Network Express: Video Server Features and Highlights

    With the popularization of the Internet and the improvement of the network environment, network video surveillance has developed rapidly. Network monitoring has become a development trend in the security industry. For network video surveillance, the video server is an important part of the entire system and provides the core hardware for the network transmission of analog video. 

    Video Server Features

    1. Small size. Usually it has 1-4 analog video inputs, unlike a hard disk recorder that has more than a dozen video inputs, and it does not carry a hard disk randomly. Placing the storage device in the monitoring center is more conducive to the storage and protection of image data, which saves a lot of space.

    2. Simplicity. To transmit video data to the monitoring center through the currently rapidly developing, cost-effective computer communication network, only a cheap Category 5 network cable is needed. If the video server has a WIFI module inside and uses a wireless LAN, even the Category 5 network cable is saved.

    3. Powerful central control. An industrial standard server and a set of control management application software can run the entire monitoring system. Users only need to open the client program on a computer connected to the Internet and enter the IP address of the corresponding video server to conduct comprehensive remote monitoring. Any authorized client can directly access any camera and can also access the monitored images through the central server.

    4. Easy to upgrade and fully scalable. More cameras can be easily added, and the central server can be easily upgraded to faster processors, larger capacity disk drives, and greater bandwidth in the future.

    Video Server Highlights

    1. Operating system

    In fact, the development of an operating system is a very difficult technical issue. It is not an exaggeration to list it as a core technology. However, because of the difficulty, it is too expensive to develop an operating system for DM642 just for the development of a video server. Therefore, we recommend two options: (1) Purchase an operating system from a TI third party. There is already a TI third party that can provide a Linux operating system for DM642. However, the details are not yet clear.

    2. Use the BIOS provided by TI

    BIOS is a very small core that provides the most basic functions of the operating system. Users can develop applications on it. However, development and debugging are relatively difficult. Considering the development cost and the reliability of the operating system, we chose TI.

    3. Access control of network video server resources

    In order to meet the actual needs of monitoring, it is generally necessary to add serial ports, alarm I/O, hard disk and other resources to the video server. Because the network is not *, it is very important to control and access these resources in a unified manner *, timely and efficiently. We have specially developed the NRCAP protocol to solve these problems. For the details of the protocol, interested readers can contact us.

    4. NAT Issues

    Because the actual network conditions vary greatly and users have various needs, it is easy to encounter problems with the LAN and the Internet in the same system. At this time, how to solve the conversion between the internal and external addresses at the gateway must be considered. It is generally difficult to provide a unified solution suitable for various situations, so developers need to define several solutions for the most common network situations for users to choose from.

    5. Audio and video synchronization

    Due to the inherent characteristics of network transmission, it is impossible for sound data and video data to arrive at the client evenly from the network video server. If the client does not perform any correction processing, it is difficult to ensure the synchronous output of audio and video. Generally, timestamp information can be embedded in the data packet, and the client determines the appropriate playback time of the media data based on this information. At the same time, it should be emphasized that the video data is finally a frame-by-frame image, that is, it can be considered as an isolated point on the playback timeline, while the audio data is a segment of data, that is, it can be considered as continuous on the playback timeline, so the timing of the synchronous playback of the two media is different.

    6. Dynamic IP

    Since many users now use dial-up Internet access, the IP of the video server is dynamic. How the client can timely know the IP of the video server to be monitored is a problem that must be solved. We have defined a set of CDDNS protocols. After the video server is started, it will register its information with the CDDNS server regularly according to the CDDNS protocol. Users can obtain the IP of the video server by querying the CDDNS server.

    7. Moving target detection

    Many scenes in security monitoring are usually static. Once there is a moving target, the user hopes to be notified. When developing a detection algorithm, the selection of the detection threshold is a special issue that needs to be studied. It is necessary to consider many issues such as camera noise, on-site lighting, size and speed of the moving target, etc.

    8. File System

    Some video servers have local storage functions, which can effectively prevent the loss of important data when there is a network failure. Considering the versatility, it is recommended that developers choose a mainstream file system. When implementing on the DM642 platform, we implemented the FAT32 file system with only the support of TIBIOS. Practice has proved that it is stable and reliable, and users are also happy to accept it. If the developer can run the operating system successfully, the file system will be very simple and no longer need to be considered separately.

    9. Automatic dialing

    This is a problem related to dynamic IP. It is listed separately because the solution is completely unrelated to CDDNS. Developers need to develop their own dial-up protocols such as PPPoE.

    10. File storage format

    Generally, developers should develop two file storage formats: dedicated format and universal format.

    For users who emphasize confidentiality, a dedicated storage format should generally be provided. Developers can easily achieve confidentiality by not disclosing the file format. For users who emphasize ease of use, data should generally be stored as AVI files, and then user-installable plug-ins should be provided.