How Do I Choose the Best Digital Video Recorder?

Digital Video Recorder (DVR) is a digital video recorder. Compared with the traditional analog video recorder, it uses hard disk video recording, so it is often called a hard disk video recorder or DVR.

DVR

Digital Video Recorder (DVR), that is,

The main functions of the DVR include: monitoring function, recording function, playback function, alarm function, control function, network function, password authorization function and work schedule function. It also contains the following features:

The outstanding features of hard disk video recorders are reflected in the following aspects:
1. Achieved digital high-fidelity storage of analog programs. The widely distributed and personally collected analog audio and video programs can be recorded and stored in an advanced digital manner. One recording and repeated playback will not cause any degradation in quality.
2. Comprehensive input and output interface provides antenna / TV cable, AV terminal, S terminal input interface and AV terminal, S terminal output interface. It can record almost all TV programs and signals output by other players and cameras, and can be easily connected with other audiovisual equipment.
3. Multiple optional image recording levels For the same program source, three image quality recording levels of high, medium and low are provided. When the highest level is selected, the quality of the produced image is close to that of DVD.
4. Large-capacity long-term program storage, strong scalability, users can choose 20.4GB, 40GB or larger hard disk for program storage. Based on the 20.4GB capacity, the relationship between the recordable program time at the selected bit rate is shown in the following table:
Bit rate (Mbps) Recordable program time (hours) 6 7 4 10 2 20 1.15 38
5. With advanced Timeshifting function. When you have to interrupt watching TV programs, users only need to press the Timeshifting key, and the programs starting from the moment of interrupted watching will be automatically saved. After the user has finished processing the transaction Watch the show from where it left off without any pause.
6. Perfect schedule recording / playback function. Users can freely set options such as the start time and duration of recording / playing programs. Through the editing and combination of the reserved program list, various intermittent TV programs can be systematically recorded, including TV series.
7. Powerful network information Household appliances center users can enjoy a wealth of online information through the network communication interface, using a DVR tailored web browser, equipped with corresponding network resources.
8. Provide a convenient way to manage recorded programs. Users can organize and categorize recorded programs according to recording time, program types, etc., and set bookmarks at their favorite locations.
9.Provide the way you want to play. Due to the fast and random storage of the hard disk, you can enjoy more and more flexible tricks than the current DVD player when enjoying recorded and currently recorded programs. The image is smoother,

System processor: industrial-grade embedded micro

The DVR brands and types appearing on the market can be said to be diverse and diverse, with products featuring fast video speeds, large storage capacity, large compression ratios, and high-resolution images abound. In the face of dizzying features, how should we Identify the advantages and disadvantages, how to choose the product that suits you?

1.Recording speed

As for the recording rate, in fact, all DVRs are 30 frames per second or 60 fields per second (NTSC format) under real-time conditions. Any advertisement that exceeds this index is impractical. 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 image recording speed is practically real-time, many times faster than a video recorder without image displacement detection. However, it should be noted that the image displacement detection video refers to the full-frame compression recording of the full image of the camera with image displacement, rather than the compression and recording of the part of each camera image that has image displacement activity. Although the latter can also increase the recording rate, In 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 to an external digital storage device to back up the image data. Only frequent backups can ensure that valuable images can be safely saved and convenient. transmission. It is unwise to store the images of several months on the internal hard disk of the machine. Once the machine is damaged, all the data will be completely lost.

3.Image clarity

The sharpness of the image directly reflects the quality of the DVR, but technically speaking, the higher the sharpness, the larger the storage capacity occupied. Therefore, it is best for users to adjust the sharpness according to the actual situation. Design, this has been done by almost all brands.

4, easy to operate or not

The ease of operation ultimately determines the adaptability of the product in practical applications. More and more users hope that the equipment they use is best to complete all functions by pressing a key. Many manufacturers ignore the overall quality of electrical equipment used by users. The products are designed with many functions and too complicated operations, and the results are difficult to be promoted. In order to improve this deficiency, many manufacturers are constantly improving their products, such as using humanized keyboards, simplifying daily operation and use, or adding computer network interface functions, and conforming to the trend of network development, in order to expand their market share in the international market. rate.

DVR is a direct-to-disk recording system, using high-capacity hard disk recording

The main purpose of hard disk video recorders is to transfer images from front-end equipment (such as cameras)

A. Test using a unified video standard signal source

In the 80's and 90's, hard disk video recorders entered various developments, and various compression methods appeared constantly, which made people dazzled. The quality of the image was even more irrelevant. The biggest problem was that there was no unified video test signal source. Everyone did not compete on the same starting line. The hard disk video recorder records and processes the video signal output by the camera. Finally, the output video signal is displayed on the monitor. The video standard test signal source should be the same signal source of the hard disk video recorder with different compression methods. In this way, the problem is simple.

B. Test system framework diagram

Computer monitor Computer-based video analysis software VGA monitor to compare static standard video signals DVR hard disk recorder (multiple) to be tested Visual signals to be measured Visual comparison Video monitor Analyzer A Monitor B Standard video signal

PC DVR

1. Take Linux as the operating interface

The fierce competition between Windows and Linux operating platforms in the IT industry has also been extended to the security industry. Linux is an operating environment that can be used by multiple people, allowing multiple users to use the resources of the computer host at the same time. Linux provides a complete multi-user Multiuser, multi-tasking Multitasking and multi-stroke Multiprocessing environment, which can be downloaded and used on the Internet. Because its original program code (Source Code) is public, it can be developed and modified arbitrarily, so users of Linux do not need to worry about the lack of needed applications, which accelerates the speed of R & D, and the system itself and most applications It's free, allowing developers to save a lot of R & D costs. In addition, Linux, which has lower hardware requirements, allows users to save more hardware costs and reduce overall product costs. With the prevalence of the Internet, more and more people use Linux worldwide. It has also attracted countless developers to invest in improving the core, developing application software, and hardware peripheral drivers. As a result, the functions and integrity of Linux have expanded and become more diverse. Party attention focus.

In addition, Linux is an operating system based on the network environment and has complete network functions. Users can connect to the Internet as a single machine under Linux, and can also set up a local area network (LAN); Linux can also set up various servers to provide Mail, FTP, Web ... various services on the Internet and Intranet. In this trend, Linux has become the operating system that DVR manufacturers are eager to try. Some vendors even say that Linux is more suitable for DVR than Windows.

In fact, it is too early to conclude that "Linux as a DVR operating system will be better than Windows". According to other manufacturers, Linux still has some compatibility issues, such as printer support and Internet connectivity, which are not as good as Windows. In addition, for users who are accustomed to using Windows applications, they may not be comfortable with the way of operating Linux at first; while Linux can read Windows files, but Linux still has the disadvantage of not being able to read files by Windows. Linux is a rising operating system, so when the maintenance staff is not very sufficient, many manufacturers will have certain psychological obstacles when choosing to use Linux systems.

2. Using Windows as the operating interface

For the DVR with PC as its main architecture, the Windows platform tops the list of various operating systems for its simple use and universal application.

In addition, Windows is better than other operating systems in software upgrades. Since the IT industry is closely related to the security industry, as digital technology advances thousands of miles in the IT industry, the development of related technologies is bound to affect the security industry. Windows is loved by many manufacturers because it is highly scalable. Manufacturers believe that because DVR systems cannot stay at a fixed level for a long time, upgradeability is bound to become a key point in system development. If you consider the cost of eliminating the old, once users have higher requirements for the existing system or the original system exposes some defects, most users are unlikely to buy a brand new system to replace, so despite the supplier It is believed that the stability of the system depends on the actual operation of the user. However, the instability of the Windows operating system itself still makes users question. Some manufacturers have said that if only the monitoring system is used, the Windows 98 system is quite stable; but if other programs are run on the Windows platform at the same time, the system is unstable and even crashes are unavoidable.

3. Using RTOS as the operating interface

For single-model or non-PC-based DVRs, RTOS (Real Time Operation System) is the best operating system. This type of vendors on the market is mainly Korea and Japan. Many Korean manufacturers such as 3R, Korea Computer Technologies, Kodicom, Artinix, etc. believe that single-model DVRs have high economic benefits, high stability, and high compatibility with existing security controllers, so they have been one after another for a while. Launched a standalone DVR. For Japanese manufacturers, the commitment to the development of single-type DVRs is mainly based on the consideration of image sharpness, and most PC-based DVRs have lower image quality than single-type DVRs.

However, the biggest challenge for stand-alone DVRs is networking capabilities. Today, with the popularity of networked work, more and more users are using the network. Jonathan Kim of Digital Logic in South Korea said: "When we talk about stand-alone DVRs, the networked remote control part is often missing. But DVRs If the system cannot connect to the network, frankly, it cannot be called a DVR system. " Some Western manufacturers have the same view. For example, the United States, Germany, the United Kingdom, and other Nordic countries have regarded network functions as the key to digital CCTV products. Mike Fawcett, Executive General Manager of Dedicated Micros in the UK, exemplified: "In the United Kingdom, chemical and pharmaceutical plants in the United Kingdom use network-enabled DVR equipment. In addition to saving a lot of manpower costs, they can also monitor the status of staff and production lines from anywhere, so saving A lot of costs. " The networkable feature allows users to remotely monitor via LAN / WAN, Internet and other networks. This feature has been predicted to become the mainstream of the CCTV market in the future. In order to provide products with networking capabilities, single-model DVR manufacturers have fallen into a "price vs. feature" dilemma.