This application note describes the different compression techniques used by the current video surveillance system and some of the video compression standards, discusses the basic principles that use traditional CCTV and IP camera input to implement digital recording, ie, using H.264 video compression standards to be effective Data storage capacity, even if the low bit rate transmission rate is used, a higher network transmission image quality can be obtained.
Introduction The Simulation CCTV Security Monitoring System is transitioning to digital technology, and the demand for recording is an important factor in leading this trend. In a security monitoring system that requires video surveillance and recording, the analog VCR has been replaced by a digital video recorder (DVR). In safe monitoring applications, the DVR has an overfolded advantage with respect to the simulation VCR. Continuous video images are recorded, processed, processed, and transmitted over digital networks, almost any level of image quality requirements including HD (HD). Users can use digital processing technology, such as real-time analysis, on-site search, mobile, and activity detection alarms, remote access via IP networks. The storage cost of the physical carrier, such as a hard disk (HDD), a digital universal disc (DVD) or network storage (NAS), is only a part of the cost of analog tape costs. The use of digital recording and archiving technology also helps to permanently save video recording, which will lose image quality over time. All of these factors drive a standard of DVR as a video record in the field of security monitoring.
DVR Type Safety Monitoring Market has experienced several different DVR development phases. Embedded, mixed, and PC-based DVRs require basic video and audio collection units: mold / digital conversion, compression, playback, and network flow processing. Embedded DVR is a stand-alone device that accepts an analog CCTV camera input, compression and storage in local HDD; mixed DVR can accept analog CCTV and IP camera input, which use it as a video source; PC-based DVR follows the hardware compressed card Or Software Compact Programs running in the PC is integrated in the security monitoring station. The key features of different modules include: the number of video input channels, supported compression standards, recording quality, stream processing, and playback mode, storage capacity, and system capable of performing both functions simultaneously. Safety monitoring of the functional block diagram of the DVR system. For Maxim recommended security monitor DVR design, please visit: china.maxim-ic.com/dvr.
Video compression technology H.264 is a new industry standard for security monitoring DVR video compression. Compared to the previous generation MPEG-4, even MJPEG standard video technology, the advantage of H.264 is to have a higher compression ratio, which can provide high quality images for the security monitoring system. The H.264 higher compression ratio (two times that can reach the previous generation compression technology) can extend the capacity by 100%, and the generated file size is smaller, so that a longer period of time can be recorded on a fixed capacity storage device. In addition, H.264 compression techniques can transmit high quality images through the network with a very low code rate. If there is no efficient compression, a multi-camera security monitoring system will soon exceed the available bandwidth of the network. In order to extend the recording time, reduce the video code rate, the DVR system without H.264 compression technology has to reduce the recording frame rate or sharpness, thereby reducing image quality. In order to ensure the backward compatibility of the product, many systems still use traditional codec formats (MPEG-4 and MJPEG), but from the current development trend, H.264 has become the preferred codec technology of industry DVR. Maxim's H.264 series processor can support MJPEG video and playback, keep backward compatibility with the previous generation device.
DVR System Requirements Video Security Monitoring System is getting higher and higher for recording and displaying clear images. Early DVR video clarity is used in CIF (NTSC 360 x 240), and digital video quality is comparable to the simulated VCR it replaces. The low CIF is also suitable for the first generation of codec technology (MJPEG / MPEG-4), but the image compression of this technology is unable to compete for the requirements of HD systems. The current market demand and development trend are video recording (D1 NTSC 720 x 480) or "DVD quality". Compared with CIF, the processing capacity of each channel of the SD system has increased by 4 times. The H.264 codec technology representing the latest technology level is widely used in D1 definition or higher definition systems to ensure high efficiency compression ratio. Maxim's H.264 Series processor can flexibly set video definition to meet video quality requirements of different video systems. Another development trend in the field of video security and monitoring is full frame rate recording and storage. The full frame rate of the analog CCTV camera is 30 frames / sec (FPS) in the NTSC system, and the PAL is 25fps. Real-time video recording systems have increased by 2 to 4 times the processing capability requirements of each channel of real-time video recording systems, for example, 7.5FPS (25% of NTSC systems) or 15FPs (50% of NTSC system). In order to meet the processing needs of the new DVR design, there is a need for a powerful upgradeable system architecture. Over time, most of the video security monitoring systems in the current market use a mixed architecture of simulating CCTV equipment and digital network technology. The traditional digital device is based on early codec technology (MJPEG / MPEG-4), which requires new devices to support two format conversions. For example, the video signal collected by the IP camera of the current MJPEG compression algorithm must be re-encode the H.264 format in the DVR to achieve efficient storage and make full use of network bandwidth. The current DVR design must be able to accept multi-format digital video input (MJPEG / MPEG-4 / H.264) to protect early equipment investment. Maxim's H.264 series processor can perform MJPEG and MPEG2 decoding before re-encoding the H.264 format, supports new system video and data stream processing. , Reading the full text, the technology area
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