With the continuous development of society, rapid economic development and rapid advancements in technology, public order security, production safety, and property safety have received more and more attention from people, so that video surveillance featuring video information has become more widely used in various industries. The field, from the traditional security monitoring to management and production management monitoring development, from indoor to unattended monitoring of specific applications.
The traditional monitoring model can no longer meet the security needs of the government's “Safe Cityâ€, financial system, higher education, supervision, prisons, and Wenbo, and the network video monitoring system featuring network, intelligence, digitization, and remoteness is Become a new application trend and form an efficient, safe, advanced network video surveillance system.
In the network video surveillance system, H. 264 coding compression algorithm has been successfully promoted, with the gradual recognition of users, the reduction of the price and the improvement of the function, it will inevitably usher in the era of high-definition network cameras to dominate the field of future video surveillance.
The first part of the development history of high-definition network camera, a description of high-definition megapixel network camera:
In this "HD" era, everywhere you can see products with HD "title", what is HD in the end? What is a megapixel network camera?
1, HD definition:
At present, the definition of high-definition only appears in the broadcasting industry. According to relevant standards, the general display ratio is 16:9, and at least the digital signals with 1080i (resolution of 1920×1080) can be resolved, or the number of scanning lines must be reached in both vertical and horizontal directions. The 720P digital signal can only be classified as a high-definition product if it meets or exceeds the above criteria.
2. Definition of HD megapixel network camera:
The HD megapixel network camera is a network camera capable of continuously acquiring a maximum resolution of more than 720P (1280*720) or more than a Full HD (1080P, resolution of 1920*1080) to a higher 2048×1536 picture at more than 12 FPS. Satisfying the high-definition index mentioned in the HD definition above, the vertical and horizontal directions of the scan lines all meet the requirements of the 720P digital signal, which can be understood as the megapixel level in HD products.
3, HD network camera operating characteristics:
High-definition network cameras are the source of high-quality imaging and monitoring systems. Digital acquisition is performed directly on the video (actual high-end digital sensors (CCD\CMOS), and most of them are on the market today.) High-definition encoding compression and IP encapsulation (that is, through The network module compresses analog signals into digital signals, and then uses IP networks to carry high-definition video streams to achieve real-time HD monitoring, recording, playback, and forwarding; its video chips are megapixel CCD and COMS sensors (currently The CCD sensor pixels of mainstream cameras are mostly 440,000 pixels, and more video information can be obtained. The monitor picture is clearer and natural.
Second, the advantages of HD megapixel network camera:
General megapixel network cameras have the following advantages over traditional analog cameras and ordinary network cameras:
1, high-definition, the use of megapixel sensor can obtain more video information, generally up to 1280 × 720, 1920 × 1080, 1280 × 1024, 1392 × 1024, 1628 × 1236 or even 2048 × 1536 resolution . (In the field of surveillance, the first two resolutions are mainly based on video surveillance for security surveillance, and the latter are mainly based on road capture. In actual project applications, 1920×1080 is often referred to as 1080P due to system cost and effect requirements. Take a picture of the road.)
2, the image display quality is higher, to better capture details.
3, progressive scan CCD / COMS (high-end digital CMOS with progressive scan, its price is even more expensive than the CCD) to make the screen clearer, natural and smooth; easy integration of intelligent analysis capabilities.
4, can support HDTV widescreen output mode (16:9), HDTV achieved a huge leap in image quality, which means a clearer image, better color fidelity and widescreen format.
NTSC and HDTV have different screen aspect ratios 5 and wider coverage. The same surveillance area can replace the existing multiple fixed-point cameras and an all-around camera, saving cable, installation and maintenance costs.
Third, the development process and trends of high-definition network cameras:
Closed-circuit monitoring systems have grown with the advent of television and video cameras. In the course of a short history of several decades, starting from the 1970s and 1980s, with the rise of the new technology revolution, microprocessors Further popularization and development, from the birth of black-and-white cameras to the introduction of high-definition cameras, the number of camera lines from 380 lines to the current high-definition camera lines can reach thousands of lines.
In the field of video surveillance, it has also evolved into the current stage of high-definition network cameras, where high-definition video is HDTV (High Definision TV). With the popularization and large-scale use of surveillance systems in the international market and the domestic market, people are demanding more and more images. From the very beginning, they can see images, and now they want clear images, and they can perform processing analysis in the future. High-definition image. Therefore, with the continuous development of the high-definition industry and the demand of users for high-definition video, Full HD has become a new trend in the development of the high-definition industry.
The second part of the type of HD network camera, the importance of the sensor (Sensor):
The camera sensor is divided into CCD and CMOS. The sharpness of the camera depends on the performance of the Sensor. Compared with the CMOS sensor, the CCD sensor is superior to COMS in terms of sensitivity, noise control, high-quality image output, and dynamic image performance.
The most important feature of CMOS cameras is that they can be integrated on the same chip of the image sensor as a single-chip camera that integrates all the camera's functional circuits. Compared with CCD cameras, CMOS cameras have the advantages of high integration, small size, low power consumption, high frame rate, fast read speed, simple manufacturing process, and low price. However, the CMOS camera has a fixed pattern of noise that affects the image quality. In the same size, the sensitivity of the CMOS camera is not as good as the shortcoming of the CCD camera.
Second, HD megapixel network camera transmission, encoding compression method:
1. Today, HD megapixel network camera generally has two kinds of signal transmission: one is Mono/RAW transmission, and it is directly converted to a digital signal through an A/D converter chip. No compression encoding is performed on the network and the data is directly transmitted. It is transmitted to the computer and displayed on the computer by means of computer processing; the other is code transmission.
2, the current network camera encoding compression methods are:
(1), JPEG, MJPEG:
1, JPEG compression technology is the basis of all image compression technology, suitable for static image compression, direct processing of the entire picture, the compression ratio is 20-80 times, the resolution has no choice.
2. MJPEG (Motion JPEG) is a dynamic image compression technology developed on the basis of JPEG. It only compresses a certain frame, but basically does not consider the changes between different frames in the video stream. Later, there was a multi-layer JPEG (ML-JPEG) compression technique. Gradient technology was used to transfer low-resolution image files first, and then send more detailed compression data to improve the picture quality.
(2), MPEG-4:
MPEG-4 is mainly used in three areas, digital television, interactive graphics applications (including content synthesis technology), and interactive multimedia. Most megapixel network camera products at home and abroad generally use MJPEG/MPEG-4 video stream encoding and transmission. The advantages of MPEG4 in network video surveillance applications mainly include the following aspects:
1, saving storage space: video and audio fully synchronized 40M - 120M / Road / hour, is the same quality of MPEG1 or MJPEG 1/10; save storage hard drive cost investment and the later hard drive replacement costs.
2. Less occupied network transmission bandwidth: Since the compression ratio is more than ten times that of MPEG1 and MJEPG of the same quality, the bandwidth occupied by network transmission is 1/10 of the same quality of MPEG1 and MJEPG. For example, in the bandwidth of 64K, MPEG1 and MJEPG can only transmit 1/2 frame on average, while MPEG4 can transmit 5--7 frames, which will greatly save the rental fees for transmission lines.
3, error recovery ability: When the network transmission error or packet loss phenomenon, MPEG4 affected little and can quickly recover. If the error reaches 1%, MPEG1 can no longer play, but MPEG4 will only have a slight edge blur; Another example is when the network transmission by the instantaneous packet loss phenomenon, MPEG1 recovery takes at least 10 seconds, while MPEG4 only requires 1 ~ 3 seconds.
4, high image quality: can achieve close to the effect of DVD.
5. Variable bandwidth: The network output rate is adjustable from 56K--384K.
(3), H. 264: Today's mainstream video compression format.
H. 264 is a new generation of video compression format developed by the International Telecommunications Union (iTU-T). H. The most valuable part of 264 is the higher data compression ratio. In the same image quality, H. The data compression ratio of 264 can be 2 to 3 times higher than the MPEG-2 used in current DVD systems and 1.5 to 2 times higher than MPEG-4. Because of this, after H. 264 compressed video data requires less bandwidth and is more economical during network transmission. Currently H. 264 has been adopted by DVD Forum and Blu-ray Disc Association, becoming the standard for the new generation of HD DVD, but H. The 264 decoding algorithm is more complex and the computational requirements are even higher than WMA-HD.
The third part of the HD network camera selection considerations First, security surveillance camera selection:
In the video surveillance system, the lens selection of a megapixel HD network camera is also very important. There are various types of security surveillance cameras, and the specifications are also dazzling. It is very important to select a suitable lens in the surveillance project. In the selection of high-definition webcam lenses, the following manual and automatic two aperture lenses are recommended:
1, manual iris lens:
Specifications: Computar lens, M1214-MP, 2/3 "C mount, 12mm/F1.4.
2, automatic iris lens:
Specifications: Fujinon Fujinon, DV3.4X3.8SA-SA1L, 1/2†C mount, 3.8 to 13mm/F1.4, YV4.3X2.8SA-SA2L, 1/3†CS mount, 2.8 to 12mm/F1. 4.
Second, when buying the lens attention to factors:
1, to prevent fakes when buying.
2, to match with the camera, especially the flux F value matching, so that the camera can achieve the desired sensitivity.
3, megapixel camera generally have to buy matching corresponding megapixel lens.
4, look at the appearance of the material, whether with the CMOS / CCD specifications and interface matching to see whether the coating is good, look at the lens type (spherical / aspherical).
5, the application of environmental considerations, the lens type involves the selection of wide-angle lens, standard lens, telephoto lens, zoom lens, fixed-focus lens.
6, personally test the lens quality.
Third, high-definition megapixel network camera purchase points:
From the perspective of high-definition megapixel network cameras introduced in the current domestic market, the compression methods used are mainly MJPEG/MPEG4 and H. 264 is dominant, but there is no clearer quantitative data in terms of its bandwidth and transmission rate. Although the user knows its super high image quality, it still needs the image continuity and transmission under such a high image quality. The bandwidth is doubtful. Therefore, these products need to pay attention to the following points when choosing:
1. Accurately understand the quantitative indicators such as actual bandwidth and transmission rate under high-quality images, and conduct scientific assessment of the project's network resources.
2, using CCD or COMS sensor chip? If the CCD chip scheme, what kind of (single-channel/multi-channel) "output balance" technology is used, does the frame rate meet the actual demand.
3, the cooperation of the optical lens must be matched with the use of industrial-grade million lens or can not reflect the high-definition picture quality advantages of the camera.
4, fully examine the actual performance of such products in low light conditions, in particular, what technology manufacturers use to compensate for low-light imaging.
5, to examine the software features of such products.
The fourth part of the application of high-definition network cameras from the user point of view, urban security monitoring, transportation, airports, financial and other industries users, they have an urgent need for high-definition video images, and the cost of users for the construction of investment is a psychological preparation, the user What concerns is not the financial issue, but whether the HD system provided by the manufacturer can meet the user's expectations.
First, the development of new network technologies provides bandwidth guarantee for megapixel HD transmission:
Safe cities, financial network monitoring and other projects use self-built optical network or local area network to achieve 1000M bandwidth network. This Gigabit bandwidth resource is installed in the front-end of the above-mentioned 200 720P megapixel full-real-time HD cameras (occupying 3Mbps per channel), occupying 60%-80% of the total bandwidth resources (200 channels of 720P may not appear in actual projects. At the same time decoding on the wall, involving the cost of decoding on the wall, more than 50% to 100% of the points in the CIF format decoding on the wall or 1/5 to 1/3 points to decode the wall), so Gigabit network is fully effective support . In the application of high-definition network projects, many megapixel HD cameras are installed at key area monitoring points, and other monitoring points are based on the standard H. 264 compression algorithm Full D1 SD network camera or traditional analog + encoder mode access. Such as bank vaults, important traffic intersections and bays or gates, accidents or frequent occurrence of cases can be equipped with megapixel HD cameras, so that key events, on-site situations in key locations have HD images can be adjusted. The adoption of a megapixel high-definition and standard definition hybrid networking method not only saves equipment costs, but also effectively saves network bandwidth resources. Both the practicality and economy of the system can be perfectly combined to fully satisfy the cost-effectiveness requirements of users. (Note: The actual stable bandwidth of a Gigabit fiber is about 400M. If it is too high, such as 500M, 600M will easily lead to network failure. The actual bandwidth of the above-mentioned 200-channel 720P to the back-end core switch can reach 650M-800M. Gigabit network can actually carry 2-10 Gigabits to a core switch and the actual project is not likely to have a 200 Gb 720P with only one Gigabit fiber, and it is impossible for engineers and engineers to design such a transmission. If the above 200 channels are converted to 1080P and the video bandwidth is calculated by 5M or even a high standard of 6M each, the bandwidth design of the entire transmission network almost needs to be doubled, and the cost is almost doubled, which is why the market is now 1080P can be called loudly, but in the actual project, only the public security monitoring class invested by the government, especially the illegal use of the road, has captured the biggest reason that the project with profitability is widely used.)
As for public network transmission, megapixel HD network cameras support dual-stream technology, such as supporting 1080P+720P+D1+CIF full-real-time dual stream, so that they can use 720P/1080P HD applications locally, and use D1+CIF for remote users to call remotely. In other words, although the current ADSL wide area network technology can not support large-scale megapixel HD network cameras, it can meet the different needs of local and remote users through dual-stream technology.
Second, the development of mass storage technology makes storage no longer a bottleneck for megapixel HD applications:
As described before, based on the standard H. 264 compression technology, high-definition network camera, all the way 720P HD full real-time image stream is 3Mbps, video storage space required for an hour is about 1.35G or so (if 1080P, video recording is usually calculated according to 5Mbps, one hour requires 2.25G); Often, users often ask: A megapixel camera needs such a large storage space, how many megapixels? In fact, a megapixel HD camera can replace many ordinary cameras. With high-resolution image quality, the storage of videos will become more valuable (policy-based surveillance systems, and 90% of the final results are based on high-definition video playback).
Network storage systems (including storage servers and storage devices) are required for high definition image recording of high definition network cameras. The main connection methods of storage servers and storage devices are DAS direct connection, NAS network hard disk, and SAN (FC SAN and IP SAN) storage area networks. IP SAN uses IP architecture for Ethernet transmission and has good scalability and sharing. And lower application costs for allocation are one of the major technologies currently used for large and medium-sized centralized monitoring and storage. On the other hand, the mainstream data hard disk capacity used in IT has been terabytes or more, and the price of 2TB data hard disks has been popularized (calculated at an hourly data volume of 1.35G, a 1TB (actually available about 920G) data hard disk can store approximately 720P. 680 hours of video images or 1 hour of video recorded by 680 cameras).
Third, the LCD monitor has become the new favorite of high-definition video surveillance:
The high-definition surveillance industry does not have its own standards, so currently the major HD network camera manufacturers are all referring to the HDTV HDTV technology standards. There are two internationally recognized standards for HD: the video vertical resolution is 720p or 1080i; the video aspect ratio is 16:9. In the past few years, driven by the consumer electronics market, coupled with the shift of CRT TVs to liquid crystal and plasma TV screens, HDTV has achieved great success. Currently, the mainstream LCD monitors on the market are 21.5′′ and 24′′ with a resolution of 1920×1080. They can be compatible with point-to-point 720p and 1080p full HD video displays in the 16:9 format. The mainstream size of LCD TVs is 42′′, which is also the standard display size of 1080P HD. These LCD monitors and LCD TVs have high-definition interfaces such as YPbPr and HDMI, which meet the requirements of high-definition network camera video display. Some mainstream manufacturers' panels can reach 5ms or even higher 2ms, which is enough to meet the image refresh requirements of 25fps ~ 30fps.
Fortunately, security HD LCD monitors also followed closely and achieved rapid development. Some LCDs based on DID technology have the advantages of ultra-lightweight, low power consumption, high contrast, no flicker, low cost, etc., and have promoted its application in the field of security monitoring, especially in the video walls of command centers of some large-scale projects. use. This shows that there is no bottleneck in the display of high-definition video surveillance.
Fourth, the standard H. 264 compression technology to enhance video management center platform compatibility:
Most of the current monitoring platform systems in the domestic surveillance market are based on the traditional DVR and NVS (or DVS) infrastructure. Many people think that these platforms need to spend a huge amount of overhead to be compatible with megapixel image management. In fact, HD or not only imposes higher requirements on data volume and image decoding capability, but also affects front-end codec devices, network bandwidth, and storage devices. In a sense, the platform's ability to support high-definition is related to the architecture of the platform. The better the system architecture is, the lower the cost of accessing new products will be. In addition, some IP camera manufacturers can also provide high-definition video surveillance management platform.
At this stage, the mainstream compression technology is the standard H. 264 compression algorithm, using this algorithm not only has good picture quality, but also has a low code stream, and more importantly, standard H. The 264-format video files can be decoded and played using standard decoders (such as Storm Video, VLC, MPC, KMPlayer, etc.), and the versatility and compatibility of devices are greatly improved. In a sense, it can be said that the standard H. 264 solves the problem of video data file compatibility that plagues the entire security community.
For the HD video image decoding capability that users generally care about, the current dual-core PC can basically decode 4 channels of 720P (30fps, 3Mbps stream) or 1 channel of 1080P (30fps, 6Mbps stream). Currently, there are already 1080P, 720P, and FullD1 fully compatible hardware decoders provided by mainstream IP camera manufacturers, enabling high-definition video decoding output controlled by the management center platform. In addition, the latest technology of mainstream IP camera manufacturers can already use video card hardware decoding core to complete multi-channel high-definition real-time video decoding display on a PC.
The traditional monitoring model can no longer meet the security needs of the government's “Safe Cityâ€, financial system, higher education, supervision, prisons, and Wenbo, and the network video monitoring system featuring network, intelligence, digitization, and remoteness is Become a new application trend and form an efficient, safe, advanced network video surveillance system.
In the network video surveillance system, H. 264 coding compression algorithm has been successfully promoted, with the gradual recognition of users, the reduction of the price and the improvement of the function, it will inevitably usher in the era of high-definition network cameras to dominate the field of future video surveillance.
The first part of the development history of high-definition network camera, a description of high-definition megapixel network camera:
In this "HD" era, everywhere you can see products with HD "title", what is HD in the end? What is a megapixel network camera?
1, HD definition:
At present, the definition of high-definition only appears in the broadcasting industry. According to relevant standards, the general display ratio is 16:9, and at least the digital signals with 1080i (resolution of 1920×1080) can be resolved, or the number of scanning lines must be reached in both vertical and horizontal directions. The 720P digital signal can only be classified as a high-definition product if it meets or exceeds the above criteria.
2. Definition of HD megapixel network camera:
The HD megapixel network camera is a network camera capable of continuously acquiring a maximum resolution of more than 720P (1280*720) or more than a Full HD (1080P, resolution of 1920*1080) to a higher 2048×1536 picture at more than 12 FPS. Satisfying the high-definition index mentioned in the HD definition above, the vertical and horizontal directions of the scan lines all meet the requirements of the 720P digital signal, which can be understood as the megapixel level in HD products.
3, HD network camera operating characteristics:
High-definition network cameras are the source of high-quality imaging and monitoring systems. Digital acquisition is performed directly on the video (actual high-end digital sensors (CCD\CMOS), and most of them are on the market today.) High-definition encoding compression and IP encapsulation (that is, through The network module compresses analog signals into digital signals, and then uses IP networks to carry high-definition video streams to achieve real-time HD monitoring, recording, playback, and forwarding; its video chips are megapixel CCD and COMS sensors (currently The CCD sensor pixels of mainstream cameras are mostly 440,000 pixels, and more video information can be obtained. The monitor picture is clearer and natural.
Second, the advantages of HD megapixel network camera:
General megapixel network cameras have the following advantages over traditional analog cameras and ordinary network cameras:
1, high-definition, the use of megapixel sensor can obtain more video information, generally up to 1280 × 720, 1920 × 1080, 1280 × 1024, 1392 × 1024, 1628 × 1236 or even 2048 × 1536 resolution . (In the field of surveillance, the first two resolutions are mainly based on video surveillance for security surveillance, and the latter are mainly based on road capture. In actual project applications, 1920×1080 is often referred to as 1080P due to system cost and effect requirements. Take a picture of the road.)
2, the image display quality is higher, to better capture details.
3, progressive scan CCD / COMS (high-end digital CMOS with progressive scan, its price is even more expensive than the CCD) to make the screen clearer, natural and smooth; easy integration of intelligent analysis capabilities.
4, can support HDTV widescreen output mode (16:9), HDTV achieved a huge leap in image quality, which means a clearer image, better color fidelity and widescreen format.
NTSC and HDTV have different screen aspect ratios 5 and wider coverage. The same surveillance area can replace the existing multiple fixed-point cameras and an all-around camera, saving cable, installation and maintenance costs.
Third, the development process and trends of high-definition network cameras:
Closed-circuit monitoring systems have grown with the advent of television and video cameras. In the course of a short history of several decades, starting from the 1970s and 1980s, with the rise of the new technology revolution, microprocessors Further popularization and development, from the birth of black-and-white cameras to the introduction of high-definition cameras, the number of camera lines from 380 lines to the current high-definition camera lines can reach thousands of lines.
In the field of video surveillance, it has also evolved into the current stage of high-definition network cameras, where high-definition video is HDTV (High Definision TV). With the popularization and large-scale use of surveillance systems in the international market and the domestic market, people are demanding more and more images. From the very beginning, they can see images, and now they want clear images, and they can perform processing analysis in the future. High-definition image. Therefore, with the continuous development of the high-definition industry and the demand of users for high-definition video, Full HD has become a new trend in the development of the high-definition industry.
The second part of the type of HD network camera, the importance of the sensor (Sensor):
The camera sensor is divided into CCD and CMOS. The sharpness of the camera depends on the performance of the Sensor. Compared with the CMOS sensor, the CCD sensor is superior to COMS in terms of sensitivity, noise control, high-quality image output, and dynamic image performance.
The most important feature of CMOS cameras is that they can be integrated on the same chip of the image sensor as a single-chip camera that integrates all the camera's functional circuits. Compared with CCD cameras, CMOS cameras have the advantages of high integration, small size, low power consumption, high frame rate, fast read speed, simple manufacturing process, and low price. However, the CMOS camera has a fixed pattern of noise that affects the image quality. In the same size, the sensitivity of the CMOS camera is not as good as the shortcoming of the CCD camera.
Second, HD megapixel network camera transmission, encoding compression method:
1. Today, HD megapixel network camera generally has two kinds of signal transmission: one is Mono/RAW transmission, and it is directly converted to a digital signal through an A/D converter chip. No compression encoding is performed on the network and the data is directly transmitted. It is transmitted to the computer and displayed on the computer by means of computer processing; the other is code transmission.
2, the current network camera encoding compression methods are:
(1), JPEG, MJPEG:
1, JPEG compression technology is the basis of all image compression technology, suitable for static image compression, direct processing of the entire picture, the compression ratio is 20-80 times, the resolution has no choice.
2. MJPEG (Motion JPEG) is a dynamic image compression technology developed on the basis of JPEG. It only compresses a certain frame, but basically does not consider the changes between different frames in the video stream. Later, there was a multi-layer JPEG (ML-JPEG) compression technique. Gradient technology was used to transfer low-resolution image files first, and then send more detailed compression data to improve the picture quality.
(2), MPEG-4:
MPEG-4 is mainly used in three areas, digital television, interactive graphics applications (including content synthesis technology), and interactive multimedia. Most megapixel network camera products at home and abroad generally use MJPEG/MPEG-4 video stream encoding and transmission. The advantages of MPEG4 in network video surveillance applications mainly include the following aspects:
1, saving storage space: video and audio fully synchronized 40M - 120M / Road / hour, is the same quality of MPEG1 or MJPEG 1/10; save storage hard drive cost investment and the later hard drive replacement costs.
2. Less occupied network transmission bandwidth: Since the compression ratio is more than ten times that of MPEG1 and MJEPG of the same quality, the bandwidth occupied by network transmission is 1/10 of the same quality of MPEG1 and MJEPG. For example, in the bandwidth of 64K, MPEG1 and MJEPG can only transmit 1/2 frame on average, while MPEG4 can transmit 5--7 frames, which will greatly save the rental fees for transmission lines.
3, error recovery ability: When the network transmission error or packet loss phenomenon, MPEG4 affected little and can quickly recover. If the error reaches 1%, MPEG1 can no longer play, but MPEG4 will only have a slight edge blur; Another example is when the network transmission by the instantaneous packet loss phenomenon, MPEG1 recovery takes at least 10 seconds, while MPEG4 only requires 1 ~ 3 seconds.
4, high image quality: can achieve close to the effect of DVD.
5. Variable bandwidth: The network output rate is adjustable from 56K--384K.
(3), H. 264: Today's mainstream video compression format.
H. 264 is a new generation of video compression format developed by the International Telecommunications Union (iTU-T). H. The most valuable part of 264 is the higher data compression ratio. In the same image quality, H. The data compression ratio of 264 can be 2 to 3 times higher than the MPEG-2 used in current DVD systems and 1.5 to 2 times higher than MPEG-4. Because of this, after H. 264 compressed video data requires less bandwidth and is more economical during network transmission. Currently H. 264 has been adopted by DVD Forum and Blu-ray Disc Association, becoming the standard for the new generation of HD DVD, but H. The 264 decoding algorithm is more complex and the computational requirements are even higher than WMA-HD.
The third part of the HD network camera selection considerations First, security surveillance camera selection:
In the video surveillance system, the lens selection of a megapixel HD network camera is also very important. There are various types of security surveillance cameras, and the specifications are also dazzling. It is very important to select a suitable lens in the surveillance project. In the selection of high-definition webcam lenses, the following manual and automatic two aperture lenses are recommended:
1, manual iris lens:
Specifications: Computar lens, M1214-MP, 2/3 "C mount, 12mm/F1.4.
2, automatic iris lens:
Specifications: Fujinon Fujinon, DV3.4X3.8SA-SA1L, 1/2†C mount, 3.8 to 13mm/F1.4, YV4.3X2.8SA-SA2L, 1/3†CS mount, 2.8 to 12mm/F1. 4.
Second, when buying the lens attention to factors:
1, to prevent fakes when buying.
2, to match with the camera, especially the flux F value matching, so that the camera can achieve the desired sensitivity.
3, megapixel camera generally have to buy matching corresponding megapixel lens.
4, look at the appearance of the material, whether with the CMOS / CCD specifications and interface matching to see whether the coating is good, look at the lens type (spherical / aspherical).
5, the application of environmental considerations, the lens type involves the selection of wide-angle lens, standard lens, telephoto lens, zoom lens, fixed-focus lens.
6, personally test the lens quality.
Third, high-definition megapixel network camera purchase points:
From the perspective of high-definition megapixel network cameras introduced in the current domestic market, the compression methods used are mainly MJPEG/MPEG4 and H. 264 is dominant, but there is no clearer quantitative data in terms of its bandwidth and transmission rate. Although the user knows its super high image quality, it still needs the image continuity and transmission under such a high image quality. The bandwidth is doubtful. Therefore, these products need to pay attention to the following points when choosing:
1. Accurately understand the quantitative indicators such as actual bandwidth and transmission rate under high-quality images, and conduct scientific assessment of the project's network resources.
2, using CCD or COMS sensor chip? If the CCD chip scheme, what kind of (single-channel/multi-channel) "output balance" technology is used, does the frame rate meet the actual demand.
3, the cooperation of the optical lens must be matched with the use of industrial-grade million lens or can not reflect the high-definition picture quality advantages of the camera.
4, fully examine the actual performance of such products in low light conditions, in particular, what technology manufacturers use to compensate for low-light imaging.
5, to examine the software features of such products.
The fourth part of the application of high-definition network cameras from the user point of view, urban security monitoring, transportation, airports, financial and other industries users, they have an urgent need for high-definition video images, and the cost of users for the construction of investment is a psychological preparation, the user What concerns is not the financial issue, but whether the HD system provided by the manufacturer can meet the user's expectations.
First, the development of new network technologies provides bandwidth guarantee for megapixel HD transmission:
Safe cities, financial network monitoring and other projects use self-built optical network or local area network to achieve 1000M bandwidth network. This Gigabit bandwidth resource is installed in the front-end of the above-mentioned 200 720P megapixel full-real-time HD cameras (occupying 3Mbps per channel), occupying 60%-80% of the total bandwidth resources (200 channels of 720P may not appear in actual projects. At the same time decoding on the wall, involving the cost of decoding on the wall, more than 50% to 100% of the points in the CIF format decoding on the wall or 1/5 to 1/3 points to decode the wall), so Gigabit network is fully effective support . In the application of high-definition network projects, many megapixel HD cameras are installed at key area monitoring points, and other monitoring points are based on the standard H. 264 compression algorithm Full D1 SD network camera or traditional analog + encoder mode access. Such as bank vaults, important traffic intersections and bays or gates, accidents or frequent occurrence of cases can be equipped with megapixel HD cameras, so that key events, on-site situations in key locations have HD images can be adjusted. The adoption of a megapixel high-definition and standard definition hybrid networking method not only saves equipment costs, but also effectively saves network bandwidth resources. Both the practicality and economy of the system can be perfectly combined to fully satisfy the cost-effectiveness requirements of users. (Note: The actual stable bandwidth of a Gigabit fiber is about 400M. If it is too high, such as 500M, 600M will easily lead to network failure. The actual bandwidth of the above-mentioned 200-channel 720P to the back-end core switch can reach 650M-800M. Gigabit network can actually carry 2-10 Gigabits to a core switch and the actual project is not likely to have a 200 Gb 720P with only one Gigabit fiber, and it is impossible for engineers and engineers to design such a transmission. If the above 200 channels are converted to 1080P and the video bandwidth is calculated by 5M or even a high standard of 6M each, the bandwidth design of the entire transmission network almost needs to be doubled, and the cost is almost doubled, which is why the market is now 1080P can be called loudly, but in the actual project, only the public security monitoring class invested by the government, especially the illegal use of the road, has captured the biggest reason that the project with profitability is widely used.)
As for public network transmission, megapixel HD network cameras support dual-stream technology, such as supporting 1080P+720P+D1+CIF full-real-time dual stream, so that they can use 720P/1080P HD applications locally, and use D1+CIF for remote users to call remotely. In other words, although the current ADSL wide area network technology can not support large-scale megapixel HD network cameras, it can meet the different needs of local and remote users through dual-stream technology.
Second, the development of mass storage technology makes storage no longer a bottleneck for megapixel HD applications:
As described before, based on the standard H. 264 compression technology, high-definition network camera, all the way 720P HD full real-time image stream is 3Mbps, video storage space required for an hour is about 1.35G or so (if 1080P, video recording is usually calculated according to 5Mbps, one hour requires 2.25G); Often, users often ask: A megapixel camera needs such a large storage space, how many megapixels? In fact, a megapixel HD camera can replace many ordinary cameras. With high-resolution image quality, the storage of videos will become more valuable (policy-based surveillance systems, and 90% of the final results are based on high-definition video playback).
Network storage systems (including storage servers and storage devices) are required for high definition image recording of high definition network cameras. The main connection methods of storage servers and storage devices are DAS direct connection, NAS network hard disk, and SAN (FC SAN and IP SAN) storage area networks. IP SAN uses IP architecture for Ethernet transmission and has good scalability and sharing. And lower application costs for allocation are one of the major technologies currently used for large and medium-sized centralized monitoring and storage. On the other hand, the mainstream data hard disk capacity used in IT has been terabytes or more, and the price of 2TB data hard disks has been popularized (calculated at an hourly data volume of 1.35G, a 1TB (actually available about 920G) data hard disk can store approximately 720P. 680 hours of video images or 1 hour of video recorded by 680 cameras).
Third, the LCD monitor has become the new favorite of high-definition video surveillance:
The high-definition surveillance industry does not have its own standards, so currently the major HD network camera manufacturers are all referring to the HDTV HDTV technology standards. There are two internationally recognized standards for HD: the video vertical resolution is 720p or 1080i; the video aspect ratio is 16:9. In the past few years, driven by the consumer electronics market, coupled with the shift of CRT TVs to liquid crystal and plasma TV screens, HDTV has achieved great success. Currently, the mainstream LCD monitors on the market are 21.5′′ and 24′′ with a resolution of 1920×1080. They can be compatible with point-to-point 720p and 1080p full HD video displays in the 16:9 format. The mainstream size of LCD TVs is 42′′, which is also the standard display size of 1080P HD. These LCD monitors and LCD TVs have high-definition interfaces such as YPbPr and HDMI, which meet the requirements of high-definition network camera video display. Some mainstream manufacturers' panels can reach 5ms or even higher 2ms, which is enough to meet the image refresh requirements of 25fps ~ 30fps.
Fortunately, security HD LCD monitors also followed closely and achieved rapid development. Some LCDs based on DID technology have the advantages of ultra-lightweight, low power consumption, high contrast, no flicker, low cost, etc., and have promoted its application in the field of security monitoring, especially in the video walls of command centers of some large-scale projects. use. This shows that there is no bottleneck in the display of high-definition video surveillance.
Fourth, the standard H. 264 compression technology to enhance video management center platform compatibility:
Most of the current monitoring platform systems in the domestic surveillance market are based on the traditional DVR and NVS (or DVS) infrastructure. Many people think that these platforms need to spend a huge amount of overhead to be compatible with megapixel image management. In fact, HD or not only imposes higher requirements on data volume and image decoding capability, but also affects front-end codec devices, network bandwidth, and storage devices. In a sense, the platform's ability to support high-definition is related to the architecture of the platform. The better the system architecture is, the lower the cost of accessing new products will be. In addition, some IP camera manufacturers can also provide high-definition video surveillance management platform.
At this stage, the mainstream compression technology is the standard H. 264 compression algorithm, using this algorithm not only has good picture quality, but also has a low code stream, and more importantly, standard H. The 264-format video files can be decoded and played using standard decoders (such as Storm Video, VLC, MPC, KMPlayer, etc.), and the versatility and compatibility of devices are greatly improved. In a sense, it can be said that the standard H. 264 solves the problem of video data file compatibility that plagues the entire security community.
For the HD video image decoding capability that users generally care about, the current dual-core PC can basically decode 4 channels of 720P (30fps, 3Mbps stream) or 1 channel of 1080P (30fps, 6Mbps stream). Currently, there are already 1080P, 720P, and FullD1 fully compatible hardware decoders provided by mainstream IP camera manufacturers, enabling high-definition video decoding output controlled by the management center platform. In addition, the latest technology of mainstream IP camera manufacturers can already use video card hardware decoding core to complete multi-channel high-definition real-time video decoding display on a PC.
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