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Image Preprocessing Techniques In Video Surveillance

Improve monitoring of image quality and coded transmission efficiency monitoring system involving multiple links, upstream from the actual scene, to the middle of the transmission network, to the user terminal downstream, including image acquisition, compression, transmission or storage, decompression and display section, any one of the upstream part of the problem, the impact on the image quality is not able to correct or remedy the downstream part of. Part of the video signal preprocessing at the most upstream monitoring systems, for the purposes of the main processing, video surveillance, the main processing generally refers to video compression coding and transmission, previously known as the pretreatment process in general, often it will merge the video capture part. Undoubtedly, video capture preprocessing is an important part of the pretreatment effect will directly affect the quality and efficiency of the subsequent image acquisition coded transmission process. There is a phenomenon can be effectively described in terms of the role of pre-processing of image quality improvement is: for the same scene, the same bit rate, the larger the difference between the quality of ip camera of different manufacturers often a decoded output video. Especially in the relatively harsh environment, the difference is more significant. One important reason for this difference is that: in the monitoring system, although we are using standardized video compression method, but the quality of the final output image decoding depends largely on whether the level of pretreatment, pretreatment is good or bad, sometimes including appropriate follow-up treatment. As people's awareness of the importance of pre-treatment continues to improve, with integrated signal processor chip and the ability to continue to enhance the industry's increasing emphasis on pre-processing of the video signal, high-quality surveillance products on the market must not be separated high-quality video preprocessing methods. The first function is to improve the quality of video pre-encoded video. In the actual video surveillance applications, unlike entertainment video quality can be guaranteed because there are high-quality collection of video cameras, sound studio shooting environment and professional and technical personnel at any human intervention. The video surveillance system due to the impact of cost and environmental factors, acquired the original video quality is not high, even very low. For example, due to the impact on the environment, noise, light, motion, etc., often collected images often appear blurred, distorted, noise, too bright or too dark, color and other effects is not clear. For such a relatively poor video compression and then, transmitted, decoded for display, the user sees the video monitor is often not satisfactory. How to improve the collection of video quality problems in the existing conditions placed on it in front of us. In response, a response that is important part of the video capture preprocessing (preprocessing), to facilitate the capture of video to improve the quality of video in favor of the subsequent processing in order to facilitate the user to extract information of interest in the video. The second function is to improve the pre-processing of video coding efficiency, and to the rate control. We know that, either wired or wireless video transmission, are based on data packet transmission network, the transmission rate of the signal instability, rates vary with the user's level of congestion, physical media channel is constantly changing. To change the rate of the channel in such a stable and efficient transmission of the compressed video images, in addition to the rate-dependent control of the encoder can also be used to assist in the pretreatment method of implementation. Before encoding the image preprocessing, the control input to the encoder video data, thereby indirectly controlling the encoder output bit rate, not only through the overflow buffer to control the degree of quantization step, and also added the pre-processing the input video data is controlled. For example, when the channel narrows, we can input video information according to the channel bandwidth, a degree of smoothing to reduce details, or for down-sampling processing, frame skip process, the video encoding bit rate can be matched to the channel bandwidth. Of course, since access to the channel status information is too much trouble, you can use statistics to establish an approximate model of channel bandwidth changes, and then based on this model to determine the method and degree of pretreatment. The video pre-processing is the first in the analog domain, including the video signal band-limited analog filtering, noise reduction, AGC, white balance correction, and r. With digital video capture process technology, these simple pretreatment method has been integrated into the chip are mostly gone. Now, video pre-processing is performed in the digital domain, that is carried out after the digital video capture, give full play to the convenience of the digital signal, efficient, flexible and consistent superiority. Currently, the video surveillance in common pretreatment method in addition to basic image filtering, image de-noising and a variety of image enhancement processing, but also the emergence of a variety of pretreatment methods for specific applications, such as backlight or low light treatment, rain and fog smoke treatment, treatment interval of interest.


Original article published on amazines.com

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