The difference between different HD video surveillance technologies

What is the difference between HD video surveillance technology and ordinary definition video surveillance? How to distinguish high-definition and understand the difference between different high-definition video surveillance technologies? This article is to help users of high-definition video surveillance technology understand the application status of the technology.

Before understanding HD video surveillance technology, the first thing that needs to be clarified is the concept of HD. In today's video surveillance field of the security industry or TV, movies and other multimedia applications, "HD" is the key performance of merchants, and it is also an important indicator for consumers to measure product performance. It is also because HD is a hot word and an important keyword to attract consumers' attention. HD is often reduced to the "concept" of promotion, and it is out of touch with the original basic definition.

When high-definition television first appeared, Japan, Europe, and the United States had three sets of high-definition technology solutions competing with each other. Among them, Japan and Europe used analog high-definition, while the overall performance of DigiCipher, the all-digital high-definition solution of General Motors of the United States, exceeded the previous two. And become the mainstream standard technology of high definition. Therefore, most of the high-definition technology solutions used today are digital technologies. The definition of high-definition originally originated from the broadcast television industry and is called "HDTV". In the 1990s, the high-definition television standard format determined by the American Society of Motion Picture and Television Engineers (SMPTE) included three standard formats, 1080i, 720P, and 1080P. Therefore, among the three standard formats 1080i, 720P and 1080P, 720p has been defined as high-definition television (HDTV) by many American TV stations. But this is only the case before the International Telecommunication Union Radiocommunication Group (ITU-R) did not define high definition.

According to the definition given by the International Telecommunication Union Radiocommunication Group (ITU-R): "High-definition television should be a transparent system, a viewer with normal vision can see the image at three times the height of the display screen of the system The quality should have the impression obtained when viewing the original scene or performance ". In order to achieve this viewing effect, through a large number of experimental comparisons, people have reached a consistent conclusion: the original number of pixels of the image displayed on the HDTV TV screen should not be less than 2 million pixels. This is also the basic requirement for high-definition television specified by ITU-R, that is, the image resolution should reach 1920 × 1080 pixels. It should be noted that the definition expressed by the number of pixels and the definition expressed by the TV line are approximately proportional to the display effect, but they are conceptually different.

The industry standard GY / T155-2000 of the State Administration of Radio, Film and Television is stipulated in the "Video Parameter Values ​​for the Production and Exchange of High-Definition Television Programs": High-definition digital television 25 frames per second interlaced scanning or 24 frames progressive Scanning, 1125 lines per frame, the number of effective scanning lines per frame is 1080, and the number of effective samples per line is 1920, which is 1920 × 1080 (1080i). As for the difference between 1080i and 1080P, this involves the difference between progressive scanning and interlaced scanning. Because of the improvement of display technology, interlaced scanning signals can be converted into progressive scanning signals because of the appearance of double-line technology. There is no big difference, of course, in theory, the progressive 1080P is still better than 1080i.

With the advancement of technology, 5 million and 8 million (also known as 4K) pixel devices have appeared in the field of radio, television, and security monitoring, so 1080P with 2 million pixels can be regarded as the minimum standard for high definition.

Because there is no corresponding industry standard, the current video surveillance industry still uses the definition of high definition in the broadcast and television industry, that is, the high-definition concept defined by the International Telecommunication Union (ITU-R). But because of the interference of the 720P "high definition" concept defined by SMPTE in the United States, even cameras or video surveillance devices that approach 720P resolution are called high definition by some people. This is because SMPTE has certain authority. In the past, the definition of high definition included 72OP, so 1080P is also called Full HD (FHD: FullHD).

However, from a strict technical definition, the definition of 720P cannot reach high definition. Of course, the definition is higher than standard definition (SD), so it is more accurate to call it "quasi-high definition".

The value of HD network video surveillance technology

The biggest advantage of high-definition network video surveillance is in the three links of IP-based data transmission, storage and processing, and in the two links of image acquisition and display, because the camera and the display screen use analog signals to restore and collect images of. High-definition network video surveillance requires high-speed transmission, large-capacity storage, and intelligent processing, which is also the development direction of surveillance technology.

Obstacles to the popularization of HD network video surveillance technology

The author is most concerned about the practical application of the high-definition network video surveillance system, especially in civilian use. It is the problem of network transmission costs. At present, the transmission speed of the domestic Internet is still a constraint on the transmission of high-definition images in real time.

In today's big data era, storage is under tremendous pressure, but storage can be improved through superimposed investment, and storage is faster than transmission. Compared with the high-definition network transmission, it particularly involves the improvement of the access network, which is difficult to transmit. Once the access network is upgraded, the pressure on the dry network is doubled. Therefore, the transmission technology is a technical difficulty in 3-5 years.

A high-definition camera requires at least 2M of bandwidth to access the Internet, and even if you purchase Internet services in bulk, the annual network fee for each high-definition camera will not be less than 800 yuan (Beijing area). The cost of network services is a huge expense in large-scale security projects.

Of course, if high-definition video surveillance is not available on the WAN, network fees will not be a problem, but this is contrary to the original meaning of online video surveillance. Or you can use a certain compression technology to reduce the code stream, but in fact, high-definition high-definition pictures correspond to high-speed transmission. There are some shortcuts for the high-speed transmission required for high-definition pictures, such as intelligent compression and the identification of effective information to improve the effective compression of information. But the bottom line of compression is not distortion, otherwise HD will lose its meaning.

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