Hikvision hard disk video recorder recording effect description

DVR is Digital Video Recorder (also called: Personal video recorder or PVR) - digital video recorder or digital hard disk video recorder, which we are accustomed to call hard disk video recorder.

It is a computer system for image storage and processing. It has the functions of long-term video recording, recording, remote monitoring and control of images/voices. DVR integrates video recorders, screen splitters, and PTZ lenses. The five functions of control, alarm control, and network transmission are integrated into one device. One device can replace the functions of a large number of devices in the analog monitoring system, and it gradually has an advantage in price.

DVR uses digital recording technology, which is far superior to analog monitoring equipment in terms of image processing, image storage, retrieval, backup, network transmission, remote control, etc. DVR represents the evolution of TV monitoring systems. Development direction, it is the first choice product for TV monitoring systems currently on the market.

The popular products on the market include PC platform DVR and embedded DVR. Embedded DVR has "professional" advantages in terms of stability, reliability, ease of use, etc. Embedded DVR will gradually encroach on The market for PC platform DVR. PC platform DVR has advantages in versatility and scalability. It can still play the role of managing the host in the network video surveillance system and still has its own market share.

Due to price, performance and other reasons, DVR products in the domestic market are mainly products from Greater China, including Taiwan, and South Korea. Mainland enterprises have the advantage of being "Made in China". However, in terms of technology, it almost completely relies on foreign technological development, and has not mastered the key technologies for the development of core chips and embedded motherboards. The company's technological innovation capabilities are poor. Taiwan and neighboring South Korea are stronger than mainland companies in this regard.

At present, many foreign companies have invested in the development of multi-channel MPEG-II, MPEG-4 compression chips, and wavelet image compression chips. The emergence and application of new compression chips will enable digital network video surveillance. Moving towards a new era.

At the same time, as the capacity of storage devices continues to increase, prices continue to decrease, new storage technologies develop, all-digital and high-definition cameras continue to improve, and high-definition image standard products will be put into use. market and become the new favorite of digital network video surveillance.

In addition, when developing new products, companies should also pay attention to establishing unified standards through industry associations so that products from different companies can truly share data through the network, and should be integrated with building intelligence systems as much as possible. The other subsystems in the system are seamlessly connected to achieve unified management and control of the building system.

The hardware of the DVR system mainly consists of CPU, memory, motherboard, graphics card, video capture card, chassis, power supply, hard disk, connecting cables, etc. Let us analyze these components from a systems perspective stability and reliability.

1. How to choose a suitable DVR?

The DVR brands and types currently on the market can be said to be diverse and dazzling, boasting fast recording speed, large storage capacity, and large compression ratio. , Products with high image definition abound. Faced with the dazzling functions, how should we distinguish their advantages and disadvantages and how to choose the product that suits us? To distinguish the advantages and disadvantages of digital video recorders (DVR), you can judge from important performances such as recording rate, storage capacity, picture clarity, and operation and usage methods. However, there are many misunderstandings in the market regarding the comparison of these points. Many users blindly pursue fast speed, large capacity, and high definition, but they do not know that in fact these three indicators are mutually restrictive, and it is impossible to require all three to achieve the best; and whether the operation is easy to use is often considered by most projects. The company's equipment selectors ignored it and didn't discover it until the installation process, which wasted a lot of time.

Indicators that distinguish the advantages and disadvantages of DVRs

1. Recording speed. In terms of recording speed, in fact, all DVRs are 30 frames/second or 60 frames/second in real-time. (ntsc format), any advertising that exceeds this indicator is unrealistic. If 16 channels of images are recorded at the same time, the rate of each channel is only 30/16 frames per second or 60/16 fields per second. When recording multiple channels, some DVRs use advanced image displacement detection methods to greatly increase the recording rate. The recording speed of images is actually almost real-time, which is many times faster than recorders without image displacement detection function. However, it should be noted that image displacement detection recording refers to full-frame compression and recording of the entire camera frame with image displacement, rather than only compression and recording of the portion of each camera image with image displacement activity. Although the latter can also increase the recording rate, in Europe and the United States, Under the law, such images cannot be used as evidence in court.

2. The larger the storage capacity and backup recording capacity, the better. But the most important thing is to have an interface to connect an external digital storage device to back up the image data. Only by backing up frequently can the value be guaranteed. Images can be safely saved and easily transferred. It is unwise to store several months of images on the machine's internal hard drive. Once the machine is damaged, all data will be completely lost.

3. Image clarity The level of image clarity directly reflects the quality of the DVR. However, from a technical perspective, the higher the resolution, the greater the storage capacity occupied, so users can adjust the resolution according to the actual situation. The best design is to adjust the level of clarity. This is something that almost all brands of products have done.

4. Whether it is easy to operate or not. Whether it is easy to operate and use ultimately determines the adaptability of the product in practical applications. More and more users hope that the equipment they use can complete all functions with the press of a button. Many manufacturers ignore the overall quality of electrical equipment used by users and design products with multiple functions and overly complicated operations, making it difficult to promote them. In order to improve this shortcoming, many manufacturers are constantly improving their products, such as using humanized keyboards to simplify daily operations, or adding computer network interface functions, and complying with the trend of network development, etc., in order to expand their share in the international market Rate. Choose the most suitable DVR for you. When choosing a DVR, users should avoid falling into some of the above misunderstandings and ignore the real advantages and disadvantages of the product; and should choose the most suitable product according to the needs of their actual engineering applications, and do not blindly pursue various After all, high technical indicators do not mean that the more functions and higher the technical level, the more suitable it is for every user.

The following three options are proposed for reference by engineering contractors and end users.

1. The performance meets the project requirements. When choosing a DVR, you should first determine where the equipment will be used? Is it a security monitoring project (such as a building, airport, museum, etc.), or a bank teller project that requires high video recording speed? Products used in security monitoring projects are characterized by complete functions, good network transmission capabilities, and slow recording speed. However, through linkage with sensors and motion detection, recording resources can be allocated to where they are most needed. The products used in bank teller monitoring projects are characterized by high recording speed, each channel can reach more than 20 frames, and must have the functions of real-time recording, multi-channel video and audio, and audio and video synchronization. However, due to the workload of image processing It is very large, so its network and other functions are relatively weak. Different types of DVRs should be used in different types of monitoring projects to avoid wasting costs and ineffective operation. For example, if the equipment suitable for security monitoring projects is not properly planned in the bank teller project, the recording speed will not be able to meet the needs of users. Since the bank teller project has higher requirements on computer configuration and hard disk capacity, the cost has also increased relatively. To put it another way, if you use products suitable for bank teller projects when planning security monitoring projects, the cost will be wasted, and security monitoring projects often have transmission and sub-control requirements, which is exactly what the bank teller project system needs. Weaknesses. At the same time, it is necessary to remind everyone that DVR is a "one machine with multiple functions" equipment, not a "one machine with all functions" equipment. There are often users who hope that one device can solve all problems, but in fact, the current technical level of computer software and hardware is still basically unable to fully meet user requirements. Because the computer's bus transmission speed, CPU processing speed and hard disk burning speed are limited, unless a supercomputer is used, it is impossible to transmit, process and burn so much data at the same time. However, the price spent is quite high. This is unacceptable to users.

2. Stability verification If the DVR is not stable enough and fails to record images at important moments, it will cause many serious problems. The stability of DVR can mainly be considered from two aspects: hardware structure and software program. Since most of the types of DVRs currently on the market are PC-based, the following only gives examples of PC-based models:

1. Hardware structure: DVRs all have multiple inputs, and the hardware can use multiple Card or single card method. Sometimes in order to improve product performance, such as increasing recording speed, a multi-card method is used. However, this can easily cause conflicts between hardware. Such problems often occur with the bank teller project equipment mentioned above. Generally speaking, the fewer capture cards used, the better, because the single-card method has higher integration and is more stable than the multi-card method. In addition, the heat dissipation of the equipment is also a factor that needs to be considered.

2. Software program: The quality of the software program must be verified through long-term operation and operation. Special attention should be paid to the stability of the hard disk's recycling. One of the key advantages of DVR is that there is no need to constantly replace storage media. It will constantly refresh the hard disk, clear out expired data, and save the latest data. However, some DVRs often have problems when performing this processing, and this is often the case. It is most easily ignored by engineers and users. Therefore, choosing a product that has been widely used and has good user feedback may be the easiest way.

3. The feasibility and additional cost of adding a hard drive. Generally speaking, the capacity of the hard drive that comes with the DVR is not enough. For example, a DVR used for bank teller monitoring is required to save images for 30 days, and the video length is at least 200 hours. If an eight-channel real-time DVR is used, even if the image data volume of each frame is compressed to 2K, the required hard disk capacity is at least 300GB. , and if the image data is compressed to 2k, it is difficult to say whether the image quality is acceptable. Therefore, whether it is possible to add a hard disk to expand storage capacity has become a very important issue.

In addition, since the cost of hard drives is still high, whether the subsequent additional costs can be afforded must also be taken into consideration. Conclusion In summary, when engineering companies and users choose DVRs, they must fully consider whether the performance of the equipment just meets their needs. They cannot insist that all functions are powerful; the stability of the equipment must be inspected in many aspects to avoid problems during use. problem; and in order to ensure that the image storage time meets the requirements, the feasibility and convenience of adding a hard disk, as well as the additional cost, should be considered in advance; finally, it is necessary to know the limitations of the development level of computer software and hardware technology on the performance of the hard disk video recorder in order to be clear and Correctly judge whether the function of the product has been exaggerated. In addition, based on the principle of "seeing is believing", it is recommended that buyers pay more attention to the performance of the product in terms of image and transmission, so that they can choose the product that best suits them among many products.

2. Classification and selection of digital hard disk video recorders

The wide application of hard disk video recorders has transformed the surveillance industry from a traditional industry into an emerging IT industry. The characteristics of the IT industry will gradually be reflected in the monitoring industry from now on: products are constantly being updated and developed, market life cycles are shortened, product service life is lengthened, maintenance costs are reduced, and product prices are also constantly falling, etc. At present, there are hundreds of brands of DVR products on the market in the security industry. These products have various compositions and similar performances. This article attempts to classify and compare DVR products from the perspective of product selection. The rapid development of digital image products in the security field is mainly based on the following points in terms of technology. First, the capacity of a single hard drive doubles every year, while the price drops by half; second, chip technology develops rapidly, and digital image products will gradually enter various fields. As the market expands, investment in research and development will increase; third, broadband technology The development of the Internet has brought new networking needs. In addition, from a market perspective, the demand for high-performance monitoring products from banks and other security systems is increasing. After entering the customs, banks will further reduce staff and increase efficiency, and the demand for products suitable for their management will also further increase. If there is demand, there will be products. Competition, there will be development if there is competition.

3. Applicable places for various products

PC-type DVR is suitable for applications that require more system functions and require further integration of other systems. This application environment is the best. There are people on duty, the installation is relatively centralized, and the usage of a single system is not easy to be excessive. PC-type DVR products will exist for a long time, especially in some new application areas or when new image technologies are required.

Embedded and hardware-based DVRs are particularly suitable for large-volume system applications. Regardless of analysis from various aspects such as use, maintenance, repair, and price, embedded systems will become the mainstream of DVR products. However, embedded systems will become the mainstream of DVR products. The widespread use of DVRs still requires a process. DVRs of various image compression methods 1. mpeg1 and mpeg2 are suitable for long-term recording with audio and 25 frames per second requirements. mpeg1 is 352 x 288 format, mpeg2 can have 576 x 352, 704 x 576, etc., from vcd to super The difference between different formats from vcd to dvd; mpeg1 has a smaller data volume, while mpeg2 has a larger data volume. When mpeg2 is used for long-term video recording, the hard disk cost is too large, but the resolution is higher. Suitable for long-term recording with audio and 25 frames per second requirements, mpeg1 is 352 x 288 format, mpeg2 can have 576 x 352, 704 x 576, etc., the difference between different formats from vcd to super vcd to dvd; mpeg1 data The amount of data is small, and the amount of mpeg2 data is large. When mpeg2 is used for long-term video recording, the hard disk cost is too large, but the resolution is higher. 2.jpeg and m-jpeg dvr can be used in places that only need to record a few frames per second, such as traffic security monitoring, etc. 3.h.261 and h.263 are suitable for video conferencing and image transmission with medium or lower quality. 4. Wavelet method can be used in some independent security systems. In other aspects, its performance is improved compared to previous products. However, since it is not an international standard, it is not recommended to be applied on a large scale. 5.mpeg4, especially some products called mpeg4. Some products can indeed save hard disks in applications and can be used in some independent systems. However, you should be cautious when selecting them in a system such as bank tellers, because the compression method of such products cannot If it is truly compatible with national defense standards, it will definitely face rapid obsolescence in the future. Especially for some products called mpeg4, some products can indeed save hard disks in applications and can be used in some independent systems. However, you should be cautious when choosing a system such as bank tellers, because the compression method of such products cannot be truly compatible with national defense. Standard compatibility will definitely face rapid elimination in the future.

IV. Principles for Selection of Hard Disk Video Recorders

End Users

1. Users should gradually establish a mature consumption mentality when choosing products. In today's technological development, In a rapid environment, we should abandon the mentality of pursuing perfect products and establish the mentality of pursuing perfect applications. Perfect applications include: products that meet user needs, no need to pay additional management fees and maintenance costs, products that can be used for a long time, products with high reliability, long-term warranty guaranteed and low cost.

2. Users must first clarify their own needs. They should not consider too much functions that are not yet in demand. As long as the product has extended functions, they can get a good product cost-effectiveness and face the future at the same time. The development will not be wasted because the functions previously equipped cannot keep up with the development of new technologies. When selecting products in large quantities and in a systematic manner (such as bank tellers, ATMs, etc.), you must choose standardized products and products that adopt international standard image compression methods. Otherwise, it will be impossible to establish a unified image exchange platform and monitor all levels. The system is managed online. Such standards include jpeg, h.263, h.261, mpeg1, mpeg2, etc. In the bank teller system, it is recommended to use mpeg1 or mpeg2, and mpeg4 with caution (preferably in the second half of 2003).

Engineering contractors

1. Engineering contractors should have an objective understanding of digital image products and must not arbitrarily exaggerate the performance of digital products.

2. Carefully analyze user needs to ensure that the most basic user needs are met. Some functions that are dispensable or needed in the future should be eliminated as much as possible, but extended interfaces should be retained.

3. We must seriously consider the maintenance service system for end users, and we must not put all the risks of maintenance on ourselves.

5. Key items for choosing DVR

Sharpness In image equipment using analog technology, the evaluation of images is usually expressed in terms of clarity, and there is only one metric. That is, TV lines, the higher the number of lines, the clearer the image (for example, 400 lines is the definition of DVD, 300 lines is the definition of S-VCD, and 250 lines is the definition of VCD). After using digital technology to compress and decompress images, the image evaluation is completely different. Its measurement standards mainly include two aspects: on the one hand, image format refers to how many pixels an image is composed of. International The standard is calculated by the product of horizontal and vertical pixels. The most common image formats are: 176 x 144 (qcif), 352 x 288 (cif), 352 x 576, 704 x 576 (fcif). We The VCD used at home uses the 352 x 288 (cif) image format for digital processing and compression. On the other hand, for the same image format, due to different digital compression standards or different amounts of compressed data, the image effects observed by the naked eye are also different. This is what we often call image quality. Under the same image format, compression Relatively small, the larger the amount of data. The larger the amount of data, the clearer the image and the less "mosaic" phenomenon. On the contrary, the worse the image, the more "mosaic" phenomenon. However, there is currently no unified standard in the world that can simply and clearly explain the difference between different image qualities. For professionals, they can judge based on the different international digital compression standards applied to the product and the actual compressed data stream and other indicators, such as vcd For professionals to evaluate the image, this is an image using the mpeg1 compression method, in the 352*288 (cif) format, with a 1.15mbps data stream (1.15m bits of data per second). We can also understand the format and image quality from another aspect. Measuring the clarity of still images (such as 330 lines, 480 lines, etc.) in analog image tests is equivalent to measuring the clarity of moving images, while in digital images The medium format can only represent the clarity of still images, while the image quality (equal to the compression ratio and image data volume) represents the basis for evaluating moving images. For example, under a certain image format and quality, still images can reach 250 lines, but for moving images, because the bit rate (amount of data per second) is too low, it can only reach 100 lines. When selecting a product, first select the image format. Essentially, the higher the format, the greater the amount of image data, the larger the hard disk that is required, and the higher the cost of use. As far as the current hard disk situation is concerned, 352*288 (cif) Images in format (vcd format) will have an advantage in future applications. The resolution of still images in this format is 220~250 lines, which is equivalent to that of traditional video recorders. The image quality is standard VCD. The reference bit rate is 1.15m/s (1.15m bits of data per second), which is equivalent to each frame. The image is 5.7k. Almost all DVR products used by bank tellers are changed and improved based on this image quality and format. In short, when using the human eye to observe and judge the clarity of an image, you should first determine the format and bit rate; secondly, you must analyze and compare the image in a full-screen display.

The lifespan of hard disks. Hard disks have three reliability indicators that should be paid special attention to in DVR applications: The first is mtbf (mean time between failures). The manufacturer gives an indicator of 300,000 to 500,000 hours, which means The working life of the hard drive is more than 30 years; the second is the annual defective rate (arr), the indicator given by the manufacturer is generally less than 1~2%, this indicator indicates that 1~2% of the hard drives may need repair every year; the third is For the start/stop cycle, the manufacturer points out that the general minimum value is 30,000 to 50,000 times, which means that the hard disk can only start and work 30,000 to 50,000 times. If it is started once a day, the life of the hard disk is 4 to 7 years.

Manufacturers and engineering companies fully study these three points when setting up DVRs. In addition, when selecting hard drives, users should try their best to choose mainstream, low-speed hard drives, and at the same time, they should choose hard drives with a nationwide joint warranty and a three-year warranty through formal channels. Full-duplex (over-recording, side-playing) When choosing hard disk video recording for bank teller systems, be sure to choose one that can record images at various resolutions (different formats and bit rates) within the entire hard disk space that stores images. Products that can achieve full duplex. There are two reasons: First, it can be full-duplex within the entire hard disk, which is a basis for DVR products to be connected. Only with the full-duplex function of the entire hard disk space can the normal recording of the front end be not affected. View any previously recorded images on your hard drive. Second, some DVRs using mpeg2 can only perform full-duplex (recording and playback at the same time) at low definition. What they can record and play back at high definition is slow-motion images. Currently, considering the cost of the hard disk, the only option is to use Low definition. However, the capacity of hard drives doubles every year, and the price drops by half. In the future, you can replace the expansion hard drive with a higher definition. However, such products cannot guarantee full duplex at high definition and can only stay at low definition. Video recording and networking. Multi-channel and single-channel In bank teller system applications, most products with synchronized audio using mpeg compression are used. Among these products, there are 4-channel, 8-channel, 16-channel PC models, etc. Multi-channel PC-type products appear to be highly integrated, easy to debug and use, but in fact they have problems of poor reliability and high maintenance risks. Multi-channel allocation requires more hard drives, larger power supplies, and taller boards, all of which are concentrated in one chassis. Failure of any one part (especially the hard drive) will cause the entire machine to stop working. This will inevitably increase the risks for banks and increase the maintenance costs and risks of engineering companies. Most of the embedded products are single-channel one-to-one products. There are also two 4-channel products. The first one is essentially a single-channel DVR with a built-in 4-picture splitter. This product can record and Displays a single or 4-channel image, but only two channels of audio. The problem with this product is that the maximum resolution of a single-channel digitally recorded image is less than 400 lines (generally 350 lines). If recorded in a four-channel split mode, each The resolution of the image is below 200 lines (usually 180 lines), which cannot meet the requirements of teller system monitoring. The country's first digital hard disk video recorder standard has been officially implemented in Shanghai (mandatory standard) requiring the resolution of a single channel to be greater than or equal to 220 lines. Therefore, this type of four-channel embedded hard disk video recorder will soon be eliminated. The other is embedded video recording that uses four independent channels to record images, which is equivalent to four single-channel machines. It also integrates four-screen split display and single-channel display. The playback resolution of each channel is more than 220 lines. Four channels of image processing are performed in parallel. If a certain device or a hard drive in the machine fails, the other three channels can still work normally.

DVR networking The networking application of DVR products is a direction for the development of DVR products. The current stage can only be said to be a brewing stage. 1. In terms of network communication methods, there are telephone line dial-up, dedicated line, isdn, e1, adsl, wired communication, professional broadband network, etc. Before choosing, you must first determine the user's demand for clarity and frame number. You must have A certain degree of foresight, because the development of broadband networks is very rapid, improper selection will cause waste. Secondly, we should try our best to use a monthly fee-based communication method to ensure that the system operates normally under various circumstances. For example, if the dial-up method is used, each communication will be billed, and the cost of use cannot be controlled. Since the amount of image data is generally large, in addition According to market and technology development trends, it is recommended to use broadband for networking (even if the implementation has to be postponed for half a year or one year). Such as adsl, cable communication, professional broadband network, only in this way can we leave room for the future development of the system. 2. Judging from the product type, PC-type products can generally be connected to the Internet very conveniently, and can be used in many independent applications and situations that do not have high requirements for image transmission. There are two ways of networking for embedded products. The first is external networking. Many embedded DVR products themselves do not have a networking interface. The networking distributes the DVR analog video output all the way to a dedicated networking device (referred to as Gateway), the gateway re-compresses the analog video into a digital image, and then transmits it through the network. In this way, the clarity of the image will drop significantly (because of two analog-to-digital conversions), and because there are two sets The cost of image compression devices is relatively high. Some products install an external gateway in a chassis. You should understand this clearly when choosing. In the second method, the gateway can be external or built-in. Different from the first method, this type of gateway receives the image data in the DVR hard disk and transmits it directly from the network, so its clarity is different from that of The original resolution of the DVD is the same. Since the gateway only performs transmission, the cost is lower.

Motion detection 1. Motion detection is a very good function in DVD products. It can save the installation of alarms and save hard disks, but some applications should pay attention to the effect. 2. There must be lighting when using it at night. Bank teller monitoring should not use motion detection to save hard drives, and images during working hours should not be missing frames (regardless of whether there are people or not).

3. When monitoring ATM automatic teller machines, if motion detection video is used, it will cause a large number of false recordings. This not only wastes the hard disk, but also when a case occurs, security personnel have to spend a lot of time checking the useless false recordings. image.

From an economic perspective, the use of any product should be considered from two aspects. The first aspect is the cost of upfront investment and long-term use? The second aspect is what is the maintenance cost of after-sales service?