one. market background
With the rapid development of computer and network technologies, especially the growing maturity of video codec technology, the rapid improvement of computer processing capabilities, and the increasing popularity of broadband, the real-time application of Internet-based video networks has been widely adopted in many industries and government departments. In particular, there have been many successful cases in industries such as banking, radio and television, petroleum, and electricity.
Referring to the real-time application of video networks based on the Internet, we may think more about video telephony and video conferencing systems, live broadcast of television networks, and distance education. These Internet video real-time applications have high performance requirements for hardware and software, and require both a high frame rate and a low code rate, and therefore require a sufficiently powerful processing capability (including algorithms and chip processing capabilities). To have such processing power, expensive specialized equipment is often required.
For the digital video network monitoring system involved in security, due to the characteristics of the industry, there are many data collection points and a large number of encoding devices need to be configured accordingly. Therefore, compared with other video network real-time applications, the price becomes a relatively sensitive factor. .
In the past, digital video network monitoring systems were basically based on local area networks or private networks. However, the actual application environment is difficult to guarantee such network conditions, so system integrators cannot provide users with a complete solution.
For example, the bank's ATM centralized digital monitoring system may need to provide Internet-based solutions: mainly broadband, supplemented by narrowband.
First, the original reserved private network entrance of the ATM machine needs to transmit service data. Taking into account the 24-hour online business service and 24-hour video monitoring requirements of the ATM machine, it is difficult to provide a solution. It is guaranteed on the same private network. The business data transmission is stable and the monitoring picture is smooth. Therefore, we need to consider leasing lines from broadband operators and transmitting video data over broadband. Moreover, from the operating mode and cost considerations, many ATMs do not need to transmit video data at any time, and often require the monitoring center to switch monitoring points only when an abnormality occurs, or when the monitoring center regularly inspects each monitoring point. Need online. In this case, you don't need to lease the line for the ATM machine all the year round. You only need to open ADSL, ISDN, and even connect through a telephone line.
In the past two years, domestic manufacturers have continuously introduced high-performance and cost-effective video and audio compression cards and network monitoring equipment, making it possible to use digital video network monitoring systems based on the Internet, such as the above-mentioned ATM digital centralized monitoring system.
two. Requirements Overview
But as a complete solution, we have to consider such a question: how to deal with dynamic IP addresses.
Whether it is the dialing of ordinary telephone lines, or ISDN, ADSL, as long as the use of dynamic IP access, will encounter this problem. The so-called dynamic IP access mode refers to the user through the virtual dial-up technology to obtain an IP address dynamically to launch Internet services. Every time a user connects to the Internet through an ordinary MODEM or through ISDN or ADSL dial-up, the ISP usually assigns a public IP address to the user. At this time, other users on the Internet can access the computer through this IP address. However, because this IP address is dynamic, that is, once disconnected, the ISP will assign another different public IP address the next time it connects to the Internet.
If only one side of the encoding end (such as the ATM machine) or the decoding end (such as the monitoring center) adopts the dynamic IP access method, the problem is easily solved. In point-to-point communication, as long as one party can know the IP address in advance, a handshake can be established between the two parties, and the IP address of the other party can be acquired for communication. However, if both parties adopt dynamic IP access methods, it will be troublesome. After a user dials a connection, he does not know the IP address of the monitoring center and cannot notify the other party's own IP address. Subsequent operations cannot be performed at all.
three. Solution realization and comparison
Below we will introduce two solutions.
1> Apply for a dynamic domain name.
There are many professional companies that provide dynamic domain name services on the Internet. The so-called dynamic domain name is a real-time mapping of a fixed Internet domain name and dynamic address IP. In this way, no matter what time the user goes online, the assigned IP address is the same. Other users can always access the corresponding computer through the Internet domain name.
Dynamic domain name structure chart
As shown in Figure 1, simply select a dynamic domain name service provider and register once on the company's website to get a free Internet domain name (each computer using the dynamic domain name service requires a separate domain name). Download and install the corresponding software provided by the company to complete the software configuration. In the future, as long as the computer is online, dynamic domain names will automatically take effect.
The original digital video network monitoring system based on a fixed IP address can almost directly use this mode. Of course, if the IP address of the remote monitoring point is configured in advance, it needs to be changed to the Internet domain name pre-configured with the remote monitoring point. When writing a program, you only need to call the corresponding API function to obtain the IP address corresponding to the Internet domain name.
The method of applying for a dynamic domain name has the following advantages: 1. The software development is simple, almost no need to modify the code; 2. The performance is relatively stable, the professional company provides dynamic domain name service 24 hours online, whether it is the stability of the IP address resolution module software or the server The stability is relatively high; 3. If the system is small, then the cost is relatively low, only need to pay the corresponding service fee to each computer that uses the dynamic domain name.
However, this method also has some deficiencies: 1. If the system is large in size, for example, there are 100 monitoring points, then each computer needs to pay service fee N yuan each year, and the service fee for the monitoring system needs 100*N yuan. The cost is relatively high; 2. If the dynamic domain name resolution server needs some personalized features, it cannot be customized.
2> Custom IP address resolution server.
IP address resolution server mode structure
The customization here refers to two ways. One is to develop the IP address resolution server software by itself and the second is to purchase the corresponding software module.
As shown in Figure 2, no matter which method is used, it is roughly run in the following modes: The monitoring center and all monitoring points are pre-defined with an alias. When each computer is online, its own IP address and corresponding alias are automatically sent to IP address resolution server. The IP address resolution server saves all IP addresses and corresponding aliases and generates search information. When any two users visit each other, they are accessed by using an alias. Before accessing the software, the software automatically connects with the IP address resolution server to obtain the corresponding IP address.
If you use a custom IP address resolution server solution, you can just make up for the lack of dynamic domain name methods, especially for large systems, you can save costs, flexible customization capabilities. In order to solve the dynamic IP problem, only need to pay an additional fee to build an IP address resolution server, including the server's 24-hour online access fee and the cost of applying for a fixed IP (of course, this server can also use the dynamic domain name). Moreover, other IP services such as authentication, accounting, and group management can be performed while customizing the IP address resolution server, similar to a GK.
Of course, compared with the dynamic domain name approach, the biggest drawback of this approach is that the workload of software development is relatively large.
There are other ways to solve the dynamic IP problem, but the above two solutions are relatively mature and more maneuverable.
Hangzhou Hikvision Digital Technology Co., Ltd. is a video and audio compression board and network hard disk video recorder professional manufacturer, Hangzhou Hikvision Digital Technology Co., Ltd. DS-800XM series network hard disk video recorder supports dynamic IP address, can Constitutes a large-scale monitoring system based on dynamic IP addresses. DS-800XM series network hard disk video recorder adopts MPEG-4 compression technology, supports RTP/RTCP flow control protocol, can dynamically track bandwidth changes, adjust the frame rate and image quality of compressed code stream, and is especially suitable for public networks such as INTERNET. On the application.
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