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Zhou Yongjia Beijing University of Technology Beijing 100124
Abstract: Multimedia teaching, as an infrastructure and an important part of computer-aided teaching, has been widely used in classroom teaching in colleges and universities. Among them, network-based video and audio on demand has become an important technology for multimedia teaching in schools. How to effectively use multimedia Recording and broadcasting classroom equipment to make it more effective has always been a problem that colleges and universities are trying to solve. This article introduces the system and applications of recording and broadcasting classrooms in order to promote the application and management of recording and broadcasting classrooms to become more reasonable and effective. economic.
Keywords: recording and broadcasting classroom system application
At present, with the increasing popularity of the network, network-based video and audio on demand has become an important demand for multimedia teaching applications in schools. At the same time, the penetration of multimedia courseware in the teaching process is getting deeper and deeper. In addition to recording the image and sound of the instructor in the teaching process, the classroom recording also needs to record the content of the multimedia courseware simultaneously, and can quickly and conveniently generate courseware for live broadcast through the network in real time. This requires powerful recording and broadcasting classrooms to play a decisive role in teaching.
1. System configuration
The construction of recording and broadcasting classrooms can realize multi-angle, all-round classroom recording and real-time live broadcast of the teaching process. The recorded content includes not only the scenes of teachers and students teaching and listening, but also the content of courseware used by teachers to lecture. The system has MPEG2, MPEG4 dual stream transmission; MPEG4 compression card completes the MPEG4 format encoding of low stream, which can realize the live broadcast of the teaching site; MPEG2 acquisition card can collect high quality and save it in the dual stream acquisition broadcast server In the middle, it can be made into a high-quality DVD, and the material can also be transferred to a non-editing server through the network for editing and making into excellent courseware for later on-demand.
According to the different functions realized, it is mainly divided into 4 parts:
1. Traditional multimedia classroom
The parts of the traditional multimedia classroom mainly include: multimedia teaching equipment, network central controller, projection display, power amplifier, IP telephone, classroom audio and video return and other parts.
2. Audio and video signal acquisition and control
A video conversion card is used to convert the VGA signal of the teacher's computer / notebook into a composite VIDEO signal / S terminal video signal, which is connected to the stunt station as an information source for editing.
The camera considers that the scene needs to be configured with a 16x zoom lens. The main camera position is installed opposite the podium to shoot the panorama of the teacher's lecture; the two auxiliary camera positions are installed in the middle of the side walls on both sides, mainly used to shoot the teacher. Close-up shots and students' lecture screens.
The cloud mirror controller is equipped with a video interface board to realize remote operation of the three cameras and the cloud platform in each classroom. The student's voice is collected by a suspended microphone. Each classroom is equipped with 6 unidirectional condenser microphones with a collection angle of 120 °.
3. On-site editing section
It mainly implements on-site editing of live classroom teaching scenes, mainly including mixers, stunts and monitors.
All the audio signals on the scene are connected to the mixer, which is convenient for the control of the audio system signals.
Three cameras, teacher courseware videos, mixer audio are connected to the special effects station, audio and video switching and special effects production, and the initial cut work at the teaching site.
Real-time editing of the teaching situation through the analog component interface of the stunt station into the dual stream acquisition and broadcast server's MPEG2 capture card for high-quality collection, the material is temporarily stored in the server or transmitted to the editing storage server via Ethernet for post-editing.
The real-time edited teaching live video enters the MPEG4 compression card of the dual stream acquisition and broadcast server through the composite video of the stunt station, performs MPEG4 encoding of the low bitstream, and performs live webcast of classroom teaching live.
4. Dual stream live video part
The system has MPEG2, MPEG4 dual stream transmission, storage network, each live room has an independent upload server (collection broadcast server), the total storage capacity of 4T. The MPEG4 format is available for live webcast.
The dual stream collection and broadcast server receives the data of the analog component interface of the video and audio switcher through the broadcast-grade MPEG2 compression card, and performs high-quality collection. The material is temporarily stored in the server, and then transmitted to the fiber storage array of the editing storage server through the campus network. Post-editing; At the same time, the dual-stream acquisition and broadcast server receives the data of the composite video interface of the stunt station through the MPEG4 acquisition card or H.264 encoding card, and performs the MPEG4 encoding of the low-stream to realize the live webcast of the classroom teaching live.
(1) Live teaching part
The start and stop operations of live broadcast and recording are controlled remotely through the IE browser, and the release management of live broadcast resources can be performed remotely, providing real-time video live streaming services with smooth pictures, clear sound quality, and low latency under the network environment. The use of advanced MPEG4 / H.264 codec technology not only ensures the quality of the image, but also greatly reduces the bandwidth occupied by the video, does not affect other uses of the network, and realizes real-time and efficient compressed audio and video streaming live webcast.
(2) Storage and editing
The editing system is completed by the existing non-editing workstations in the school. It mainly receives high-quality MPEG2 data from the collection server through the network and stores it in the disk array. The system provides administrators with simple and convenient control and management of all software and hardware resources. This part is at the core of the network video resource management system. The post-editing and packaging of the saved MPEG2 files are made into excellent courseware.
(3) Network structure
The entire dual-stream video live broadcast system is based on the Gigabit Ethernet structure. It takes advantage of the simple structure of the Ethernet network and the widely supported protocols. It applies this mature technology of the Ethernet network to the new generation of DV networks. The dual-stream broadcast acquisition servers of the 3 classrooms have 2 gigabit ports, one gigabit port is connected to the campus network, and the other gigabit port is connected to the dual-stream live network system.
2. System Application
1. Breakthrough in teaching methods
The modern information society needs talents with versatile knowledge and extensive knowledge. A large number of dull and boring texts on blackboards and blackboards cannot arouse students 'enthusiasm and trigger students' thinking. The use of multimedia teaching, text plus sound, pictures, dynamic images, active classroom, showing in front of students, immersive, not only helps students understand, but also develop students' thinking. For example: engineering teachers can hardly describe the principles of mechanics and mechanics in language. On-demand broadcast of the prepared video materials during class will make students suddenly open; language teachers can wander among students at any time and form effective interactions with students ; Art teachers can move the creative place to the center of the classroom, and close the distance with classmates to facilitate communication between teachers and students.
2. Expansion of teaching space
The teaching and learning space of traditional teaching teachers and students is limited to one classroom, and the source of students' knowledge is very limited. Using the Internet to broadcast teachers' classes, one is convenient for students to take classes, and then reduces unnecessary repetitive teaching by teachers. Courses and instructional lectures that are particularly popular with students can also be transmitted to remote classrooms via wide area networks. At the same time, the courses can also be stored for students to study at any place on the Internet. School leaders can also check teacher lectures at any time. For example, there are more people in joint classes and academic reports. A classroom often cannot solve the problem. The recording and broadcasting classroom can be used to watch in any multimedia classroom.
3. Flexible teaching time and open choice of teachers and students
In traditional teaching, there are curriculum arrangements, and students take classes at designated locations within their time. When students choose multiple subjects, once the time conflicts between the courses cannot be both. For example, the teacher ’s lectures are recorded and stored on the server, and the students can order them at any time after class, so that the students have their own schedules, which is also convenient for students to review after class. After the teachers and students break the constraints of space and time, the free choice between teachers and students brings a lot of space. Students are completely free to choose their favorite teachers. Schools can choose teachers that are popular with students, and the quality of teaching can be greatly improved. For example, the three national-level excellent courses in mechanical design, probability and mathematical statistics, and material mechanics of our school have been broadcast live online. Students can watch it through the campus network at any time, and the number of clicks has reached nearly 8,000.
4. Reduce the cost of making teaching courseware
Before the construction of the recording and broadcasting classroom, two video teachers were required to collect audio and video in the early stage of a fine course, and a non-linear editing was required in the later stage with a director teacher and courseware. The cumulative time for producing a fine course was as long as 5 to 7 hours . After the recording and broadcasting classroom is completed, only one instructor teacher needs audio and video processing in real time and one teacher for real-time recording in the early stage of a fine class, and only one editor instructor needs to perform simple editing in the later stage to produce a high-quality class. The time is only about 2 hours, and the time cost is greatly reduced.
In short, with the development of education, the advancement of science and technology and the improvement of teachers ’application of modern technology, multimedia teaching methods will be popularized in colleges and universities. The recording and broadcasting classroom system has entered the modern multimedia teaching classroom with its comprehensive functions and unique features. Many functions of the multimedia teaching equipment are realized, and the ordinary classroom is upgraded to a real-time interactive teaching environment of audiovisual, graphic and text, which makes it easier for students to understand acceptance and improve the teaching effect. The development of recording and broadcasting classroom system makes multimedia classroom management more scientific and efficient, has broad application prospects, and will play an increasingly important role in the construction of modern college education.
References [1] Geng Jianmin. Design principles and configuration schemes of online live classrooms [J]. China Educational Technology Equipment, 2003, 12
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