other hand, it is stored in the form of a file (*) on the server. rm)。
After using ordinary multimedia PC and installing the client browser software of Real Player G2, client users can receive real-time online demonstration teaching through campus network or Internet network. Then install a video head to capture students' images, so that teachers can observe students' lectures conveniently; The earphone is used for receiving the teacher's voice; Microphones are used to collect and transmit students' voices.
Real Server G2 Media Playback Server uses Real Server G2 software, which can automatically provide image compression quality from 28.8K and 56K modems to high-speed LAN according to users' network bandwidth.
Users use ordinary multimedia PC to access the campus network through dial-up or private line. As long as the Real Player G2 client software is installed, they can query and order the video services provided by this system through WWW browsing.
5. Concluding remarks
At present, the State Education Commission also pays special attention to the development of distance education in China. With the pilot work meeting held in the Ministry of Education on June 2 1 day, the project of "Training Mode Reform and Open Education Pilot of China Central Radio and TV University" was officially launched. The pilot project is an important part of the Ministry of Education's plan of action to revitalize education for the 2 1 century and the modern distance education project. It is also an important measure for the Ministry of Education to reform the talent training mode of higher education and develop modern distance open education, which has opened a new curtain for the development of distance education in China. Understanding the current development status and existing problems of distance education in China can make joint efforts to contribute to the cause of distance education and make the level of distance education in China enter the ranks of developed countries as soon as possible. This is the purpose of this article.