ARM7 Embedded Single-Chip Microcomputer Video Alarm System Based on GPRS

Using small embedded devices centered on single-chip application systems to collect data and effectively transmit data through the network has become a research focus in the field of data acquisition. Since embedded single-chip microcomputer systems integrate single-chip microcomputers and embedded systems, embedded single-chip microcomputer systems are widely used in application fields that require high real-time, high-speed and intelligence. At present, most computer image processing systems are CCD cameras + video cards + computers, and have complex structures, high costs, and large volumes. Due to the limitations of computer operating systems, image processing has poor real-time performance. In view of the defects of traditional image acquisition systems, this paper discusses the application of embedded systems based on ARM7S3C44BOX series 32-bit single-chip microcomputers in image acquisition.

1 Image processing of embedded imaging systems
1.1 ARM7 architecture
ARM processors are high-performance, low-power embedded microprocessors and are the most widely used series of devices in 32-bit and 64-bit embedded processors. The ARM7 processor is a member of the ARM processor family and is a widely used 32-bit high-performance embedded RISC processor. The ARM7 processor has a high-performance 32-bit ARM instruction set and a high-code density 16-bit THUMB instruction set. ARM7 consists of a processor core, a TAP controller for boundary scan, and an in-circuit emulator (ICEBreaker). The bidirectional data bus D[31:1] is split into unidirectional input and output buses for compatibility with various external memories. The processor components and their main signal paths are shown in Figure 1.

1.2 Composition and working principle of video alarm system
The video alarm system mainly includes four modules: image acquisition, image information processing, data communication, and alarm. Its composition structure is shown in Figure 2.
In Figure 2, the wireless camera is used to capture the live video image in real time, and the video information is sent to the alarm host through the wireless transmitter in accordance with the GPRS wireless transmission protocol, and the analog-to-digital conversion, video compression and video transmission of the video image are completed at the host. The wireless alarm sensor is used to receive the alarm information, and then send the identification code of the device to the alarm host through the wireless RF transmitter and in accordance with the GPRS wireless transmission protocol. The embedded alarm host ARM7S3C44BOX is the core component of the entire system. It obtains the alarm information or the live image of the alarm video in time through the wireless RF receiver, and completes the A/D conversion, encoding, compression and transmission of the image information, and then sends the alarm information or the live image to the wireless terminal of the legal user through the wireless network in accordance with the GPRS wireless transmission protocol. At the same time, it receives the request and configuration information of the wireless terminal. The wireless terminal can be a mobile phone, which can receive the alarm information through MMS, and can also be used to display the device to receive the alarm
video.
1.3 Technical Analysis of the System
The core technologies included in the digital video surveillance system are summarized into the following three aspects: digital video coding and compression technology, high-efficiency large-capacity storage technology and network technology.
1) Digital video coding and compression technology The current digital video coding and compression technologies mainly include: MPEG-1, MPEG-2, H263, MPEG-4, Wavelet, JPEG, etc. This system adopts the MPEG-4 video coding standard. The MPEG-4 video coding standard supports most of the functions in MPEG-1 and MPEG-2, and can provide rectangular images under different video standard source formats, bit rates, and frame rates, and supports lower spatial resolution (lower than 352x288 pixels) and lower frame rates (lower than 15 Hz). The encoding of the MPEG-4 standard is object-based, which is convenient for operating and controlling objects.
2) Storage technology Storage technology is a very important indicator of digital video surveillance systems. At present, the mainstream Windows uses the FAT32 file system, and the Windows file system has a high efficiency in managing files. This system improves and optimizes the original file system. Make it adapt to the storage of video files, improve the storage speed and multi-channel concurrency capabilities.
3) Network transmission technology Network video real-time transmission, based on the real-time transmission protocol, realizes the network transmission of audio and video data, and ensures the service of digital video network transmission. This system lays the foundation for the wide application of the entire system based on the actual needs and quality of network transmission.

2 Program flow and compression principle of software and hardware
2.1 Program flow
The system first completes the configuration of clock frequency and working mode, and then initializes the video processor I2C. When the system is working normally, it is in the driver polling state. When the network connection signal is detected, it responds to the command request, calls the image acquisition function or network transmission function, and returns to the driver polling waiting state after completing the image acquisition and network transmission. The software implementation of video data acquisition and network transmission is based on the software modules provided by the ARM7S3C2410X development board. Add IPModules' IPOS, IPStack, system program flow chart IPEthernet, I2C and other modules in the project configuration file, and read and write I2C and transform data into IP packets by calling dedicated library functions. The main I2C bus control functions used in this system design are: opening device file function v41_open(), initialization function, v41_picture(), initialization channels function v41_get_channels() and v41_switch_channel(), initialization audios function v41_get_audios, setting norm function v41_set_norm(), closing device file function v41_close(), initialization grap: 4l_grap_init(), setting palette function v41_set_palette(), function v41_grap_frame() that actually puts the image into the memory mapped by mmap(), and after imitating the acquisition function device_get_address() to obtain the frame image data, the frame image data is output into a PPM format file. The program flow of the system is shown in Figure 3. [page]

2.2 Compression principles of software and hardware
2.2.1 Software compression principles
For digital video processing, digital video information must be compressed before it can be transmitted and stored. For example, for a PAL color digital video with an image size of 352x288 (pixels) and 25 frames/s, if each pixel of each color is represented by 8 bits, the bit rate is as high as 58 Mbit/s. If 1 hour of such uncompressed video is stored, 26 GB of disk space will be occupied. If the appropriate compression method and encoder parameters are used, the same video can still have good quality, and the bit rate is only about 200 kbit/s. After compression, the transmission bandwidth and storage space are greatly saved.
Each image of the active video has spatial redundancy and psychological visual redundancy. The appropriate intra-frame compression algorithm can be used to remove the intra-frame redundancy. For active videos, there is also similarity between adjacent images, which produces inter-frame redundancy. The motion compensation encoding method can be used to remove the inter-frame redundancy. Combining the above two compression algorithms, the compression of digital video can be achieved. In the field of digital video surveillance, the compression of video signals is generally carried out by using the compression encoding method recommended by MPEG-4. The specific compression algorithm is shown in Figure 4.

2.2.2 Principle of hardware compression
Based on PC software implementation, the compression coding scheme is based on MPEG or MJPEG. Under a reasonable PC work surface, software compression can only process one video signal in real time. Using hardware for video coding compression, a computer has up to 4 video compression encoders implemented by hardware, thus becoming a video server. The function of a video server using hardware compression scheme is equivalent to that of several high-performance computers using software compression scheme, with greatly reduced cost, stronger functions and higher stability. There are many hardware compression devices that can be used. Using the video compression coding scheme of DSP digital signal processor, multiple algorithms can be flexibly implemented through code programming to achieve compression and decompression of images, voices and sounds. The principle of hardware compression is shown in Figure 5.

3 Conclusion
The ARM7 embedded single-chip video alarm system based on GPRS is a new type of alarm system that combines traditional alarm systems and video surveillance systems by utilizing the development results of wireless communication technology. It has the characteristics of flexible configuration and installation. High reliability and good real-time performance. The system design strives to be practical. In addition to automatic monitoring and alarm, it also has an external video recorder or video acquisition card to record the scene of the crime scene; the hardware adopts a distributed structure and can be cascaded in multiple levels, which is easy to expand according to actual requirements; the system itself uses components with low energy consumption and can work continuously for a long time; the monitoring range is large and can be used for indoor or outdoor monitoring; the peripherals required by the system, such as televisions, cameras, and video recorders, are all common household appliances, which are easy to operate, reliable in performance, and low in price. The system can effectively detect alarms for most low- and medium-speed moving objects. It has been applied to specific system implementations and has a good effect. The future development direction of this system is undoubtedly an intelligent monitoring and management system that integrates network technology, multimedia technology, and monitoring technology. With the maturity of technology and better cost performance, it will surely have broad application prospects.