In the current video surveillance field, in addition to traditional CCTV monitoring equipment such as analog cameras and analog monitors, NetworkCamera, VideoServer and DVR are three hot words in recent years. For engineering and end users, when considering the construction of video surveillance systems, they usually face comparisons and choices among the three, especially when considering the construction of digital and networked video surveillance systems. .
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In general, the advantages and features of network cameras in terms of functional performance are obvious. It is easy for people to decide whether to use such devices according to their actual needs. But if you need to make a clear choice between the video server and the DVR, it is not an easy task for many engineers and end users. Indeed, on the surface, these two types of products have too many similarities in function and application. They all need to be used with analog cameras. They need to digitize analog video and audio signals, and the supported video image compression formats are also supported. Generally the same. After comparing with your actual needs, it seems that you can use a video server or DVR. Therefore, in many cases, the user may only make a final choice for comparing the price of the two types of products. Compared with the video server, especially the video server products of well-known foreign manufacturers, the DVR products produced by domestic manufacturers have a strong price advantage, which may be the reason why the sales of DVRs in China are much higher than the sales of video servers. one.
In fact, from a professional point of view, video servers and DVRs are two distinct products, which are related to video surveillance systems in terms of intelligence, scalability, openness, integration, reliability, application mode, and so on. There are significant differences in the overall factors of overall performance and cost. This article will analyze these different points one by one, and on this basis, briefly discuss the main advantages of network cameras, hoping to help the majority of engineers and end users to see the essential differences between the two products, so that in engineering practice Make the right choice.
Network camera, video server and DVR product overview
Network video server
Whether it is a video server (VideoServer), a video encoder (VideoDecoder), or a VideoStreamer, these names actually refer to a device that can digitize and compress analog video and audio signals and transmit them over an IP network. Among these names, "Video Encoder" and "VideoStreamer" can more accurately describe the analog/digital conversion function of the product, but it does not clearly indicate the function of its network. The "video server" describes the features of each aspect of the product more comprehensively, because most of these products are built-in WebServer, they have their own independent IP address, and can be used as a complete Web server. The main difference between them and traditional web servers is that they provide users with web services that are mainly video and audio.
The main components of the video server include analog video input interface, analog/digital converter, image compression chip, CPU and memory, network interface, serial interface and alarm input and output interface. The analog video signal received from the video input is first digitized, then compressed by the image compression chip according to the MJPEG or MPEG compression algorithm, and finally transmitted by the CPU to the browsing client on the network through the network interface. In addition, with the support of the image compression chip, the CPU can also implement intelligent functions such as motion detection, alarm event management, image overlay text or LOGO, IP address filtering, HTTPS encryption, etc., and can also provide HTTP, FTP, SMTP, SNMP. A variety of services.
Web video camera
Network cameras (NetworkCamera) are also commonly referred to as IP cameras (IPCamera) or IP cameras. They are a highly integrated product that can be thought of as a combination of a normal camera and a microcomputer, or as a combination of an analog camera and a video server.
A network camera can be functionally divided into two parts: a camera and a computer/web server. The part of the camera includes optical components such as a lens, a filter, and an image sensor, and mainly performs image acquisition and optical/electrical conversion work, that is, converts various optical signals constituting the image into electrical signals, and also performs exposure control, shutter control, and white. Common image adjustment tasks such as balance adjustment, brightness chromaticity adjustment, and backlight compensation. The structure of the computer/web server is basically the same as that of the video server, including the image compression chip, CPU and memory, network interface, and alarm input and output control interface. This part of the function is also very similar to the video server, mainly responsible for compressing the digital image and transmitting it through the network. It is also responsible for dynamic detection, alarm event management, overlay text or LOGO in the image, IP address filtering, HTTPS. Intelligent functions such as encryption, and providing various network services such as HTTP, FTP, SMTP, and SNMP.
DVR (Digital DVR)
DVR (DigitalVideoRecorder) is also commonly referred to as digital hard disk recorder. There are many kinds of such products on the market, including PC-based DVR and quasi-embedded DVR, DSP-based embedded DVR and ASIC-based embedded. DVR. Among them, the embedded DVR is gradually becoming the mainstream product in the market due to its strong advantages in stability and processing capability. Typical DSP-based embedded DVR devices mainly include analog/digital conversion, image processing and compression, CPU and memory, storage devices, peripheral drivers, network interfaces, serial interfaces and alarm interfaces. In addition, there are some products that integrate analog video split display and video switching into the board.
Some of the video signals from the front-end analog camera can be output to the normal analog monitor through the loop-through, and the other part is sent to the DSP chip for image processing and compression after analog-to-digital conversion, and then written to the memory through the CPU. Among the devices, digital video signals can also be transmitted to remote clients over the network. During video playback, the corresponding data is read by the CPU in the storage device and displayed on the analog monitor after digital/analog conversion. In addition, the CPU needs to process the control commands of various peripherals and perform corresponding operations.
With the increasing popularity of network video surveillance, a new DVR product has appeared on the market, specifically for recording digital video signals from network cameras or video servers. This product is often called NVR (NetworkVideoRecorder).
Video server VSDVR
Today, the industry generally believes that video surveillance systems have evolved to the third generation. The first generation video surveillance system refers to the traditional CCTV system using pure analog technology represented by VCR (VideoCassetteRecorders); the second generation is represented by DVR (DigitalVideoRecorder), part of the video surveillance system using digital technology; The generation system refers to the all-digital, networked video surveillance system represented by network cameras and video servers, which is currently booming, also known as IP surveillance systems.
It can be seen that the DVR is a video surveillance technology of the previous generation compared with the video server.
However, because there are many functional similarities between the two, many users do not understand this kind of division. Next, we will analyze and compare the main differences between the video server and the DVR from multiple parties, so that users can Better understand the difference between the two types of products.
Distributed intelligence VS centralized processing
Regardless of the physical location of the video server, it is a front-end device in the video surveillance system, and the DVR belongs to the back-end device, which is actually one of the most important differences between the video server and the DVR. Such a statement may not be understood by many people, because in actual applications, many video servers will be concentrated in the monitoring center's computer room like the DVR. From the physical point of view, they are also at the back end of the monitoring system. But in fact, in the video surveillance system, the division of the front-end device and the back-end device is not based on the physical location of the device, but is divided according to the function of the device. In general, the front-end equipment is mainly responsible for image and sound collection and preliminary processing, while the back-end equipment is mainly responsible for the final processing of audio and video data and equipment management and maintenance, including image storage, data archiving management, alarm event processing, human-computer interaction, and system. Management and so on. Of course, most video servers and webcams on the market today have image caching capabilities, and some also support the connection of additional storage devices, but this is not used for the final processing of data.
Both the video server and the DVR are smart devices that have the ability to analyze and process video images, enabling highly intelligent functions such as motion detection (VMD), alarm management, and even population statistics and license plate recognition. However, since the video server belongs to the front-end device, it means that the system using the video server deploys the intelligence to the front end of the system, thus constructing a video surveillance system with distributed intelligence. So the video server itself can decide when to send the video, at what frame rate and resolution to send, and when to which security personnel should be alerted to alert them to the monitoring screen or take appropriate action. That is to say, the video server at the front end shares part of the work tasks of the back-end device. Before sending the data to the back-end device, it first passes its own judgment, thus filtering out a lot of useless information, only some important The information is sent to the relevant equipment and personnel. This greatly reduces the system's need for transport network, storage space, and back-end device processing capabilities. In this case, the intelligence and processing power of the system increases as the number of front-end devices increases, and does not have much impact on the processing power of the back-end devices.
Contrary to this, regardless of whether the content in the monitoring screen is valuable to the user, the DVR must collect all the video information to the back end, and then uniformly call the computing resources for processing and analysis. The content that does not contain any user interest should be discarded, and the valuable processing power of the device has been wasted. This waste will become more serious when a DVR needs to process multiple video images. In addition, the same DVR also needs to simultaneously process image storage and archiving, video playback, response and drive external devices and other work. When the number of processed images increases, its processing power is extremely limited. May affect the overall performance of the system.
The ability to scale on demand is another important advantage that can be achieved with video servers that are part of a front-end device. Users can increase the number of video surveillance channels required each time according to their own needs. There is no limit to the number of each increase. It can be 1 channel, 3 channels, 7 channels, or 100 channels or even 1000 channels. For DVR, you can only increase the number of fixed channels at a time. Suppose the user has already set up a 16-channel DVR. If you need to add another camera, you may have to purchase another 8-way or 16-way. DVR equipment, which may cause unnecessary waste.
Open platform VS proprietary technology
At present, DVR products do not have a unified standard in the industry. Most manufacturers adopt their own proprietary technologies in hardware and software. These technologies involve embedded systems, data communication, image processing, data storage and even compression formats. surface.
This kind of "black box" approach makes it difficult for the manufacturers' equipment to be compatible with each other. When the user selects a certain manufacturer's equipment, the subsequent optional range becomes very small, and even the equipment of a specific supplier can only be continuously purchased. . This means that users will be at a distinct disadvantage when negotiating prices. In addition, if the company closes or changes its business domain, the user's equipment will not be professionally maintained or even used. If this happens, in addition to economic losses, some historical data will be irreparable, and the losses caused by this will not be estimated.
Generally speaking, video server products adopt an open architecture, and adopt standard industry standard technologies in operating systems, data communication and image compression. For example, the video server of an internationally renowned manufacturer adopts the standard Linux 2.4 as the embedded operating system kernel, and adopts the standard TCP/IP as the communication protocol. The image compression format adopts MJPEG and MPEG-4 (Part 2: ISO/IEC). -2, Profiles: ASPandSP), and is 100% compatible with international standards. All of its development interfaces are based on the standard HTTP protocol and provide download and development support to all video application developers for free. Open architecture and standards-based protocols make video server products "transparent", users choose a brand of video server in the project, and then choose a price/performance ratio from a large number of industry-standard server hardware and storage devices when the project is expanded. The highest product is added to the system, which shows that the device has strong compatibility.
In addition, 100% image compression in line with international standards means that in addition to dedicated playback software, users can use a variety of standard playback software for video playback. After 10, 20 or even 50 years, the user's historical image data can also be played normally.
Low TCOvs low single cost
From the perspective of single-channel cost, the video server products of well-known manufacturers are usually much higher than the DVR products produced by domestic manufacturers. This is a practical matter, but to some extent it is also a reasonable phenomenon: a 16-channel DVR, Its computing resources are evenly distributed to 16 channels of video; while a single channel video server, the same or even higher computing resources are only available for 1 channel of video. In addition, tariffs, labor costs and intellectual property factors are also important factors in the price of foreign products. However, users should be concerned not only with one-way costs, but also with total cost of ownership (TCO, TotalCostofOwnership). TCO covers a range of costs including system hardware, software, security, maintenance, training, upgrades, extensions, and technical support services, as well as factors such as infrastructure efficiency and the impact of system usage on business processes.
For large video surveillance systems, the overall cost of the video server-based hardware (including cameras, cables, and video storage) is usually comparable to the hardware cost of the DVR-based surveillance system. Considering the cost of the system, then IP technology is adopted. The advantages of a video server system are obvious, because the cost of building, maintaining, upgrading, and extending an IP-based infrastructure is much less than that of a coaxial cable-based infrastructure. In addition, because the application and storage capabilities of the video server-based system backend can use industry-standard, open-standard-based server hardware, it is not necessary to use a dedicated hardware platform as in a DVR system. This is especially important for some large systems, where storage and server hardware typically account for a significant portion of the overall cost, while using video servers can significantly reduce the cost of storage and server hardware device management and acquisition. The cost savings also come from the infrastructure used by the video server. In addition to carrying video surveillance services, IP networks can also carry other types of applications in the enterprise, such as the Internet, LAN, and wireless networks, compared with traditional coaxial cables or optical fibers dedicated to video surveillance. The construction cost of the IP network is very low.
Seamless integration VS limited customization
Large-scale video surveillance systems usually involve the customization of back-end monitoring software and integration with other security systems. Therefore, the video surveillance equipment used in the system usually needs to provide certain secondary development and integration capabilities. For existing DVR products, it is generally provided with dedicated software, and rarely provides secondary development support. Even if it supports secondary development, it provides development interfaces and supporting tools (such as SDK development kits, Test tools, management and maintenance tools, development support services, etc. are relatively small, so it is difficult to achieve complete control and free customization of the equipment.
Video server products from well-known manufacturers generally provide more comprehensive secondary development support. Generally, they have a completely unified secondary development interface based on the HTTP universal protocol. Developers only need to develop for a class of devices, so that their software can support a large number of network video products. In addition, users can provide free detailed API descriptions and parameter descriptions, as well as various SDK development kits, testing tools (AVC), and management tools (ACMSDK). It also supports a variety of embedded applications and embedded scripts, allowing developers to further deepen their control and customization of these products for seamless integration with other systems.
Multi-family win-win vs exclusive
As mentioned in the previous article, DVR products are actually a "black box" type of solution, from hardware to software, a variety of proprietary technologies, thus providing system integrators and software developers. The space available is very limited, and end users are not free to choose from a wide range of equipment suppliers. This is obviously not a virtuous cycle of a win-win situation.
The video server is an open product, standardized hardware and interfaces, and its focus on front-end capabilities, enabling it to hand over back-end business areas such as software development, data storage and management to specialized companies in these areas. System integrators can obtain high added value through software customization. Software developers can develop various industry markets by developing common software based on these products. IT product suppliers and solution providers can implement standard server equipment. Storage and network equipment and sales of the solution, the end users can get more, more cost-effective products and solutions. It can be seen that compared with DVR, video server is easier to construct a market environment with multiple win-win and benign development.
Conclusion
This article makes a simple comparison and analysis of video server and DVR. It is not difficult to see that the video server has many features that are better than DVR. Of course, this does not mean that all users should immediately choose the video server after leaving the DVR product, or choose according to their actual needs. In general, the video server is suitable for building a video surveillance system with distributed intelligence, large-scale, and widely distributed monitoring points. The DVR is suitable for building smaller, less intelligent, and more distributed monitoring points. Small video surveillance system.
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