With the popularization of the Internet and the improvement of the network environment, network video surveillance has developed rapidly. The networked monitoring has become a trend in the security industry. For network video surveillance, the video server is an important component of the entire system and is an analog video. The network transmission provides the core hardware.
1, operating system
In fact, the development of the operating system is a very difficult technical problem. The list of core technologies is by no means excessive. However, because of the difficulty, it is too expensive to develop an operating system on the DM642 for the development of video servers. Therefore, we suggest that there are two options: (1) Purchase TI's third-party operating system. There are already TI third parties that can provide the Linux operating system on the DM642. However, the details are not yet clear.
2. Use TI's BIOS
The 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 cost of development and the availability 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, and hard disk resources to the video server. Because the network is inaccessible, how can these resources be unified in a timely, efficient manner? The control of access is a very important issue. We have specifically formulated the NRCAP agreement to solve these problems. With regard to the details of the agreement, interested readers can contact us.
4, NAT problem
Because the actual conditions of the network are very different, and the user's needs are various, it is easy to encounter the problems existing in the same system between the local area network and the Internet. In this case, how to resolve the conversion between the network address and the external network address in 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 conditions for the user to choose.
5, audio and video synchronization
Due to the inherent characteristics of network transmission, the arrival of voice data and video data from the network video server to the client cannot be uniform. If the client does not do any correction processing, it is difficult to ensure synchronized output of audio and video. Generally, time stamp information can be embedded in the data packet, and the client decides the appropriate playing time of the media data according to the information. At the same time, it is emphasized that the video data is a frame-by-frame image at the end, that is, it can be considered as an isolated point on the playback time axis, and the audio data is a period, a period of data, that is, on the playback time axis. Think it is continuous, so the two media are different in the timing of synchronous playback.
6, dynamic IP
Since many users are now dial-up, the IP of the video server is dynamic in this case. How the client knows in a timely manner that the IP of the video server to be monitored is a problem that must be solved. We have defined a CDDNS protocol. After the video server is started, it will register its own information with the CDDNS server according to the CDDNS protocol. Users can obtain the IP of the video server by querying the CDDNS server.
7, moving target detection
Many scenarios in security monitoring are usually stationary. Once there is a moving target, the user wants to be notified. In the development of detection algorithms, the selection of detection thresholds is a special issue to be studied. There are many issues to consider such as the noise of the camera, the lighting of the scene, the size and speed of the moving target.
8, the file system
Some video servers have local storage capabilities, which can effectively prevent the loss of important data in the event of a network failure. Taking into account the versatility, it is recommended that developers choose a mainstream file system. When implemented on the DM642 platform, with the support of only TIBIOS, we implemented the FAT32 file system, which proved to be stable and user friendly. If the development company can run a successful operating system, the file system is very simple and can be considered separately.
9, automatic dialing
This is a problem related to dynamic IP. It is listed separately because the problem is completely irrelevant to CDDNS. Developers need to develop their own dial-up protocols such as pppoe.
10, file storage format
General development vendors should develop two file storage formats: proprietary formats and common formats.
Users who emphasize confidentiality should generally provide a dedicated storage format. Developers can easily achieve confidentiality through a non-disclosure file format. Users who emphasize ease of use should generally store data as AVI files and then provide user-installable plug-ins.
1, operating system
In fact, the development of the operating system is a very difficult technical problem. The list of core technologies is by no means excessive. However, because of the difficulty, it is too expensive to develop an operating system on the DM642 for the development of video servers. Therefore, we suggest that there are two options: (1) Purchase TI's third-party operating system. There are already TI third parties that can provide the Linux operating system on the DM642. However, the details are not yet clear.
2. Use TI's BIOS
The 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 cost of development and the availability 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, and hard disk resources to the video server. Because the network is inaccessible, how can these resources be unified in a timely, efficient manner? The control of access is a very important issue. We have specifically formulated the NRCAP agreement to solve these problems. With regard to the details of the agreement, interested readers can contact us.
4, NAT problem
Because the actual conditions of the network are very different, and the user's needs are various, it is easy to encounter the problems existing in the same system between the local area network and the Internet. In this case, how to resolve the conversion between the network address and the external network address in 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 conditions for the user to choose.
5, audio and video synchronization
Due to the inherent characteristics of network transmission, the arrival of voice data and video data from the network video server to the client cannot be uniform. If the client does not do any correction processing, it is difficult to ensure synchronized output of audio and video. Generally, time stamp information can be embedded in the data packet, and the client decides the appropriate playing time of the media data according to the information. At the same time, it is emphasized that the video data is a frame-by-frame image at the end, that is, it can be considered as an isolated point on the playback time axis, and the audio data is a period, a period of data, that is, on the playback time axis. Think it is continuous, so the two media are different in the timing of synchronous playback.
6, dynamic IP
Since many users are now dial-up, the IP of the video server is dynamic in this case. How the client knows in a timely manner that the IP of the video server to be monitored is a problem that must be solved. We have defined a CDDNS protocol. After the video server is started, it will register its own information with the CDDNS server according to the CDDNS protocol. Users can obtain the IP of the video server by querying the CDDNS server.
7, moving target detection
Many scenarios in security monitoring are usually stationary. Once there is a moving target, the user wants to be notified. In the development of detection algorithms, the selection of detection thresholds is a special issue to be studied. There are many issues to consider such as the noise of the camera, the lighting of the scene, the size and speed of the moving target.
8, the file system
Some video servers have local storage capabilities, which can effectively prevent the loss of important data in the event of a network failure. Taking into account the versatility, it is recommended that developers choose a mainstream file system. When implemented on the DM642 platform, with the support of only TIBIOS, we implemented the FAT32 file system, which proved to be stable and user friendly. If the development company can run a successful operating system, the file system is very simple and can be considered separately.
9, automatic dialing
This is a problem related to dynamic IP. It is listed separately because the problem is completely irrelevant to CDDNS. Developers need to develop their own dial-up protocols such as pppoe.
10, file storage format
General development vendors should develop two file storage formats: proprietary formats and common formats.
Users who emphasize confidentiality should generally provide a dedicated storage format. Developers can easily achieve confidentiality through a non-disclosure file format. Users who emphasize ease of use should generally store data as AVI files and then provide user-installable plug-ins.
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