Abstract: At present, remote video surveillance systems have become an important part of smart homes. The intelligent monitoring system is based on the Android operating system platform, using a tablet computer as a client, downloading monitoring pictures from an IP camera through the HTTP protocol, and using a variety of algorithms to intelligently monitor each room or different angles in the home.
In recent years, video surveillance systems have been widely used in manufacturing companies, property management, unattended terminals, banks, transportation, warehouses and other fields. When there are objects and areas that need special attention in the family, the owner of the family can install a camera in the home environment where they are located, and observe the status remotely through the network, and can also monitor the progress of the situation through the network when an unexpected situation occurs. With the widespread popularity of smart mobile terminals, due to their unique portability and easy access to the network, mobile terminals have become an ideal choice for dynamic monitoring and on-site monitoring.
The client device of the video monitoring system designed in this paper is an Android tablet. The client obtains real-time monitoring pictures from IP cameras, uses different algorithms to determine whether people are in or out of the home according to different scenarios, marks the objects of interest and tracks them intelligently, and identifies each room The lighting situation and the use of household appliances such as TVs and computers can realize 4-channel intelligent monitoring at the same time.
1 Introduction of monitoring platform
1.1 Introduction to the client platform
The client uses the Android smart operating system. Android is the name of the open source mobile operating system based on the Linux platform released by Google on November 5, 2007. The platform is composed of an operating system, middleware, user interface and application software. The underlying Linux kernel only provides basic functions. Other application software is developed by the companies themselves, and some programs are written in Java.
Data from early 2011 shows that the Android operating system, which has only been officially listed for 2 years, has surpassed the Symbian system that has dominated 10 years and has become the most popular smartphone platform in the world. Now, the Android system is not only used in smart phones, but also rapidly expanded in the tablet market. At the same time, the Android smartphone operating system has five major advantages: openness, getting rid of the constraints of operators, rich application choices, and Google applications that developers do not have any restrictions and seamless integration.
1.2 Introduction to IP Camera
An IP camera is a device that can generate digital video streams and transmit the video streams through a wired or wireless network. It does not require additional software and hardware to transmit live digital images directly to the Internet, making it a worldwide All computers can view digital images of real-time activities through a browser. The IP camera supports TCP / IP, SMTP E-mail, HTTP and other Internet protocols, and supports various operating systems such as Windows, Unix, Mac and OS / 2.
The design uses Hikvision's DS-2DM1-502 network medium-speed smart dome camera, which supports the client to download monitoring pictures and H.264 code stream through HTTP protocol.
2 Programming principle and realization
2.1 Client design principles
The design uses the tablet PC of the Android system as the client, and the software flow of the client is shown in Figure 1.
The specific implementation of the system is roughly divided into two parts: connecting with an IP camera to obtain the required video stream; making corresponding judgment and response according to the monitoring scene.
2.1.1 Obtaining surveillance video
The client is connected to the IP camera via WiFi. After logging in the IP camera, the monitoring channel can be selected to realize 4-channel intelligent monitoring at the same time, that is, the basic situation of the home can be observed: whether there are people in and out of the home, whether someone is at home, and the objects that appear in the monitoring Carry out attention tracking to identify the lighting of each room and the use of household appliances such as TVs and computers. The client implementation method is to enable multi-threaded control of 4-channel monitoring tasks, so that each channel of monitoring tasks is relatively independent in order to change channels.
There are two specific implementation methods for multithreading, namely inheriting the Thread thread class and implementing the Runnable interface. If the client adopts the method of inheriting the Thread thread class, it cannot inherit other classes than the thread class, and the interface sub-thread must inherit the View view class, so this design uses the second method. In the monitoring implementation, each screen is a separate thread and a complete view. It is a class object that implements the Runnable interface and inherits the View class. Therefore, each object is independent of each other, and each monitoring screen is independent of each other, and the monitoring channel can be flexibly selected for background control management.
On the interface implementation, the main interface is a 4-channel monitoring window. After the initial selection of the monitoring channel, the monitoring picture sequence can be obtained through the HTTP protocol, algorithm processing is performed according to the scene, and the intelligent monitoring screen is played.
2.1.2 Program optimization
The client needs to call different intelligent monitoring algorithms according to different scenarios to judge and recognize the events that occur. This process includes a large number of image processing operations, such as graying, background modeling differences, median filtering, and morphological operations. . The development language of the Android operating system is Java, but the running speed of pure Java programming image processing programs on Android phones is a big problem. Calling the C program module in the Java program through the JNI (Java NaTIve Interface) technology obviously improves the running speed of the application program. The author intercepted 40 frames as the observation object. The average running time of the main operation steps of the program is shown in Table 1, from which we can see that the running time has been shortened to 1/18 ~ 1/17.
Table 1 Comparison of running time between main algorithms Java and JNI
2.2 Function and implementation
The intelligent monitoring system of this design has three major functions: manage all the cameras in the house, flexibly select the monitoring point; execute a variety of different intelligent algorithms; and be able to link with other networked devices to achieve smart home control.
The author tested the system with different actual scenarios. The functional description and experimental results of the system are as follows.
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