Application of the hottest MPEG4 video compression

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Application of MPEG4 video compression in the field of digital security


1. The latest developments in MPEG4 video compression/embedded technology

1.1 From the recent security exhibition, we can clearly feel that there are many manufacturers developing digital video surveillance products in China, and the competition is also very fierce. From the perspective of manufacturers involved, they can be roughly divided into three categories: machine suppliers, kit suppliers (board + software), and compression board suppliers, Among them, the whole machine suppliers account for the vast majority; From the perspective of DVR compression technology, it can also be roughly divided into three categories: MJPEG, MPEG1 and mpeg4. MJPEG technology is mainly used by products in South Korea and Taiwan, MPEG1 technology is mainly used by domestic manufacturers, and MPEG4 technology is generally accepted by the market in the way of hard compression and soft compression

embedded digital video system is the fastest growing part in the field of digital security at present, and it is the latest direction of the development of digital video technology. The adoption of embedded technology makes DVR break away from the traditional PC structure and windows operating system. The system has a fundamental improvement in stability, applicability and maintainability, which is an inevitable step for DVR to move from engineering products to consumer products. At present, the domestic embedded video system is mainly divided into the following parts: embedded hard disk video system, embedded video on the host, use a frame level bar to level the force value data in the two directions perpendicular to each other on the outer ring of the working oil cylinder (or column), and directly display the server and network camera. From the perspective of operating system, it is mainly composed of RTOS such as uClinux, VxWorks, PSOs, UCOS, etc

multimedia monitoring system is also a direction of continuous development in the field of video monitoring. Multimedia monitoring technology, which appeared in the 1990s, once blew a new wind in the field of video monitoring. With the emergence of DVR system, multimedia monitoring technology is also developing. At present, DVR systems generally lack the ability of TV wall display and matrix video switching. The perfect combination of digital matrix and DVR can not only ensure the strong matrix switching ability of the system, but also make full use of the strong video recording and network transmission ability of DVR, which is especially suitable for the application of large-scale video monitoring systems. 1.2. From the perspective of market application, at present, from the perspective of the application object of DVR, it is mainly divided into two categories, namely, environmental security monitoring and bank teller system monitoring. Especially through two years of market training, technical publicity and practical application, the advantages of digital hard disk video technology have been gradually recognized by the domestic banking system, and major banks in many provinces have gradually introduced hard disk video system into the teller system, From this point of view alone, DVR system has broad market application prospects, and will be more widely applied in Telecom, electric power, public security, customs, justice and other departments in the future

from the perspective of video compression, the technical requirements for DVR in the two applications are different. Security monitoring requires a large number of channels and does not require real-time video recording, while the bank teller system requires a small number of channels, but requires high definition and real-time video recording. Considering the current DVR products, the DVR of MJPEG compression standard is mainly used in the field of security, and the MPEG1 compression standard is mainly used in the field of bank teller system

peg, MPEG1 technical analysis and defects

no matter what compression technology is adopted, the end user is most concerned about several factors: clarity, storage capacity, stability and price. Using different compression technologies will greatly affect the above factors


mjpeg (motion JPEG) compression technology is mainly a technology developed based on static video compression. Its main feature is that it basically does not consider the changes between different frames in the video stream, and only compresses a frame separately. The current video card based on this technology also mainly completes the digital video capture function. In the background, the CPU or a special JPEG chip completes the compression stroke range dispersion, as shown in Figure 1

mjpeg compression technology can obtain video images with high definition, and can flexibly set the definition of each channel of video and the number of compressed frames, but the cost is that under the condition of ensuring high definition of each channel, real-time compression cannot be completed due to the limitation of processing speed, and there is a strong phenomenon of frame loss. At the same time, a large amount of redundant information is repeatedly stored due to the failure to consider the changes between frames, so the space occupied by a single frame of video is large, Currently, the most popular MJPEG technology can only achieve 3k/frame, usually 8~20k! Simple calculation shows that even if the frame is lost for video recording, it will also consume a lot of hard disk space, especially in the field of security monitoring. Because there are many surveillance cameras (16 channels are usually used), and high-definition video recording is carried out at the same time, it is very amazing to ensure the video storage capacity of one month, which is even far more than that of MPEG1 real-time video technology products. It is believed that users who have used this technology product are deeply impressed


mpeg1 real-time video compression technology is the mainstream of DVR products in the current market

mpeg-1 compression standard was formulated in 1992. It is designed for industrial standards and can be applied to devices with different bandwidths, such as CD-ROM, video CD, cd-i. It can compress the image with SIF standard resolution (352x240 for NTSC system; 352x288 for P data backup: the test data can be saved in any hard disk partition, Al System). The transmission rate is 1.5mbits/sec (minimum 192kbits/sec), plays 30 frames per second, has CD (refers to compact disc) sound quality, and the quality level is basically equivalent to VHS. The maximum encoding rate of MPEG1 can reach mbits/sec, but with the increase of the rate, the decoded image quality decreases

compared with MJPEG technology, MPEG1 has significantly improved in real-time compression, data volume per frame, and processing speed. For example, in the domestic PAL system, MPEG1 can meet the multi-channel compression speed of 25 frames per second (16 channels), and the size of each frame is only 2K under the 500kbit/sec compressed code stream (352*288). Simple calculation shows that the video recording capacity of MPEG1 products is tolerable (less than 8 channels) of the current hard disk capacity. At present, MPEG1 products of domestic DVR manufacturers basically use compression chips from Israeli or Taiwan companies through hardware compression technology

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