Xi'an University of Posts and Telecommunications
Software development papers
RealSystem-based remote teaching system
Remote Teaching System Based on realsystem
System Overview
Department: Computer
Professional: Computer Electronic Information Science and Technology
Class: Electricity 0101
Developer Name: Xu Zhaoyuan
mentor:
Start time: October 2003 to XX Month
System Overview
1.1 Multimedia Remote Teaching Concept
The era of knowledge economy requires people to learn new knowledge, skills, can keep up with the pace of the times. Learning will become a process with each life. Online teaching broke through the traditional "face" teaching limit, providing a new way of scattering, resource sharing, broad and interactive teaching, and therefore widely attracted attention.
Multimedia remote teaching refers to the establishment of a virtual teaching environment using multimedia technology and network technology; through the teaching environment, far-end students can go online, not restricted by time and space, and obtain the same knowledge as students in school. .
No matter where you are, whether you are late or severe winter, no matter how your foundation is good, you can get the same good textbook and the same excellent teacher. This is the ideal online teaching of "the same big class" in the world. However, it is necessary to truly implement this ideal, it still needs multi-faceted trials, forming a stable and effective teaching method, reaching the accumulation of online teaching resources (question bank, evaluation), in order to bring the biggest learning effect for online students.
Traditional textbook (text), a small number of classroom teaching is linear, in this way, in nature, describe, deliver, perceive, and in terms of a linear model with a linear model. The learner re-constructs three-dimensional, cross, integrated knowledge system. This type of knowledge is improved, it is inefficient, not perfect. One possible way should be three-dimensional nonlinear variety of experiences based on hyperlink, multimedia textbooks.
Technical, the distance education system is a multimedia application system based on modern media technology. It passes the teacher's image, sound and e-learning to students through modern communication networks, and can use the image, sound of the students as needed. Rewire to the teacher, thereby simulating the teaching of school teaching; while also using existing network conditions to establish virtual classes and strengthen communication between students.
Summary, the advantage of distance education is that it has broken through the time limit, increasing the opportunity of learning, which is conducive to expanding the scale of teaching, improving teaching quality, and reducing teaching costs. Learners can use a rich teaching resource to learn in accordance with their own speed and way of their own convenient time. Therefore, the eyes of the circular development, the distance education will become the supplementation and expansion of school education, and will promote the education reform of the school.
1.2 Main form of multimedia remote teaching
The multimedia remote teaching system has two main points in the form: First, the multiMedia mode, the second is the on-command method. The characteristics of the multicast broadcast method are periodicity, and the second is hazy, it can be real-time, or it can be stored in advance. The feature of the on-demand is to first store the course content to the video server, and students can limit any of the courses in the broadcast server without time limit.
The view screen required by the broadcast mode is only related to the number of courses opened in the same time, and has nothing to do with the number of teaching points (accepted points). For a remote teaching system using a broadcast method, each stream corresponds to a course, and how many courses need to be opened at the same time, and how many compressed cards (compression software) are needed.
The view screen required for the on-demand mode is equal to the number of users at the same time. Therefore, the compression card (compression software) quality requires a decrease, and the number requires an increase.
1.3 Characteristics of multimedia remote teaching system L video online communication authenticity, instantity
l Online teaching management is convenient and fast and systematic
l At any time, anywhere, online exam
A multimedia remote teaching system should include five elements:
(1) Students and teachers are geographically separated, not facing face.
(2) Government education department qualified for educational institutions
(3) Due to modern communication and multimedia technology
(4) Provide two-way interaction function
(5) Students can class with anytime, anywhere.
1.4 streaming media overview
Streaming Media is an important basic technology for modern network transmission, which is critical to online broadcast of remote teaching systems.
Streaming media refers to the media output to send the program as a data package with a video transfer server, transferred to the network. When the user decompresses the data by decompressing the device, the program will be displayed as before sending.
A series of related packets of this process are "flow". The streaming media actually refers to a new media transfer method, not a new media. After the flow of media technology, people can directly enter the voice directly; if they want to see each other's appearance, expressions, as long as they have a camera, they can see the goods, click, click, explain And the image of the characters will jump out; more realistic image news will also appear.
Multimedia information such as transport / video on the network is currently mainly downloaded and streaming two programs. The A / V file is generally large, so the storage capacity required is also relatively large; at the same time, due to the limitations of network bandwidth, the download often takes a few minutes or even hours, so this processing method is also very large. When streaming, sound, image or animation, etc., based on the audio and video server, the user's computer is continuous, real-time transmission, the user does not have to wait until the entire file is downloaded, but only after a few seconds or dozens of startup time Watch can be viewed. When the audio of the base is played on the client, the remainder of the file will continue to download from the server in the background. Flow not only makes the startup delay twice, a hundred times shortening, but does not require too much cache capacity. Flow transmission avoids the shortcomings that users must wait for the entire file to download from the Internet to watch.
1.4.1 Foundation of streaming media transmission
Streaming is a continuous time base medium using streaming technology in Internet / intranet, such as audio, video, or multimedia files. Its key technology is streaming. Stream transmission definitions are wide, and now mainly refers to the technical general name of the network transmission medium. Its specific meaning is transmitted to the PC through the Internet. There are two ways to achieve streaming: real-time flow transmission and sequential flow transmission. In general, such as video is real-time broadcast, or using streaming media servers, or applies a real-time protocol such as RTSP, that is, streaming. If the HTTP server is used, the file is sent in sequence. Using that transmission method relies on your needs. Of course, the flow file also supports completely downloaded to the hard drive before playing.
1.4.2 Sequential streaming (Progressive Streaming)
That is, the user can download the online media while downloading the file, the user can watch the online media. At a given moment, the user can only watch the downloaded part, and cannot jump to the front part of the yet known, sequentially streaming is not real-time streaming. Adjustment according to the speed of the user connection during transmission. Since the standard HTTP server can send this form of file, it does not require other special protocols, which are often referred to as HTTP streaming. Sequential streaming is relatively suitable for high quality segment, such as a piece, a slice, and an advertisement. Since the document is not desirably downloaded, this method guarantees the final quality of the movie. This means that users must experience delay before watching, especially for slower connectivity. But it has a high quality of the video clip. Easy to manage. Disadvantages are not suitable for long fragments and videos with random access requirements. Not supported on-site broadcasting, strictly said that it is a market broadcast technology. 1.4.3 RealTime streaming
Real-time streaming refers to ensuring that the media signal bandwidth matches the network connection, so that the media can be seen in real time. Real-time flow is different from HTTP streaming, and he needs a dedicated streaming server and transport protocol. Real-time streaming is always real-time transmission, especially suitable for on-site events, but also supports random access, users can quickly forward or retreat to watch the front or later. In theory, the real-time stream can not stop, but in fact, cycle suspension may occur.
Real-time streaming must match the connection bandwidth, which means that the image quality is poor when the modem speed is connected. Moreover, since the information loss, the information is neglected, the network is crowded or problematic, and the video quality is poor. If you want to guarantee the quality of the video, sequential flow transmission may be better. Real-time streaming requires servers such as RealServer, Windows Media Server. These servers allow you to control more levels of control over the media, so system settings, management is more complicated than standard HTTP servers. Real-time streaming also requires special network protocols, such as RTSP (RealTime Streaming Protocol) or MMS (Microsoft Media Server). These protocols sometimes have problems when there is a firewall, causing users to see the real-time content of some locations.
1.4.4 streaming media playback
u unicast
A separate data channel needs to be created between the client and the media server, and each packet sent from one server can only be transmitted to a client, which is called unicast. Each user must send a separate query on the media server, while the media server must send each user to a copy of the data package. This huge redundancy first causes the server heavy burden, and the response takes a long time, even stops playback; the management also is forced to purchase hardware and bandwidth to ensure a certain quality of service.
u multicast
IP Multicast Technologies build a network with multicast capabilities, allowing routers to copy packets to multiple channels at a time. With multicast mode, a single server can simultaneously send continuous data streams simultaneously with tens of thousands of clients. The media server only needs to send a packet instead of multiple; all the requested client sharing the same packet. Information can be sent to the client of any address, reducing the total amount of packets transmitted on the network. Network utilization efficiency is greatly improved, and the cost is greatly reduced.
u Dog and broadcast
On-demand connection is a proactive connection between the client and the server. In the on-demand connection, the user initializes the client connection by selecting a content item. Users can start, stop, back, fast forward, or pause flow. On-demand connections provide maximum control of convection, but this way is quickly used throughout the network bandwidth due to each client connected to the server.
