With the rapid development of computer and network technology, especially the increasingly mature video codec technology, the rapid improvement of computer processing power, and the gradual popularization of broadband, real-time application of Internet-based video networks has been widely adopted in many industries and government departments. Especially in the banking, broadcasting, oil, electric power and other industries, there have been many successful cases.
When it comes to Internet-based video network real-time applications, we may think more about video telephony and video conferencing systems, TV network live broadcasts, distance education, and so on. These Internet video real-time applications require high performance requirements for both hardware and software. They require high frame rates and low bit rates, so they require powerful processing power (including algorithms and chip processing capabilities). To have this processing power, expensive specialized equipment is often required.
For network digital video surveillance system security involved, due to the industry characteristics of the decision, more data collection points, you need to configure a large number of encoding devices, so compared to other real-time video network applications, 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 can not provide users with a complete solution.
For example, a bank's ATM centralized digital monitoring system may need to provide an Internet-based solution: broadband-based, narrow-band supplemented.
First, the original ATM machine the reserved private network transport service data entry needs, taking into account the requirements of business services and 24-hour video surveillance of the online 24-hour ATM machine, it is difficult to provide a solution, in the same private network, both to ensure The business data transmission is stable, and the monitoring picture is smooth. Therefore, we need to consider renting the line from the broadband operator and transmitting the video data through the broadband. Moreover, considering the operation mode and cost, many ATM machines 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 periodically inspects each monitoring point. Need to be online. In this case, it is not necessary to rent the line for the ATM machine all the year round, and only need to open ADSL, ISDN, or even connect by telephone line.
The past two years, domestic manufacturers continue to push high-performance, cost-effective video and audio compression cards and network monitoring equipment, making it possible, as described above ATM machines digital centralized monitoring system digital video network monitoring system based on Internet.
two. Overview of requirementsBut as a complete solution, we have to consider the question of how to handle dynamic IP addresses.
Whether it is ordinary telephone line dialing, or ISDN, ADSL, as long as the dynamic IP access method is adopted, this problem will be encountered. The so-called dynamic IP access mode means that users dynamically obtain IP addresses through virtual dial-up technology to conduct online services. Each 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 the IP address. However, because this IP address is dynamic, that is, once disconnected, the next time the Internet is connected, the ISP will assign a different public IP address.
If only one side of the encoding end (such as ATM) or the decoding end (such as the monitoring center) adopts dynamic IP access, the problem is easier to solve. In point-to-point communication, as long as one party can know the IP address in advance, it is possible to establish a handshake between the two parties, acquire the IP address of the other party, and communicate. But if both parties adopt dynamic IP access, 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 implementation and comparisonBelow we will introduce two solutions.
1> Apply for a dynamic domain name
There are many professional companies that offer dynamic domain name services on the Internet. The so-called dynamic domain name is to associate a fixed Internet domain name with a dynamic address IP in real time. In this way, no matter when the line is online, what is the assigned IP address, other users can always access the corresponding computer through the Internet domain name.
Dynamic domain name structure
As shown in Figure 1, as long as you choose a dynamic domain name service provider, you can get a fixed Internet domain name for free by registering on the company's website (each computer that uses the dynamic domain name service needs a separate domain name). Download and install the appropriate software provided by the company to complete the software configuration. In the future, as long as the computer is online, the dynamic domain name will automatically take effect.
The original digital video network monitoring system based on fixed IP addresses can almost directly use this mode. Of course, if the IP address of the remote monitoring point is pre-configured, it needs to be changed to the Internet domain name of the pre-configured remote monitoring point. When writing a program, you only need to call the corresponding API function to get the IP address corresponding to the Internet domain name.
The way to apply for a dynamic domain name has the following advantages: 1. Software development is simple, almost no need to modify the code; 2. Performance is relatively stable, the dynamic domain name service provided by a professional company is online 24 hours, 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, the cost is relatively low, and only need to pay the corresponding service fee for each computer that uses the dynamic domain name.
However, this method also has some shortcomings: 1. If the system is large, for example, there are 100 monitoring points, then each computer needs to pay N yuan for service fees every year, and the service fee of the monitoring system needs 100*N yuan. The cost is relatively high; 2. If the dynamic domain name resolution server requires some personalization features, it cannot be customized.
2> Custom IP Address Resolution Server
IP address resolution server mode structure
The customization mentioned here includes two ways, one is to develop the IP address resolution server software by itself, and the other is to purchase the corresponding software module.
As shown in Figure 2, no matter which method is used, it basically runs in the following mode: 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 retrieval information. When any two users access each other, they are accessed by means of an alias. Before the access, 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 make up for the lack of dynamic domain name mode, especially for large systems, you can save money and flexible customization. In order to solve the dynamic IP problem, you only need to pay extra to build an IP address resolution server, including the server's 24-hour online Internet access fee and the cost of applying for a fixed IP (of course, this server can also use dynamic domain name). Moreover, while customizing the IP address resolution server, other value-added services, such as authentication, billing, group management, etc., can be performed, similar to a GK.
Of course, compared with the dynamic domain name method, the biggest shortcoming of this method 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 operability.
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