模拟CCTV安全监控系统正在向数字技术过渡，对于录像的需求是引领这一趋势的重要因素。在需要视频监控和录像的安全监控系统中，模拟VCR已经被数字录像机(DVR)取代。安全监控应用中，相对于模拟VCR，DVR具有压倒性的优势。连续的视频图像按照数字形式记录、处理，并通过数字网络传输，几乎可以满足包括高清(HD)在内的任何等级的图像质量需求。用户可以采用数字处理技术，例如实时分析、现场搜索、移动和活动检测报警，通过IP网络进行远程访问。物理载体的存储成本，例如硬盘(HDD)、数字通用光盘(DVD)或网络存储(NAS)器，仅仅是模拟录像带成本的几分之一。利用数字录像和存档技术还有助于永久保存视频录像，不会随着时间的推移而损失影像质量。所有这些因素都驱使安全监控领域将DVR作为视频记录的标准。
Analog CCTV security monitoring system is transitioning to digital technology, and the demand for video is an important factor leading this trend. Analog VCR has been replaced by digital video recorders (DVR) in security monitoring systems that require video monitoring and video recording. DVR has an overwhelming advantage over analog VCR in security monitoring applications. Continuous video images are recorded and processed in digital form and transmitted over the digital network to meet almost any level of image quality requirements including HD. Users can adopt digital processing technologies, such as real-time analysis, on-site search, mobile and activity detection alarm, and remote access through IP network. The storage costs of physical carriers, such as hard disks (HDD), digital general-purpose disks (DVDS) or network storage (NAS), are only a fraction of the cost of analog video. The use of digital video recording and archiving techniques also helps to preserve video videos permanently without loss of image quality over time. All of these factors have driven the security monitoring community to make DVR the standard for video records.
DVR类型
安全监控市场经历过多个不同的DVR发展阶段。嵌入式、混合式以及基于PC的DVR，这些系统都需要基本的视频和音频采集单元：模/数转换、压缩、回放和网络流处理。嵌入式DVR是一种独立设备，可接受模拟CCTV摄像机输入，压缩并存储在本地HDD;混合式DVR能够接受模拟CCTV和IP摄像机输入，将其作为视频源;基于PC的DVR则随硬件压缩卡或PC运行的软件压缩程序集成在安全监测站。不同模块的关键特性包括：视频输入通道数、所支持的压缩标准、录像质量、流处理和播放模式、存储容量以及系统能够同时执行的功能数量。
视频压缩技术
H.264是针对安全监控DVR视频压缩的新行业标准。相比上一代MPEG-4，甚至是MJPEG标准录像技术，H.264的优势在于具有更高的压缩比，能够为安全监控系统提供高品质图像。H.264较高的压缩比(可以达到上一代压缩技术的两倍)能够使容量扩充100%，所生成的文件尺寸更小，从而能够在固定容量的存储装置上记录更长时间的图像。此外，采用H.264压缩技术能够以非常低的码率通过网络传输高品质影像。如果没有经过高效压缩，一个多摄像机安全监控系统很快就会超出网络的可用带宽。为了延长录像时间、降低视频码率，没有采用H.264压缩技术的DVR系统不得不降低录像帧率或清晰度，从而降低了图像质量。为了保证产品的后向兼容性，许多系统仍然采用了传统的编***格式(MPEG-4和MJPEG)。但是，从当前的发展趋势看，H.264已经成为业内DVR的首要编***技术。
DVR系统需求
视频安全监控系统对于录像和显示清晰图像的要求越来越高。早期DVR的录像清晰度大多采用CIF(NTSC360×240)，数字视频质量与其所取代的模拟VCR相当。低清CIF也比较适合第一代编***技术(MJPEG/MPEG-4)，但这种技术的图像压缩比已经无法胜任高清系统的要求。当前的市场需求和发展趋势是标清(D1NTSC720×480)或“DVD质量”的视频录像。与CIF相比，标清(SD)系统每个通道的处理能力提高了4倍。
代表最新技术水平的H.264编***技术被广泛用于D1清晰度或更高清晰度的系统，以确保高效压缩比。Maxim的H.264系列处理器能够灵活设置视频清晰度，以满足不同录像系统的视频质量要求。
DVR type
The security monitoring market has experienced many different DVR development stages. Embedded, hybrid, and pc-based DVRS all require basic video and audio acquisition units: mode/number conversion, compression, playback, and network flow processing. Embedded DVR is a kind of independent device, which can accept input from analog CCTV camera, compress and store in local HDD. Hybrid DVR can accept input from analog CCTV and IP cameras as video source. A pc-based DVR is integrated with a software compressor running on a hardware compression card or PC at a security monitoring station. Different modules of the key features include: video input channel number, supported by the video compression standard, quality, flow processing and playback modes, storage capacity, as well as the system can perform the function of the number at the same time.
Video compression technology
H.264 is a new industry standard for security monitoring DVR video compression. Compared with the previous generation of mpeg-4 and even MJPEG standard video recording technology, h. 264 has the advantage of higher compression ratio, which can provide high quality images for the security monitoring system. H. 264 high compression ratio (can achieve twice the last generation of compression technique) can make the capacity expansion of 100%, the generated file size smaller, so that they can in the fixed capacity storage device record images for a longer time. In addition, h. 264 compression technology can transmit high quality images over the network at very low code rate. Without efficient compression, a multi-camera security monitoring system will soon exceed the available bandwidth of the network. In order to extend the recording time and reduce video code rate, DVR system without h. 264 compression technology has to reduce the video frame rate or sharpness, thus reducing the image quality. In order to ensure the backward compatibility of products, many systems still adopt the traditional programming *** format (mpeg-4 and MJPEG). However, according to the current development trend, h.264 has become the primary technology of DVR in the industry.
DVR system requirements
Video security monitoring system has higher and higher requirements for video recording and display of clear images. Most of the early DVR's video resolution is CIF(NTSC360 x 240), and the quality of digital video is equivalent to the analog VCR it replaces. CIF is also suitable for first generation programming (MJPEG/ mpeg-4), but the image compression ratio of this technology is no longer adequate for high definition systems. The current market demand and development trend is the video video of standard definition (D1NTSC720 * 480) or "DVD quality". The processing capacity of each channel in the standard & clearing (SD) system is four times higher than CIF.
H.264, which represents the latest technical level, is widely used in D1 definition or higher definition systems to ensure efficient compression ratios. Maxim's h.264 series processor can flexibly set video clarity to meet the video quality requirements of different video systems.
视频安全和监控领域的另一个发展趋势是全帧率录像和存储。模拟CCTV摄像机的全帧速率在NTSC制式下为30fps，PAL制式下为25fps。相对于降低帧率后的DVR设计，例如，7.5fps(NTSC制式的25%)或15fps(NTSC制式的50%)，实时视频录像系统每个通道的处理能力要求提高2～4倍。为了满足新型DVR设计的处理需求，需要一种功能强大的可升级系统架构。
随着时间的推移，当前市场上的多数视频安全监控系统采用的是模拟CCTV设备和数字式网络技术的混合架构。传统的数字设备基于早期的编***技术(MJPEG/MPEG-4)，这就要求新设备能够支持两种格式的转换。例如，采用当前MJPEG压缩算法的IP摄像机所采集的视频信号必须在DVR中重新编码为H.264格式，从而实现高效存储并充分利用网络带宽。当前的DVR设计必须接受多格式数字视频输入(MJPEG/MPEG-4/H.264)，以保护早期设备的投资。Maxim的H.264系列处理器能够在重新编码为H.264格式之前进行MJPEG和MPEG2***，支持新系统的录像和数据流处理。
Another trend in video security and surveillance is full frame rate video and storage. The full frame rate of the simulated CCTV camera is 30fps in the NTSC mode and 25fps in the PAL mode. Compared with DVR design after frame rate reduction, for example, 7.5 FPS (25% of NTSC format) or 15fps(50% of NTSC format), the processing capacity of each channel of real-time video video system is 2-4 times higher. In order to meet the processing requirements of the new DVR design, a powerful scalable system architecture is needed.
Over time, most video security monitoring systems on the market today use a hybrid architecture that simulates CCTV equipment and digital network technology. Traditional digital devices are based on early programming techniques (MJPEG/ mpeg-4), which require new devices to support conversion between two formats. For example, video signals collected by IP cameras using the current MJPEG compression algorithm must be re-encoded as h. 264 in the DVR to achieve efficient storage and make full use of network bandwidth. The current DVR design must accept multiformat digital video input (MJPEG/ mpeg-4 / h.264) to protect early device investments. Maxim's h.264 series of processors can perform MJPEG and MPEG2*** ** before recoding to h.264, supporting video and data flow processing of the new system.
