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ARM9-based video surveillance terminal design and implementation

In Electronic Infomation Category: A | on April 18,2011

Abstract: The design of a S3C2410-based embedded operating system, hardware platform and TPS61028DRCR datasheet and remote video monitoring system terminal, introduced the embedded system hardware and TPS61028DRCR price and software design and TPS61028DRCR suppliers and architecture of the system video capture, MPEG4 compression, network transmission analyzed in detail. Video surveillance system with the traditional comparison, the program has small size, low cost, good stability.

Security video surveillance system is an important component of the system, it has an intuitive, convenient, abundant information has been widely used in many occasions. Traditional digital video surveillance platform for the general + PC-based video capture card in the form of a system size of the program, high cost, stability is not good enough and other shortcomings. As embedded system monitoring, and video compression technology matures, and the popularity of the high network bandwidth, through an embedded platform for video signal acquisition, compression, network transmission, video surveillance has become possible. The design uses a Korea-based Samsung ARM920T embedded processor core, and the internationally popular MPEG4 compression technology and streaming media transmission technology, the development of high reliability, low cost, small size, low power consumption, remote video monitoring system terminal.

1 System hardware platform

Hardware platform shown in Figure 1. The design is used in Samsungs S3C2410 ARM embedded processors, clocked at up to 203 MHz. Built a wealth of peripheral resources, including memory, serial, USB, Ethernet port, and control equipment, primarily for hand-held equipment and cost-effective, low-power applications. S3C2410 as the system control unit, and its superior performance, rich piece internal and external resources, the optimization of video processing capabilities, low power consumption become the system of choice. The core board built 64 MK9F1208 of NAND Flash, 2MSST39VF1601 the Nor Flash, and Ethernet control chip States Samsung S3C2410 ARM embedded processors, clocked at up to 203 MHz. Built a wealth of peripheral resources, including memory, serial port, Ethernet port and USB interface control such as equipment, mainly for handheld devices, and cost-effective, low-power applications. S3C2410 as the system control unit, and its superior performance, rich piece internal and external resources, the optimization of video processing capabilities, low power consumption become the system of choice. The core board built 64 MK9F1208 of NAND Flash, 2MSST39VF1601 the Nor Flash, and Ethernet control chip CS8900Q3. Two UART serial port supports RS232 protocol for communication and control, and PC camera, baud rate up to 115 200 bps. external USB camera used is based on Vimicro Z301 chip speed camera. Pixel 130 million, the median 24-bit color, the largest up to 30 frames, the picture smooth, clear, support: S3C2410, QQ2440v3 mini2440 other ARM9 development board, plug and play, embedded systems development is a good choice.

Figure 1 System hardware platform

The system through the USB camera, video capture raw data, S3C2410 as the core of the central control and data processing center, the main terminal to complete control of video capture and video compression, and compressed video data package to form a standard network data flow transferred to the Internet.

2 software design

System software design includes the following aspects: cross compiler build environment, USB video capture, video encoding and video streaming network. System software architecture shown in Figure 2.

Figure 2 System software architecture

2. 1 cross-compiler environment to build

The limited resources of embedded development board, development board is not directly in the development and debugging, cross compiler debugging needs to develop and debug the way, given the strong network of embedded Linux support, source code is completely open, portability, network powerful features, use it as a system software platform. Development of the system to be installed before the Linux operating system, then the host PC, the establishment of the cross-compiler environment. Install the corresponding development board ARM cross compiler cross-3. 3. 2. Tar. Bz2. Thus, an embedded ARM-LINU X cross-compiler environment to the next successful build.

2. 2 video acquisition system

Video capture through an embedded Linux operating system calls V4L (video4linux) and video driver to complete.

V ideo4linux is linux and embedded video streaming system based imaging systems. It is the linux kernel support for imaging equipment in a group of API (application program interfaces), if appropriate video capture card with the driver, video4linux image acquisition can be achieved, AM / FM radio, video CODEC, channel switching and other functions. At present, V4L mainly used in video streaming video systems and embedded systems, such as: distance learning, telemedicine, video conferencing, video surveillance, video telephony and so on. It is divided into 2 layers-style architecture, the upper video4linux driver itself, the lower the driver for the imaging equipment, such as the design of the Z301 camera Vimicro chipset drivers. In the Linux operating system, the external device as a device file management, therefore, the operation of external devices paired device file to change the operation. Acquisition program calls V4L API for reading on the device file, you can capture video data.

The development board comes with Linux kernel does not support Vimicro camera, so to download Z301 driver chips in the patch, corresponding to the ARM-Linux version. Use of patch command to fight in the kernel. When compiling the kernel, will usb-> support there SPCCA5XX options as modules loaded, the boot sequence when the load Video4linux and Spca5x x module loaded successful, will see the device files / dev / video0 paper on the USB camera driver loaded successfully, the terminal can be set for operating the video camera collected.

2. 3 video coding

Video surveillance system requirements is to achieve real-time, as collected through the camera directly to the large amount of original image data, and network bandwidth is limited, so be sure to go through before video encoding compression processing for network transmission, video compression is the core of the design.

Currently, many video coding algorithms, the most influential and widely applied international standards H26X series and MPEG series. MPEG family is MPEG-4 ISO / IEC as the official standard number ISO / IEC14496, it is not only a certain bit rate for video, audio coding, multimedia systems pay more attention to the interaction and flexibility. This standard is mainly used in video telephony, video mail and so on, requiring a lower transmission rate, in the 4 800 ~ * 00 bit / s between, it can use a very narrow bandwidth, the frame reconstruction, data compression, with the least the data best image quality. Compared with MPEG1 and MPEG2, MPEG4 feature is more suitable for interactive AV services, and remote monitoring. MPEG-4 is the first from passive to active so that you (not just viewing, allowing you to join, that is, interactive) dynamic image standards.

Present, based on MPEG-4 video codec standard more commonly used with Microsofts development msmpegv3, and the open source xvid and ffmpeg. Ffmpeg is a complete recording, conversion, streaming audio and video solution, it is a very good compatibility, including the industry-leading audio and video codec library for the embedded video monitoring system is a very good choice. System uses FFMPEG for video encoding, compression. Encoding process and the main use FFMPEGs libavcodec libavformat two libraries, many video file formats generally define how the video stream is encoded into a separate file, not clear that the use of coding tools, libavformat librarys main function is to The syntax of video file formats, sort out and carve it from the original video stream flow, libavcodec library functions are handled in accordance with the original stream format video stream encoding. Video encoding process is as follows, first open the file if (av_open_input_file (& pFormatCtx, f ilename, NU LL, 0, NU LL)! = 0).

Stream file and then read the information select the appropriate codec, and open the corresponding encoder, the encoder need to use the libavformat library to read the data packets, filter out unwanted non-video stream data, and then libavcodec library function call loop GetNestFrame. to deal with every frame of data encoded. By testing a 40s video of the original document, a resolution of 800 600, frame rate is 30, size 246 M, compressed to FLV format, frame rate is 25, a resolution of 320 240, bit rate is 500 K / s, the compressed size of less than 2M, compression ratio of 120: 1. get the video file is very clear, smooth, resolution, frame rate, time rate, can change the video format, very easy to achieve real-time video surveillance requirements.

2. 4 video data stream network transmission

Use of camera equipment, video images collected by the ffmpeg MPEG-4 compressed video stream for the future, subject to network transmission. Real-time video surveillance systems require low latency and small packet loss rate, due to TCP retransmission mechanism brings greater delay, UDP itself Qos not provide any guarantees, requiring real-time transport protocol ( RTP) and real-time control protocol (RTCP) for use to provide real-time data transmission and Internet Qos services to meet the requirements of real-time transmission of video data. RTP data protocol is responsible for packaging and streaming media data stream real-time transmission to complete in itself and can not transmit data packets in sequence to provide a reliable guarantee, does not provide flow control and congestion control. Reliability of transmission is used in conjunction with its real-time transport control protocol RTCP to be responsible for completion. RTP is the real-time streaming media transmission problem solve the best way to block the video transmission system using RTP and RT CP protocol.

RTP transport layer protocol, RFC in the definition of the RTP process is not tailored to its underlying protocol. RT P does not provide network connectivity, typically in use and other agreements with the U DP match. U DP RTP protocol uses the client * and RT P U DP implementation procedures written in the upper, it can be seen as the transport layer of the upper sub-layer. RTP packet encapsulates the encoded video data, each RTP packet is encapsulated in UDP paragraph of information, and then encapsulated in IP packets to prepare for network transmission. Figure 3 shows the RTP / RTCP protocol stack in the position.

Figure 3 RT P / RPTCP position in the protocol stack

In the actual development process, RTP execution was seen as part of the application, which is integrated into the application. In the transmitter, first create the RT P session, the RTP packet to create an application program written to perform RTP protocol, then the application will be sent to the UDP RTP packets the socket interface. Similarly, at the receiving end, RTP packets through UDP socket interface input to the application and implementation procedures for RT P Agreement is written to be withdrawn from the RTP media packet data applications.

3 Conclusion

Paper architecture is designed based on S3C2410 ARM9 embedded video surveillance system. Completed a video image capture, encoding, transmission and other functions. It not only has strong anti-interference ability, suitable for long-distance transmission, can encryption, full use of existing network resources and many other advantages, and portability, low power, low cost, easy to install, easy to use and easy maintenance, etc., and using software to achieve its main function is conducive to development and upgrade the secondary system, its application scope and prospects are very bright.

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