Video on-demand system and technology

With the development of multimedia technology, communication technology and hardware storage technology, people are no longer satisfied with the former single and passive information access, but want to participate in the program actively. Video-on-demand (video on Demand,vod) is a kind of interactive business, which causes the cable television industry and the communication industry to attach great importance.

Interactive VOD system consists of front-end processing system, broadband switching network, user access network, user terminal equipment (set-top box plus TV or plus computer). VOD system can not only adopt centralized processing structure, but also can use centralized management, distributed processing mode, and flexible selection of HFC, FTTB, FTTCADSL, VDSL and other access methods, user set-top box can be used in accordance with the access mode matching interface, through the television, PC video/audio/ The display and communication of data.

First, the user through their own VOD terminal, to the nearest VOD business connect eight points to initiate the first communication call, request the use of VOD business, through the VOD business uplink (such as computer networks, telecommunications network, cable television network, etc.) to the current frequency server to send a request; The system responds quickly and displays on-demand orders on the user's TV screen , and the user information audit, determine the identity of the user, the user according to the demand list to make a choice, request to play a program, the system according to the audit results, decide whether to provide the corresponding services. Play the requested program within a short interval of time to the specified device and be ready to respond to the new request.

First, front-end processing system

The front-end processing system is generally composed of video server, disk array, program database, broadcast control system and so on. The high speed data transmission capability of the video server ensures the user's near-instant access to a large number of videos, video programs, games, business information and other services. Its outstanding advantage is that several users can watch the same program from different time starting point, avoid the wonderful program is exclusive by a user, or after a user sowing point, other users can only passively follow the situation, this for the user on demand for relatively centralized field will be particularly suitable.

The VOD video server holds a large number of compressed image programs and can provide users with the necessary copy of the program through the network, or it can include real-time MFEG encoder to access live broadcast. Program database is an archival system, save a large number of compressed form of the film program, can be downloaded to the video server in batches. VOD video server through direct with the user, real-time two-way interaction to control the play of the program, including the selection of the program, the start and end of the playback process, the control of playback speed and the dynamic switching between different programs, VOD video server must run the corresponding software to coordinate the various actions, while providing a friendly user interface. It should have the following characteristics:

(1) capable of storing at least hundreds of hours of video programming.

(2) If a user to VOD server random dynamic access is called the session process, then the VOD server must be able to support thousands of simultaneous and mutually independent "session" process.

(3) A set of encryption and user access control mechanism to prevent illegal user access.

As the core of VOD system, the performance of VOD video server directly determines the overall performance of the system. In order to respond to the service requirements of multiple users at the same time, the video server usually uses the time slice scheduling algorithm.

In order to be able to adapt to real-time, continuous and stable video streaming, the video server has large storage and high data rate, and it should have many functions such as admission Control, request processing, data retrieval, and so on to ensure that the user requests the effective service under the system resources. The storage device should have a SCSI interface to ensure the capability of high-speed, parallel, multiple I/O buses. Based on the ATM VOD system, the video server is a broadband video server centered on the multi-channel routing switch (MPSR). Servers of this structure can provide instant interactive video-on-demand (Interactivevod with instaneous access,ivod-i) and delayed interactive video-on-demand (Interactive VOD with delayed access Ivod -d) Two modes of service. When a large number of users on demand at the same time, the transfer rate of the server is very high, but also require other related devices can support this high transmission rate, this is difficult to achieve. To do this, you can set up a video buffer pool at the edge of the network, such as the ATM network front-end switch, the high demand rate of the program copied to the buffer pool, so that some users can only access the buffer pool, the buffer pool does not have to on-demand program, can go to the server, which reduces the burden on the server, and can increase as the user increased buffer pool. The load buffer pool is available 150mb/s rate, while the transfer of the program from the buffer pool to the user is 2mb/s rate, so that a server can support multiple users.

Second, control management system

The control management system is a signaling transmission network, which is used to manage the connection of user to VOD video server. Because the actual VOD system can have more than one VOD video server, therefore, the control management system uses two level gateway management, the first level in the digital broadband switching system and transmission system to achieve the choice of different channels; the second level completes the selection of a particular program on a VOD video server.

The specific process of VOD signaling and data flow is as follows:

(1) connecting the set-top box and accessing the population equipment through the pre-confidence order; The S3,VOD system is communicated to the user by the service list from the population;

(2) According to user requirements, the population selected the relevant video server, that is, connected to S4, and provide service element primer;

(3) The initialization of the S4 can be done by a set-top box or video server, and the service population provides routing information, and the server provides the program list;

(4) The user chooses the program from the programme and passes the signaling to the video server;

(5) Through the network operation of the program from the video server to the set-top box, that is, connected P1, if necessary, the program can be loaded from the video library to the current frequency server, that is, connected p;

(6) Other signaling channels S5, S6, S7 all serve the operation center of the monitoring, recording and so on.