What exactly is a high-definition video conference camera in the end?

What exactly is a high-definition video conference camera in the end?

HD in the field of video surveillance is the hottest topic today. What is the real HD in the end? ITU proposes several standards for ultra-high definition imagery (HRI) in Recommendation ITU-R BT.1201. The basic element is the minimum resolution of the image is 1920x1080, and HRI is divided into four levels, including HRI0, HRI1, and HRI1. HRI2 and HRI3, with resolutions of 1920x1080, 3840x2160, 5760x3240, and 7580x4320, respectively. What are the standards of high-definition surveillance cameras as high-definition surveillance front-end devices?

Let's take a look at the definition of high definition in digital television technology. Digital television is mainly divided into standard definition television and high-definition television. 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, a code rate of approximately 5 Mbps, and high definition television (HDTV). Refers to a digital television system with horizontal resolution and vertical resolution that is approximately twice that of current analog color television systems, and a 16:9 aspect ratio, with a resolution of approximately 800 television lines or more, and a code rate of approximately 20 Mbps.

According to the above definition, corresponding to video surveillance, the use of analog cameras for analog-to-digital monitoring can achieve up to standard definition. With digital processing, the highest resolution can reach 4CIF or D1 resolution, about 400,000 pixels, and the resolution is Between 300 and 500 lines; IP surveillance using high-definition network cameras, if you want to achieve the definition of 800 TV lines, then the resolution of the network camera must be at least 1280x720 standard, about 900,000 pixels, is the two modular monitoring Multiple times; if a 2-megapixel network camera is used, the requirements for ultra-high definition images are met. The network camera with a 16:9 aspect ratio corresponds to a network camera with a resolution of 1920x1080 and an aspect ratio of 4:3. The resolution is 1600x1200.

In the field of video surveillance, especially in the field of network video surveillance, a frequently-received technical term is “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 tend to emphasize the resolution of the image, but often do not meet the real-time requirements (25/30fps) in the image frame rate.

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". Then, in addition to the high resolution, what is the real "high definition" picture? The HDTV standard not only defines the resolution requirements (720P, 1080i/P), but also defines the full frame rate requirement (25/30 fps) and color fidelity requirements. At the same time, HDTV defines a 16:9 widescreen format. The 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 . The frame rate is defined as the number of image frames per second (fps). High-definition video cameras use progressive scan, and each frame of the image is scanned sequentially from one line to one line of electron beams. The analog camera uses interlaced scanning, and the interlaced scanning frequency is half that of progressive scanning. Interlaced scanning brings many disadvantages, such as inter-line flicker effects, parallelism, and vertical edge aliasing. Effect. Interlacing results in reduced definition of the moving picture.

Since the luminance signal and the chrominance signal in the analog video signal occupy the same frequency band and are comb-filtered (bright-color separation) by the video acquisition chip, it is difficult to completely separate the chrominance from the luminance signal, resulting in variegated spots on the screen. With the phenomenon of color penetration, HD camcorders do not have such annoyance. The colors are more realistic, more layered, and the picture saturation is better.

The current high-definition front-end products include two types: one is an HD megapixel digital camera, and the other is an HD megapixel network camera. Due to the lack of high-end digital cameras and high-definition hard disk recorders, the overall cost and engineering application complexity is much higher than that of high-definition network cameras. Therefore, the current high-definition surveillance system is basically based on the application of high-definition network cameras, the market mainly to 720p and 1080p products. The effective resolution of 720p is 1280 x 720 and the effective pixel is 1 million, which is equivalent to 2.5 times that of SD D1. The effective pixel of 1080p is 1920 x 1080, and the effective pixel is up to 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, the future high-definition monitoring front-end will be based on high-definition network camera products.