Security monitoring how to get high-definition video image information

March 26, 2019

When it comes to high-definition surveillance, high-quality images are the premise of high-definition, and are also a prerequisite for the development of video surveillance. If you can see a person's facial features in a crowded subway station, whether a vehicle license plate that can be quickly driven on a highway can be identified, etc., clear images are required. To see more clearly, you must rely on the image quality that the front-end camera can provide. The disadvantages of standard definition cameras are blurry images and low resolution. When sudden events need to be reviewed for video playback, the details of the event site are difficult to discern and cannot provide effective information. In contrast, high-definition cameras can bring higher pixels, wider monitoring range, higher resolution, and quickly improve the quality of traditional video surveillance.

Of course, high-definition monitoring is a unified whole, involving multiple aspects of the monitoring system, including front-end video capture, intermediate video transmission, back-end HD storage, display, analysis, and linkage. Due to space limitations, this article only discusses how to ensure the collection of high-definition information on the front-end part.

CMOS is more suitable for HD era

As the core component of the camera, the sensor determines the image quality. The image of the subject is focused on the sensor chip via the lens, and the sensor processes it according to the intensity of the light to form a video signal output. CCD and CMOS are two kinds of image sensors that are commonly used at present, both use photodiode for photoelectric conversion and convert the image into digital data, and the main difference is that the digital data is transmitted in different ways. Divided by performance, they are basically reflected in the sensitivity, noise processing and power consumption. In the comparison of sensors of the same size, the resolution of CCD is generally much higher than that of CMOS. Therefore, we usually use the CCD technology as our own sensing device in the low-lightness SD cameras that are common in the market. In the SD era, CCD is undoubtedly more popular than CMOS.

The CCD manufacturing process is complicated, and it is only in the hands of a small number of manufacturers. As a result, the manufacturing cost remains high. Every increase in the size of the CCD results in a geometric increase in the cost. Therefore, if the monitoring is to go in high definition, the CCD clearly has a limited development prospect. The most important feature of CMOS is its low cost and low power consumption. In the case of the same number of pixels, the price is lower and the price/performance ratio can be continuously developed toward higher pixels and higher resolution. The high-definition monitoring is very sensitive to the cost, and therefore, most HD cameras in the market use it. CMOS.

To achieve high-definition, it is necessary to cooperate in many aspects such as wide dynamics, automatic white balance, sharpness of images, and digital noise reduction, color adjustment, and light compensation. Only when these comprehensive performances can be well represented and they can coordinate with each other can they be said to be the true realization of high-definition. The combination of CMOS and other image processing technologies far exceeds that of CCDs, with a higher dynamic range and faster response speed, which is more suitable for the large data volume characteristics of high-definition monitoring. In addition, with the development of technology, the sensitivity of CMOS has also been greatly improved. In effect, some CMOS sensors are now comparable to CCDs.

HD cameras need to have an HD lens
Security's high-definition surveillance not only poses a high-definition demand for cameras but also professional lenses. HD lenses are of great importance for HD surveillance. The definition of the camera in the HD era can reach a million levels, but if the camera with which it is matched does not match the camera's super resolution.

In the same camera situation, the final performance of the picture, the resolution of the lens played a decisive role. HD lenses outperform ordinary lenses in three main ways: clarity, spectral transmission, and spectral correction. High-definition lens can enhance the contrast and brightness of the picture, obtain high-definition image effects, and provide richer details for the picture.

So how do you choose HD lens? In general, when selecting a lens, a lens product that is the same or higher than its pixel size is selected according to the highest resolution of the camera. In addition, we must analyze the specific characteristics of the project. For example, in a place where night shooting is required, in order for a day/night camera to have a better shooting effect, it is necessary to rely on an HD lens having a larger aperture, such as 2/3 inch, and a better aperture value F so that the camera can acquire More luminous flux, to help the camera get better shooting at night. Some projects need to use IR fill light when using the camera, so you should use the lens with IR function, so you can get a brighter picture at night and reduce the problem of night focus. For more demanding environments, such as with a laser light, monitoring of long-range targets must ensure that non-visible light wavelengths can still achieve transmission rates of more than 60% at 900um.

The role of video processor can not be ignored

To achieve a clear image quality, in addition to the front lens, the sensor part of the light processing, image processing part is also a camera can not be ignored. The images obtained directly from the sensors often have poor results. There is a large gap between the colors and the details and the actual images, which is difficult to use as evidence afterwards. After image processing, including face detection, noise filtering, elimination of dead pixels, skin color correction, automatic white balance, auto exposure, and edge enhancement, the image can be made more detailed and closer to the real world image. Therefore what kind of processor is used will directly affect the monitoring effect.

Currently, many high-definition cameras directly use ISPs provided by CMOS manufacturers or integrated CMOS (built-in ISP image processors). These ISP image processors can cope with general scenes, but they have poor processing performance for scenes requiring wide dynamics. The monitoring system is different from the consumer electronics or broadcasting application mode. In the video monitoring system, the monitored object cannot match the camera angle, so in the case of backlight, backlight, etc., the ordinary ISP image processor cannot provide effective wide dynamic image , resulting in a drop in the visible image quality.

In the era of high-definition, processors not only carry a lot of work such as image processing and analysis, codec compression, but also embed a large number of intelligent analysis algorithms to analyze massive high-definition data and bear more important roles. For example, the TMS320DM368 video processor used in the Andertek camcorder series of Tyco Integrated Security has a powerful and comprehensive function. In addition to supporting higher video resolution, customers can also get more than 40% of ARM performance enhancements for high definition. Video processing and advanced user experience provide advanced application programming interfaces (APIs). The DM368 also supports multi-format high-definition video, including VC1, MPEG2, MPEG4, MJPEG, and H.264, and supports up to 30 frames per second of the 1080p standard.

In addition, the device not only supports multi-format decoding, multi-rate multi-streaming, and high-definition multi-channel functions, but also provides audio, voice, and other high-definition video codecs, enabling greater flexibility and lower design complexity. Because the DM368 is pin-to-pin and software compatible, the TITMS320DM365 DaVinci video processor can be used to support a full lineup of 1080p products from D1, 720p and up to 30 frames per second, enabling customers to build scalable products Line, supports a variety of codecs. ISP software implementation provides features such as video stabilization, face detection, noise filtering, auto white balance, auto exposure, and edge enhancement.

Image compression is key

In view of the current state of development of storage devices, in the case that large-capacity hard disks are still expensive, original images must be compressed in order to reduce storage and broadband costs. Although the higher the compression rate, the more blurred the image, but if the recording capacity per hour reaches several G, the customer is unacceptable. Under the same conditions of the chip, the algorithm plays a key role. In order to achieve an equilibrium, good manufacturers use the H.264 algorithm. H.264 can achieve broadcast-quality HD video resolutions of 720p and 1080p at lower bandwidths. At the same image quality level, a 115-second video stream compares bit rates under different video standards. In the absence of motion compensation, the H.264 encoder is at least three times more efficient than the MPEG-4 encoder and six times more efficient than the M-JPEG encoder.

With the same image quality, the video surveillance system supporting the H.264 compression standard can reduce the storage cost and bandwidth consumption by at least 50% compared with the traditional compression technology. With the ever-increasing scale of the system and the increasing demand for high-resolution images and high frame rates, this highly efficient compression technology will likely drive megapixel cameras at the highest speeds for applications that require high resolution and high frame rates. Speed ​​monitoring sites such as airports, retail stores, banks, and entertainment venues.

The HD camera series supports the H.264 format, which enables large-scale compression of large files without affecting image quality, resulting in higher frame rates and image resolution, allowing higher-quality images to be output. Tyco HD cameras also provide intelligent image cropping technology, which can avoid some unimportant images on the sensor, and large images can be cropped horizontally and vertically. Allows only transmission and storage of required data. Obsolete data can reduce the use of large amounts of storage space and bandwidth, providing powerful support for overall HD surveillance.

It can be said whether it is possible to win the fierce competition in video surveillance, whether it can keep up with the trend of HD. The choice of high-definition front-end is the first step, and the front-end quality directly affects the monitoring effect. From the actual use of the effect point of view, with the same back-end monitoring program, fight is the high-definition front-end acquisition information. High-quality images provide a solid foundation for real-time monitoring, screen calling, detail browsing, and intelligent analysis, which greatly enhances the application value of the system.

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