Video on demand and interactive TV

The concept of video-on-demand and interactive television

The interactive TV ITV (Interactive TV) system is a new form of information service in recent years, it has increased the interactive ability for the ordinary TV set, so that people can obtain various network services according to their own needs, including video service, digital library service, multimedia information service and so on.

At the same time, the name of video-on-demand VOD (video on Demand) appears more and more in the media. For video on demand, the following definition has a certain representativeness: "The user selected programs, through the communication network transmission, distribution to the user terminal equipment." "Although this service looks familiar, it can be explained by the distribution of information through the communications network, but there are a lot of deep problems hidden" video on demand can be described as an entertainment service, interactive. Since ITV and VOD are interactive, then ITV and VOD between the end is what kind of relationship? The telecommunications sector and the broadcasting sector are currently engaged in the development of interactive video services, which, by convention, have a two-way high-bandwidth Fibre Channel, while the broadcasting department has been operating video business for a long time and has a large number of one-way High-bandwidth cable video lines. The advantage of the telecommunications sector is the existing Fibre Channel, but the Subscriber access line is still twisted, bandwidth is not enough, the solution is to use asymmetric digital subscriber line ADSL, radio and television as a traditional video provider, the advantage is that the coaxial line has been laid to the user's home, can provide high-bandwidth user access, but the one-way path needs to be reformed. From the provision of video services, the telecommunications sector and radio and television departments are both collaborators and competitors. This competitive situation resulted in the creation of two system names for interactive video services. From the point of view of radio and television, the interactive video service is regarded as a TV system, called Interactive TV ITV, the user's terminal is a television, plus an interactive device called a set-top box. If from the telecommunications point of view, the interactive video service as a business, called Video-on-demand VOD, the user terminal can be either a TV plus set-top box, can also be a personal computer.

Whether they are interactive or video-on-demand, they provide interactive video services to users. One emphasizes the client side and the other emphasizes the system service side. It is worth mentioning that these two names are often mixed with each other.

The architecture of the VOD is shown in Figure 1. VOD system consists of video service provider, transmission network and user terminal. Video service providers provide video sources and the management of their video service systems, which are typically composed of video servers, secondary storage servers, accounting computers, and program selection computers, as shown in Figure 2. The video server stores the video source online, and the secondary storage server stores the backup large-capacity video library. When the user's on-demand video data is not in the video server, the backup video needs to be transferred from the secondary storage server to the online video server. program computer and accounting computer can be a computer, in the small VOD/ITV system can also share a computer with the video server, they assume the video server and users between the session management and VOD/ITV system service management. The user terminal is the interface that VOD/ITV provides service to the user, the typical terminal device is a set-top box or personal computer. The transport network provides downlink video streaming, uplink commands, and routing requests. The common way of user access network is to use UTP Access ADSL subscriber line, coaxial cable connected modem, fiber coaxial cable mixed HFC access or fiber user loop FTTC (FTTB) access.

At present, the main applications of interactive video services are as follows: Movie on demand, interactive TV news, directory browsing, distance learning, interactive advertising, interactive video games.

II. structure of video-on-demand/interactive TV system

VOD/Interactive TV system is a distributed multimedia system, it is a media server and network switch multi-level structure, in this system, multimedia data to be compressed, stored, retrieved, and transmitted through the network to the destination, and then decompression, and on the receiving device synchronized studio.

Third, concluding remarks

----at present, video-on-demand/interactive TV system is still in the experimental stage. Many computer companies and research institutions at home and abroad design and develop a variety of servers, set-top boxes and other VOD/ITV key equipment, the various forms of interactive service prototype research, The information access mode in the new design and experiment prototype can provide the interface of browser form in the Internet and the VOD interface based on content retrieval, making it easier and more convenient to access the large-scale video information. The introduction of these VOD/ITV products and experiments with prototype systems have led people to see that in the near future video-on-demand/interactive television systems will be as ubiquitous as telephones and televisions, and that people will get more convenient and richer services through the interaction of information.