How to choose a suitable hard disk recorder (DVR)

At present, the brands and types of DVRs on the market can be said to be varied and versatile. Products with fast recording speed, large storage capacity, large compression ratio and high image clarity are everywhere. In the face of dazzling functions, we should How to identify the pros and cons, how to choose the right product? Differentiate the indicators of DVR

Video recording speed

In terms of recording speed, in fact, all DVRs are 30 pictures/second or 60 fields/second (NTSC format) in real time. Any advertisement 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 multi-channel recording is used, some DVRs use advanced image displacement detection to greatly increase the recording rate. The recording speed of the image is almost instantaneous, which is many times faster than a video recorder without image displacement detection. However, it should be noted that the image displacement detection recording refers to the full screen compression of the full screen of the camera with image displacement, instead of only compressing and recording the image displacement activity in each camera image, although the latter can also increase the recording rate, but in Europe and America. In the law, such images will not be available as evidence.

2. Storage capacity and backup

The larger the recording capacity, the better, but the most important thing is to have an interface to connect external digital storage devices to back up image data. Only when you back up frequently can you ensure that valuable images can be safely saved and easily transmission. It is unwise to have a few months of images on the internal hard drive of the machine. Once the machine is damaged, all the data will be completely lost.

3. Image clarity

The image clarity directly reflects the quality of the DVR, but from a technical point of view, the higher the definition, the larger the storage capacity, so that the user can adjust the level of clarity according to the actual situation, which is the best. Design, almost all of the products of the brands have been done.

4. Easy to operate or not

Whether the operation is easy or not ultimately determines the adaptability of the product in practical applications. More and more users hope that the equipment they use will be able to complete all functions by one button. Many manufacturers ignore the overall quality of the user's use of electrical equipment. The product is designed to have many functions, the operation is too complicated, and the result is difficult to be promoted. In order to improve this deficiency, many manufacturers are constantly improving their products, such as adopting a humanized keyboard, simplifying daily operation and use, or adding computer network interface functions, and adapting to the development trend of the network to expand the possession in the international market. rate.

Choose the DVR that works best for you

When users choose DVR, they should avoid falling into the above misunderstandings, and ignore the real advantages and disadvantages of the products; and should choose the most suitable products according to the needs of their own engineering applications, not blindly pursuing various high-tech indicators, after all, not The more functions and the higher the technicality, the more suitable for each user. The following three viewpoints are proposed for reference by engineering and end users.

1. Performance meets project requirements

When choosing a DVR, first determine where the device is going to be used. Is it a security monitoring project (such as buildings, airports, museums, etc.), or is it a bank teller project that requires high recording speed? The products used in the security monitoring project are characterized by complete functions, good network transmission function, and slow recording speed. However, through linkage with sensors and motion detection, video resources can be allocated to the most needed places. The products used in the bank teller monitoring project are characterized by high recording speed, and each channel can reach more than 20 frames. It must have real-time video, multi-channel video and audio and audio and video synchronization functions, but due to the workload in image processing. Very large, so other functions such as its network are relatively weak. Different types of DVRs should be used in different types of monitoring projects to avoid cost waste and poor operation. For example, if a device suitable for security surveillance projects is improperly planned in a bank teller project, the recording speed will not meet the user's needs. Because the bank teller project has higher requirements on computer configuration and hard disk capacity, the cost is relatively higher. To put it another way, if you use the products for the bank teller project when planning the security monitoring project, the cost will be wasted, and the security monitoring project often has the requirements of transmission and sub-control, which is the bank teller project system. Weaknesses. At the same time, it is necessary to remind everyone that the DVR is a "multi-function" device, not a "one machine" device. There are often users who want a device to solve all the problems, but in fact, the current level of computer hardware and software technology can not fully meet the requirements of users. Because the computer's bus transfer speed, CPU processing speed and hard disk burning speed are limited, unless you use a supercomputer, you can't transfer, process and burn so much data at the same time. However, the price is quite high. Users are unacceptable.

2. After stability verification

If the stability of the DVR is not enough, failure to record images at important moments will lead to many serious problems. The stability of DVR can be considered mainly from two aspects: hardware structure and software program. In view of the fact that there are many PC-based types of DVRs on the market today, the following are only examples of PC-based models:

Hardware structure

DVRs are multi-input, and the hardware can be multi-card or single-card. Sometimes in order to improve product performance, such as increasing the recording speed, multi-card mode will be adopted, but it is easy to cause conflicts between hardware. The bank teller project equipment like the above often has such problems. In general, the fewer the number of acquisition cards used, the better, because of the high integration of the single card, and the stability is better than the multi-card mode. In addition, the heat dissipation problem of the device is also a factor to be considered.

2. Software program

Software programs must be written and verified through long-term operation and operation. In particular, special attention should be paid to the stability of the hard disk. One of the key advantages of the DVR is that it does not need to constantly change the storage medium. It will constantly refresh the hard disk, clear the expired data, and save the latest data. However, some DVRs often have problems in this process, and this is often Engineering and users are the most easily overlooked. Therefore, choosing the product that has been widely used and the user reflects it well is probably the easiest way.

3. Feasibility and additional cost of adding hard disk

In general, the capacity of the DVR's own hard drive is not enough. For example, a DVR for bank teller monitoring requires a 30-day image to be stored for at least 200 hours. If an eight-way real-time DVR is used, even if the amount of image data per frame is compressed to 2K, the required hard disk capacity is at least 300GB. And it is hard to say whether the image data amount is compressed to 2K and the image quality is acceptable. Therefore, whether or not it is possible to add a hard disk to expand the storage capacity becomes an important issue. In addition, since the cost of the hard disk is still high, it is necessary to consider the cost of the subsequent additional load.

In summary, engineering companies and users should fully consider whether the performance of the equipment meets the needs when selecting the DVR. It is impossible to force all the functions to be strong; the stability of the equipment should be investigated in many ways to avoid problems during use. In order to ensure that the image storage time meets the requirements, the feasibility and convenience of adding the hard disk and the additional cost should be considered in advance. Finally, it is necessary to know the limitation of the development level of the computer software and hardware technology to the performance of the hard disk video recorder. It is judged whether the function of the product is exaggerated. In addition, based on the principle of "seeing is believing", it is recommended to buy the product that mainly looks at the image and transmission, in order to select the most suitable product among many products.