Technical development of high-definition digital movement

The HD movement is mainly composed of lens, image sensor (CCD or CMOS device), ARM/DSP, etc. The lens gathers the light reflected by the subject to the image sensor, and then the image sensor is photoelectrically converted into a digital video signal and output to the chip. After the chip performs a series of digital image signal processing (ISP) and data compression, it is transmitted to the back end through the network Decode the display device, and then realize the functions of video preview, recording, playback and so on. Through the docking of the movement and the dome pan/tilt, various controls of the pan/tilt can also be realized, such as up and down, left and right rotation, zoom, focus, preset points, cruise and more and more rich functions. The core functional modules included in the HD camera movement include image acquisition, image processing, video encoding and decoding, and so on. The image sensor that realizes the image acquisition function mainly includes low illumination, wide dynamic, BSI and other technologies; image processing (ISP) technology includes 3A (automatic exposure, automatic white balance, automatic focus), edge enhancement, 3D noise reduction, image scaling, Flip, brightness, chroma, saturation, contrast adjustment, as well as digital wide dynamic, digital zoom, electronic anti-shake, etc.; image coding and decoding technologies mainly include MPEG4, H.264, MJPEG, multi-stream processing and so on. We know that the high-definition movement has a lot in common with the development technology of digital cameras and DV. With the popularization of digital cameras and DV applications, these technologies have become very mature. At the same time, the security industry has its own characteristics. For example, it is impossible to keep flashing the flash when the light is low, and a large number of videos cannot be directly saved on the camera. A large number of cameras are distributed in various corners of different scenes instead of being taken by users. Wait in the hand. This requires the image sensor of the high-definition movement to have better performance in low illumination and wide dynamic. As CMOS on the high-definition movement gradually dominates the mainstream, there is still a lot of room for improvement in low illumination, wide dynamic, BSI, etc. . What I have to mention here is that Aptina has launched low-illumination image sensors for security applications. OV has also tried to introduce BSI technology on digital cameras into the security industry. SONY is also gradually paying attention to CMOS and beginning to increase the proportion and intensity of its research and development. . We can also see that as long as there is room for improvement, everyone will not stop, but will try to overcome these problems to seize the commanding heights of the market. To There are several important indicators of high-definition movement that need attention, such as power consumption, low illumination, delay, whether the back-end supporting facilities are abundant, and so on. Power consumption Regardless of whether it is an  movement or a digital movement, heat generation is a problem that has to be considered. If the movement is installed in a closed dome camera, and then a heating infrared light board is installed on the outside of the dome camera, it will heat up. Electronic components have a working temperature range, generally below 70°C. If the working temperature exceeds 70°C, the electronic components may be burned out. For the dome camera, although it is necessary to dissipate heat through the fan and the heat insulation layer, it is also limited. The heat dissipation basically depends on where the heat comes from. Therefore, when choosing a million high-definition camera, you must test the movement of the movement. Heat, look at how power consumption heats up, this is very important. To Low illumination In the security industry monitoring, it is impossible to keep flashing the flash when the light is dark. Therefore, Mega HD does not have low illumination characteristics, and its application is extremely restricted. When the light is dim, it will be black, and no matter how high the pixel is, it will lose its meaning. In addition, if the low illuminance is not good, simply relying on externally increasing the power of the infrared lamp to supplement the light will inevitably cause an increase in heat generation. Long-term operation under excessively high temperature will seriously affect the service life of the camera. To Delay As long as it is a digital camera, there are different degrees of delay. For the same 720P high-definition picture, some cameras have a delay of only 0.11 seconds, while others are as high as 0.4 seconds and 0.7 seconds. At this point, we may be wondering why the same Does the resolution have a different delay? Because digital cameras need to go through three processes, encoding, transmission, and decoding display. If you have your own coding and decoding algorithm development capabilities and core underlying technical capabilities, you can optimize processing as much as possible in terms of image encoding, network transmission, and image decoding efficiency, so that the performance reaches the ideal state and the delay is as short as possible. It is very troublesome to control the dome pan/tilt when the delay is too long. Imagine that the client has issued a rotation or stop command to the pan/tilt, but the image has not started to change or is still changing, and the user experience will be very poor. . The color of the high-definition movement can be more realistic than that of an  camera. In the process of  signal transmission, the bright colors cannot be completely separated, and the brightness signal is doped with the color signal, resulting in variegated spots on the picture, while the high-definition movement does not. Under the  movement PAL system, 625 scanning lines, 575 lines after de-blanking, the current upper limit of about 540 lines is already the limit, while the digital high-definition movement can reach more than 800 lines, with a resolution of up to one million or even ten million pixels; HD The movement can combine the video cable, audio cable, and control cable into one, using a network cable instead. It transmits digital signals, and the transmission process is free from electromagnetic interference. The transmission distance can be extended to several kilometers through the optical fiber transceiver. The wiring cost is saved; the image sensor used by the high-definition movement also outputs digital signals, and the processing chip docked with it can directly encode and compress the collected data without relying on external -to-digital conversion and encoding compression chips. Greatly increase and greatly reduce the cost; There are two types of applications for g high wire movement, one is to use coaxial cable for transmission, and the other is to use network cable for transmission. The latter needs to add a separate processing chip to realize aog-to-digital signal conversion, and to perform video encoding and compression, which involves the docking of hardware and the docking of software data transmission protocols, which will greatly increase the cost of the product. The use of coaxial cable transmission can inherit the wiring of the original og system, and the system composition and device management methods remain unchanged. If the original camera does not have a high line count, a new back-end video storage device needs to be replaced; the preview is not compressed The video is very clear, and the playback video will be lost due to compression processing; the coaxial cable is used to transmit the ag video signal, which is not suitable for the environment with electromagnetic interference; the transmission distance is very limited, and generally does not exceed 100 metres. The HD-SDI high-definition core is very similar to the g high-line. The wiring of the original aog system can also be used, but there will be higher requirements for the back-end video storage device. If encoding and compression is not performed, it will consume hard disk space. It will be very amazing. If you want to encode and compress multiple channels of high-definition pictures at the same time, the processing power of the CPU will be very high; if you are playing back the encoded and compressed video, the image quality will also have obvious loss; Whether it is an anmovement or a digital movement, what is finally presented to customers is a comprehensive monitoring application management platform that can realize the functions of previewing the picture, recalling the video, putting it on the TV wall, and alarming. For ordinary users, simple operation of the platform interface and high integration are the main requirements. Therefore, whether the back-end applications of the high-definition movement are abundant is also a very important factor. At present, there is no unified standard for various manufacturers of high-definition cameras, and ONVIF needs a process to realize seamless connection of various devices. At present, we mainly rely on competent engineering companies and manufacturers to promote the docking of various equipment and integrate resources of various heterogeneous systems. Under this circumstance, the more various applications of high-definition core manufacturers in the market, the more corresponding platform software that can be connected to the high-definition core, whether the high-definition core supports the ONVIF protocol and continues to update, It also determines whether this movement can seamlessly connect with more back-end devices in the future. With the development of millions of high-definition network cameras, the camera chip realizes more functions, while the integration is getting higher and higher. As a result, there will be fewer and fewer peripheral components, and the power consumption will be lower and lower. The high-definition digital core There will be more and more applications. In addition to realizing the functions of the traditional smart ball, the high-definition digital movement itself, as a digital product, will integrate more intelligent functions in the future, such as people counting, trigger area, intelligent motion detection, camera tampering detection and other functions.