【 Weak current College 】 what is video on demand (VOD) technology---Power By 【 China power house network 】

VOD (Video on Demand) is short for VOD technology, also known as interactive TV on demand system, that is based on user needs and plays an appropriate video programs, and fundamentally changed users past passive watching TV. When you turn on the TV, you can not see advertising, not in a hurry for a programme at any time directly on-demand content, watch the hope is like playing just put in your own home video recorders or VCD machines of a new film, but you do not need to purchase a video or VCD disk, or video recorders or VCD. This is information technology brings to your dreams, it through multimedia network video programs according to personal wishes sent to millions of households.
Looking to the application of broadband networks, VOD is most relevant to people's life, but it's also the most technically difficult. With China Telecom, is a high-speed roads, it is necessary to have a car race, the VOD application is broadband multimedia networks's most eye-catching cars.
VOD technology not only can be applied in Telecom's broadband network, also can be applied in the community, local area network and cable television and broadband networks. Now in the process of building intelligent community, computer network cabling has become an essential part of that community users can use computers, television sets (with set-top boxes), for VOD applications, rich cultural life of the people; cable television through two-way transformation, you can let our TV users through cable television network on-demand video programming. As a VOD system is mainly composed of three parts: the service-side system
Service-side system is mainly composed of video servers, document management server, internal communication subsystem and the network interface. Archives management server is mainly responsible for user information management, billing, and television materials, finishing and security tasks. Internal communications subsystem for the main server room information delivery, background video materials and data exchange. The main achievement of the network interface with external network data exchange and provide user access to the interface. Video server mainly consists of storage, caching and control management modules, with the goal of achieving media data compression and storage, as well as by request media information retrieval and transmission. Video server and traditional data server there are many significant differences, the need to increase the number of dedicated hardware and software features to support the special needs of the business. 　　For example: media data retrieval, real time transmission of the information flow and information encryption and decryption. For interactive VOD system, the service-side systems also need to implement the user real-time request processing, access, admission control, VCR (Video Cassette Recorder) features (e.g., fast forward, pause, rewind, etc.) of the simulation. Network system
Network system consists of backbone network and local network in two parts. Because it is responsible for transmitting video stream, so is the impact of continuous media network service system performance is critical. At the same time, the media service system of the network portion of the investment is enormous, so the design time not only to consider the current media application on high bandwidth needs, but also to consider the future development needs and backward compatibility. 　At present, can be used to establish this service system of network physical media mainly: CATV (cable TV), coaxial cable, fiber optic and twisted-pair cable. While the use of network technology is: Fast Ethernet, FDDI and ATM technology. Client system
At present, according to different functional requirements and scenarios, there are three main VOD system: NVOD, TVOD and IVOD.
NVOD (Near-Video-On-Demand), you can refer to it as near-on-demand television. This on-demand TV by multiple video streams, interval time to startsending the same content. For example, twelve video stream every ten minutes to start a send the same two-hour TV programmes. If users want to watch this TV show may need to wait for the longest, but will not exceed ten minutes, they will choose from one of their recent time starting point for watching. In this way, a video stream may be shared by many users.
TVOD (True Video-On-Demand), referred to as true on-demand TV, it really support the click-and-drop. When a user request, video server will immediately transmit user want video content. If another user is made the same demand, video server will start immediately for him to another transport the same content as the video stream. However, once the video starts playing, continuous play until the end. This way, each video transfer service for a user.
IVOD (Interactive Video-On-Demand), called interactive on-demand television. It is larger than the first two methods have greatly improved. It not only supports the click-and-drop, but also allows the user to the video stream for interactive control. At this point, users can elephants do traditional VCR, the implementation of programmes of the play, pause, rewind, fast forward and automatic search, etc.
Only use the appropriate terminal device, the user only with certain services or service providers linked and interoperable. In VOD system, television sets and set-top boxes (Set-top Box), and in some special system, you may also need a computer equipped with a large capacity hard drives in your computer to store the video from the video server. The client system, in addition to the hardware device involved, but also with related software. For example, in order to meet user demand for multimedia interactive, must be on the client system's interface to transformation. In addition, in continuous media, the media stream buffer management, audio and video data synchronization, network outages and disruptions of coordination in the Studio and other issues need to befully taken into account.
Visible for VOD services, although very tempting, but its implementation is not a root "easy to chew on bones". But as the network technology, computer technology, storage, technology, the rapid development of the vast number of users to fully enjoy the VOD pleasure day has notFar away. By that time, on-demand remote control, a user simply do a slight press, can be true of the watch and enjoy their favorite programs, and may at any time adjust the show progress, speed, etc. The emergence of VOD allows TV becomes a random access to information media, more like a book or a newspaper, you can browse, you can adjust, no longer limited to a particular time, date, and retention programs.
Although, there is initially of VOD in order to better meet users ' needs to watch the video programs, but as VOD technology continues to progress, its wide range of applications on popular culture and business model will have a strong impact. VOD can not only as an end user provides diversified media information flow, to expand people's information channels, rich people's spiritual life; and in hospitals, hotels, aircraft and other places of entertainment, staff training, long distance market investigation, the company's advertising business, and other areas will be gradually filled with VOD technology, new applications.