What exactly is high-definition in the true sense? What standard does the high-definition surveillance camera as a front-end device for high-definition surveillance have?
About the definition of "HD"
Let us first look at the definition of high definition by digital TV technology. Digital TV is mainly divided into standard definition TV and high definition TV. Standard definition television (SDTV) refers to a digital television system with an image quality equivalent to that of conventional analog color television systems, such as PAL, with a resolution of approximately 500 TV lines and a bit rate of approximately 5 Mbps; high definition television (HDTV) It refers to the digital resolution of the horizontal and vertical resolutions that are about twice that of the current analog color TV system, the aspect ratio of 16: 9, the resolution is about 800 TV lines or more, and the code rate is about 20Mbps.
In ITU-R BT.1201, ITU proposed several standards for ultra-high definition images (HRI). The basic element is that the minimum resolution of the image is 1920x1080, and HRI is divided into four levels, including HRI0, HRI1, The resolutions of HRI2 and HRI3 are 1920x1080, 3840x2160, 5760x3240, and 7580x4320, respectively.
According to the above definition, corresponding to video surveillance, the analog-to-digital hybrid surveillance with analog cameras can reach the highest standard definition. If digitized, the highest resolution can reach 4CIF or D1 resolution, about 400,000 pixels, the resolution is Between 300 ~ 500 lines; adopt the IP surveillance of high-definition network camera, if you want to achieve the resolution of 800 TV lines, then the resolution of the network camera must reach at least the standard of 1280x720, about 900,000 pixels, which is two of the mixed analog and digital monitoring Multiple times; if you use a 2 million pixel network camera, you will meet the requirements of ultra-high-definition images. The 16: 9 aspect ratio of the network camera corresponds to a resolution of 1920x1080, and the 4: 3 aspect ratio of the network camera corresponds to The resolution is 1600x1200.
HD does not equal megapixels
In the field of video surveillance, especially in the field of network video surveillance, a technical term often heard is called "megapixel", which specifically refers to the number of image sensor elements of the camera, that is, resolution. Since high resolution is often accompanied by a large amount of image data, this often affects the frame rate. Therefore, megapixel cameras often emphasize the resolution of the image, and the frame rate of the image often fails to meet the real-time requirements (25 / 30fps).
In fact, high resolution is a necessary condition for "high definition", but it is not a sufficient condition. High resolution can only be said to be similar to static "high definition". So, in addition to high resolution, what are the aspects of true "high-definition" picture quality?
The HDTV standard not only defines the requirements for resolution (720P, 1080i / P), but also defines the requirements for full frame rate (25 / 30fps) and the requirements for color fidelity. At the same time, HDTV defines a 16: 9 widescreen format.
Frame size refers to the product of the number of horizontal pixels and the number of vertical pixels, such as 1 2 8 0 x 7 2 0 or 1 9 2 0 x 1 0 8 0. Frame rate is defined as the number of image frames per second (fps). The high-definition camera adopts progressive scanning, and each frame of the image is sequentially scanned by the electron beam sequentially line by line. The analog camera uses interlaced scanning. The line scanning frequency of interlaced scanning is half of that of progressive scanning. Interlaced scanning will bring many shortcomings, such as inter-row flicker effect, parallel phenomenon and vertical edge jagged phenomenon. Effect. Interlaced scanning will reduce the clarity of the moving picture.
Since the luminance signal and the chrominance signal in the analog video signal occupy the same frequency band, when comb filtering (bright color separation) is performed by the video acquisition chip, it is difficult to completely separate the chrominance and the luminance signal, resulting in noise spots With the color penetration phenomenon, the HD camera does not have this trouble, the color is more realistic, more layered, and the picture saturation is better.
From analog to network HD
Video surveillance has experienced three stages of development: analog, digital, and network. Prior to 2000, video surveillance was basically based on a pure analog system. The network mode of the system was analog camera + matrix + analog video recorder.
Since 2000, with the maturity of digital video codec and multimedia processing chip technology, digital monitoring systems with video compression cards and embedded hard disk recorders as core products have gradually replaced analog monitoring systems and become the mainstream of the market. The transformation of monitoring from analog to digital focuses on solving the core problems of two aspects of video monitoring in the pure analog era: transmission and storage.
With the continuous improvement of network infrastructure, the continuous improvement of network bandwidth and video compression algorithms, video codecs and network cameras have become mainstream network products, and network-based video surveillance systems have begun to be widely promoted in the market and many industries. And application, network monitoring is becoming a new development trend of video surveillance with its convenient and flexible networking mode and application advantages.
The current high-definition front-end products include two types: one is a high-definition megapixel digital camera, and the other is a high-definition megapixel network camera. Because the high-definition digital camera currently lacks the back-end supporting high-definition encoder and high-definition hard disk recorder, and the overall cost and engineering application complexity are much higher than the high-definition network camera. Therefore, the current high-definition surveillance system is basically based on the application of high-definition network cameras, and the market is mainly based on 720p and 1080p products. The effective resolution of 720p is 1280 x 720, and the effective pixels reach 1 million, which is equivalent to 2.5 times the standard definition D1. The effective pixels of 1080p are 1920 x 1080, and the effective pixels reach 2 million, which is equivalent to 5 times of standard definition D1.
Because network cameras are highly integrated, easy to use, and easy to maintain, future high-definition surveillance front-ends will be based on high-definition network camera products.
Iso Room,Iso 8 Clean Room,Clean Room Standard,Clean Room Operating Costs
Dongguan V1 Environmental Technology Co., Ltd. , https://www.v1airpurifier.com