What is video-on-demand (VOD) technology

What is video-on-demand (VOD) technology

VOD (Video on Demand) is the abbreviation of VOD technology, also known as interactive VOD system, meaning that according to the needs of users to play the corresponding video program, fundamentally changed the user in the past passive watch TV deficiencies. When you turn on the TV, you can not see ads, not for a program in a hurry, at any time directly on demand to watch the content, like playing just put into their own home VCR or VCD machine in a new film, but you do not need to buy video or VCD disc, also do not need a VCR or VCD machine. This is the dream that information technology brings to you, which delivers video programs to millions of people on a personal basis through multimedia networks.

Look at the application of broadband network, VOD most close to the people's lives, but its technical difficulty is also the largest. Take the words of China Telecom, that is, high-speed road, there will be a car run, VOD application is the most eye-catching broadband multimedia network car.

VOD technology can be used not only in the broadband network of telecommunication, but also in the broadband network of LAN and cable TV in the community. Now in the construction of intelligent community, computer network wiring has become an indispensable link, community users can through the computer, television (with set-top boxes) and other ways to achieve VOD video-on-demand applications, enrich the cultural life of people; CATV has been transformed in two directions, Can let the vast number of TV users through the cable TV network on demand video programs.

As a VOD system is mainly composed of three parts:

Service-side system

The service-side system is mainly composed of video server, file Management Server, internal communication subsystem and network interface. The file Management Server mainly undertakes the tasks of user information management, billing, film and television material collation and security secrecy. The internal communication subsystem mainly completes the transmission of information between servers, the exchange of backstage film material and data. The network interface mainly realizes the data exchange with the external network and provides the user access interface. The video server consists of storage device, cache and control management unit, whose goal is to compress and store the media data, and to retrieve and transmit the media information according to the request. Video server and traditional data server have many significant differences, need to add a lot of dedicated hardware and software functional equipment to support the special needs of the business. For example: Media data retrieval, real-time transmission of information flow, as well as the encryption and decryption of messages. For the interactive VOD system, the service-side system also needs to implement the real-time request processing, access permission control, VCR (video Cassette Recorder) function (such as fast forward, pause, redo, etc.) simulation.

Network system

The network system includes two parts, backbone network and local network. Because it is responsible for the real-time transmission of video information flow, it is a critical part of the performance of the Continuous Media Network Service system. At the same time, the network part of the media service system invests greatly, so we should not only consider the demand of the current media application to the high bandwidth, but also consider the need of the future development and the backward compatibility. At present, the network physical media that can be used to establish this kind of service system are mainly: CATV (CATV) coaxial cable, optical fiber and twisted pair cable. And the network technology is mainly: Fast Ethernet, FDDI and ATM technology.

Client system

At present, according to different functional requirements and application scenarios, there are mainly three kinds of VOD systems: Nvod,tvod,ivod.

NVOD (Near-video-on-demand), can be called as the nearest-type on-demand TV. The way to do this on-demand TV is that multiple video streams start sending the same content in a certain time interval. For example, 12 video streams start a TV show that sends the same two hours every 10 minutes. If the user wants to watch the TV show, it may need to wait, but it will not last more than 10 minutes, and they will choose to watch it from their most recent point in time. In this way, a video stream can be shared by many users.

TVoD (True video-on-demand), which is called real-on-demand TV, really supports point-and-place. When the user makes a request, the video server will immediately send the video content that the user wants. If another user made the same request, the video server would immediately start another video stream for him to transmit the same content. However, once the video stream begins to play, it will continue to play continuously until the end. In this way, each video stream is converted to a user service.

Ivod (Interactive video-on-demand), called Interactive on-demand TV. It is a great improvement over the first two ways. It can not only support point and place, but also allow users to interactively control the video stream. At this time, the user can be like operating a traditional video recorder, to achieve program playback, pause, rewind, fast forward and automatic search.

Only by using the appropriate terminal equipment can users contact and interoperate with a service or service provider. In VOD systems, televisions and set-top boxes (set-top box) are required, and in some special systems, a computer with a large-capacity hard disk may also be needed to store video files from the server. In the client system, in addition to the corresponding hardware equipment, also need to be equipped with relevant software. For example, in order to meet the needs of multimedia interaction, the interface of client system must be reformed. In addition, in the continuous media playback, the media stream buffer management, audio and video data synchronization, network interruption and broadcast interrupt coordination and other issues need to be fully considered.

It can be seen that VOD service although very tempting, but its implementation technology is not a "easy to chew bones." However, with the rapid development of network technology, computer technology, storage technologies and so on, the majority of users enjoy the VOD fun day is not far away. At that time, on-demand users as long as the remote control, a little press, you can do to watch and enjoy their favorite programs, and can adjust the progress of the show at any time, speed and so on. The advent of VOD has made the television a kind of random access to information media, more like a book or a newspaper, can browse, can adjust, no longer limited to a certain time, date and fixed program restrictions.

Although, Vod's initial appearance is in order to better satisfy the user to watch the video program's demand, but along with the VOD technology unceasing progress, its widespread application to the popular culture and the commercial operation mode will have the strong influence. VOD can not only provide the end users with a variety of media information flow, to enlarge people's information channels, enrich people's spiritual life, and in hospitals, hotels, aircraft and other places of entertainment, the company's staff training, long-distance market research, the company's advertising business and other fields will gradually fill the new application of VOD technology.