The application of Video server network in Broadcasting System

I. System requirements and equipment selection

At present, with the rapid development of computer high-speed network and multimedia storage technology, the TV broadcast field is in a period of change from tape broadcasting to hard disk broadcasting. Video network Broadcasting system centered on hard disk storage as a new technology has been widely concerned in the radio and television industry.

At present, most of the hard disk broadcast systems developed by some TV stations are mainly prepared by two video servers. The main advantages of this method are simple structure and high reliability. But its shortcomings are also more obvious. One is because it takes the main, standby (also known as mirroring), make the system the same program material storage needs two copies, the actual storage efficiency can only reach about 45%, improve the cost; Secondly, the system expansion capacity is limited, the system expansion, due to the number of disk array limit, storage time can not be too long, three is the main, Standby machine because the encoder can not be shared, the need to double the codec, higher cost. On the basis of the research on various hard disk video servers in the world, we choose the BMC1200 Video server network system produced by American Sea-change Company according to the actual situation in Taiwan. This system adopts a new technical scheme-mediacluster technology. It is a network cluster consisting of 3 or more video servers, and adopts MPEG-2 coding compression, which is characterized as follows:

1, multiple video servers using network connectivity, through the reference Mediacluster core technology, to achieve multi-level fault recovery function. It not only uses the RAID5 redundancy technology between the disk arrays in each server, but also realizes the data protection by using the parity characteristic of the data block. Moreover, the RAID2 technology is applied again between each two video servers, and the system has a level two security guarantee. Not only can ensure that all video/audio data will not be lost because of a group of hard disk damage, even when any one of the video server failure, but also through the rest of the server commander of the operation of data, the loss of data to recover without loss. At the same time, because the video server network has two level raid protection, makes the same program material storage in the system only one copy, under the same storage capacity, the hard disk effective broadcast capacity can reach about 70%.

2, Sea-change using its own patented technology, in the video digital network platform to establish a seanet protocol to achieve it in the server between the use of RAID2 technology, so that after the compressed view/ When the audio data is split into blocks, the data is stored evenly in the disk array of each server in a constant bit stream mode, and the network is balanced when the data is transferred between the servers, which can obtain the effective bandwidth of nearly 80%, thus solving the network conflict and blocking defects. At the same time, because of the use of video network structure, the program material can realize multi-channel broadcast full sharing, the system expansion is also very convenient.

3, multiple input/output video/audio interface, input encoder can be shared, the number of channels and functions can be flexible configuration.

4, each server UPS power supply for other servers to share the use, and allow hot plug, improve the reliability of the system.

Second, the hard disk video server network Broadcast system

Of the system's main devices, we have three video servers (three nodes below). Each node contains 12 18GB hard drives, and if the 12MB/S code stream is used, the effective storage time is 64 hours. Each node is equipped with a three-way video/audio decoder board and a coding board, a total of 12 channels of video/audio input and output channel.

Three nodes are connected through the built-in four-port IOP-914 100Mbps network card 22 respectively to form a bidirectional non-blocking video network topology, which is used to evenly access and transmit video/audio digital signals with 80Mbps code flow. And because each node is connected with other nodes in the network, even if there is a link failure, the Network fault recovery function can still ensure the smooth network.

Boss Broadcast Server Management station and three nodes through a hub HUB1 composed of hard disk server network management, detection system, and through the management interface at any time dynamically display the working state of the hard disk system, for broadcast personnel monitoring. At the same time, the user interface and alarm system of fault diagnosis are provided to diagnose the fault of each hardware in the network. In addition, broadcast control and material file management system is composed of two main, the standby database server is composed of two main, standby and two main, standby and two upload workstations through network hub HUB2 to form a 100mb/s Ethernet, which is used to transmit program information files and broadcast program tables, etc. constitute a complete network broadcast control system.

This shows that the network characteristics of the system is the use of two-tier network structure, the purpose of which is to make the video/audio bit stream and the program file information data in different network environment, to ensure the security of digital and data signal transmission, and the two coordinate to complete the broadcast work. Third, system design and application

My hard disk automatic broadcast system design considerations are mainly around the completion of the television channel and the other two channels of advertising spots to design. The hard disk system control software is developed by using the Louth BMC1200 hard Drive Control protocol of the Sea-change company, and the control interface uses RS-422 serial interface communication. The database platform of material file management is developed by using DELPHI4.0 programming language and VC + + under the environment of WINDOWSNT4.0 Chinese version network operating system. The main application of this system has the following three aspects.

1. Complete the TV channel anchor

We have considered the demand and characteristics of TV program broadcast, the program broadcast type is more abundant, the advertisement broadcast task is heavy. Because of the high replay rate of programs and advertisements, it is very suitable to use video server as the anchor device. Design considerations and major hardware configurations are as follows. 1 broadcast control and management.

In order to ensure high reliability, the design of broadcasting system should consider the redundancy fully. As shown in Figure 1, the system on the one hand configured two channels of video channel hard disk, and choose between the different nodes, the main, prepared, on the other hand, broadcast control PC also uses two completely master, prepared the design mode.

The main and standby stations use the CCTV's field inverse standard Time signal as the time datum, according to the agreed agreement to control the two hard drive decoding channel synchronously to broadcast, and separately with the Broadcast control center synchronous signal Lock, causes two channels to broadcast the signal picture to be exact. Realize hot backup of dual broadcast system.

Primary and standby broadcast station before starting the broadcast channel, through the LAN with the database server for a connection, the server stored in the latest Broadcast program table and file data into the local broadcast station. Once the primary and standby broadcasting station is on the air, it is automatically disconnected from the network, and any anomalies in the network will not affect the normal broadcast control. When there is a problem with the main road broadcast station or decoding channel, even if the main road decoder board in the 0-node server is completely not working (such as Down machine), due to the specificity of the hard disk video network, located in another node of the standby channel can still work, you can immediately through the broadcast control matrix two Select a switch switch to the standby channel to continue playing, Ensure the uninterrupted nature of the broadcast.

Broadcast station in the control of the hard disk DDR broadcast, but also in accordance with the need to control the VCR VTR to play, in case of emergency, such as the hard drive channel problems or too late to broadcast the program input to the hard disk, you can quickly broadcast station directly control the video recorder VTR play. This kind of disk belt mixed broadcast way is more flexible, adapts the broadcast first line the demand.

2 Primary and Standby database server.

The primary and standby domain database server is equipped with a network database (SYBASE), which consists of numerous data models. Mainly has the material description information, the Broadcast Program table data record, after sowing information record and so on. If the primary domain server fails, the system automatically switches to the standby domain and starts the standby domain server, which does not affect the performance of the program recording and broadcasting.

3 program upload Workstation.

As shown in Figure 1, according to the BMC1200 hard disk server video/audio channel system considerations, we will 0 nodes and a node of the coding channel for television channel program upload. The upload workstation can simultaneously control two channel coding channels and two video recorders, including the use of TC time code to set the tape into/out point, automatic find points, playback, recording and stop input. Its function is the video signal output from the recorder through the encoding channel to the hard disk, and can automatically fill in the material upload time and date.

Upload Workstation application of open database programming interface, through LAN LAN to the relevant program identification management information files and broadcast information into the main, standby domain database server, set up a complete Windows NT online SQL database Management Server system. The contents of a database or material library can be added or deleted at any time by means of a data file table. Upload station can also input the content of the material to monitor or edit, can also real-time display in time units of the remaining storage space, so that operators can monitor the use of disk space. Another function of uploading workstations is to complete the production of the broadcast listings. In order to find the related programs in the program information database according to the sequential sequence of the series, a new Broadcast program table is made, and the sequential program start time is automatically completed according to the length information of the data.

The upload workstation can also complete the upload pre-monitoring function through the hard drive output channel. Using the software to establish a fast portals can be broadcast program of the last 20 seconds of the content of each footage of the pre-broadcast detection, in order to check the hard disk input material is correct, to ensure that the broadcast safe and reliable.

HDD Server program upload selected two Sony company Betacam VCR, channel video signal using digital component serial interface SDI, audio signal using embedded mode. In order to be compatible with the existing Utah matrix Analog Composite Signal interface, the hard disk broadcast channel adopts the standard analog interface provided by BMC1200 video server.