In the IP security technology market, high-definition analog video surveillance systems are in serious competition. These are AHD, HD-CVI, HD-TVI standards. They have been developed by various video surveillance device manufacturers independently of each other. The task was solved, now the end user, who has an analog video surveillance system installed, can significantly improve the quality of the resulting image from 600 TVL to 1080p without replacing cable networks.
When creating new standards, the following goals were set for the developers:
- Significantly improve image quality, making it comparable to megapixel resolution;
- Increase the transmission distance of an analog signal without reducing its quality, without using an additional amplification device;
- Affordable cost for the end user compared to the main competitor of IP devices;
- Possibility of installation on old coaxial cables, ease of installation and configuration;
- Solving the problem of video signal delay when transmitting over long distances.
HD-TVI
It was developed by Hikvision in 2012. Transmits 720/1080p high definition image over standard coaxial cable. It is a promising development with great potential. This technology allows not only to transfer the image from the camera to the DVR, but also to control PTZ devices, receive an audio signal, control various functions (BLC, WDR, DNR) through the OSD menu of the camera directly from the DVR. Most of the DVRs manufactured by Hikvision are hybrid. Several IP cameras can be connected to them via a digital
information transmission channel.
TVI is an open source technology, but its widespread adoption is still highly dependent on Hikvision's investment efforts. In addition, the cost of these products is slightly higher than the standard budget solutions for video surveillance systems using AHD technology, which have recently become quite widespread.
AHD
The AHD analog high-definition system was first introduced to the Korean developers of the Nextchip video surveillance chipset in 2013. The standard has open source and thanks to the friendly policy of the company, products with his support are produced by many enterprises. Image transmission is carried out via a conventional coaxial cable, in addition, this standard opinion is demanding on its quality. The principle of operation and the main advantage of the standard is that when receiving a signal from a photosensitive cds matrices, the processor of the video camera performs the separation of digital streams describing the brightness and color of the image. This allows for digital image processing using all available functions. Then the cable is used to transmit command pulses for the ptz drive, manual control of the IR illumination, and broadcast the audio signal.
On this moment CCTV devices with AHD support are produced in more than 50 factories in China and South Korea. At the same time, the development and further modernization of the standard is carried out independently at each enterprise. This gives impetus to the rapid development of technology. A rather high competition has an impact on lower prices.
HD-CVI
A high-definition composite video interface introduced by Dahua in 2012. The standard is capable of transmitting video High Quality in not compressed format with resolution up to 1920x1080p. The same channel transmits audio and commands to control OSD functions and PTZ devices. The technology has become less widespread due to the use of only licensed chips produced by the company.
IMPORTANT! As a rule, Dahua implements ready-made solutions for video surveillance systems. Having purchased the company's products once, the user is forced to continue to resort to its services and use original devices. This significantly reduces the freedom of choice. And given that the cost of the company's products is slightly higher than that of competitors, the cost of modernization existing system CCTV can exceed the installation of a new one.
Brief description of the standards
After analyzing the data presented in the table, we can come to the following conclusions. All three technologies have common features that significantly improve the performance of high-definition analog cameras:
- Signal transmission without significant losses over significant distances, comparable or exceeding the transmission of packetized information over a cable twisted pair;
- The use of old coaxial cable networks not only for broadcasting high-definition video, but also for transmitting audio streams, information signals to control OSD / PTZ devices;
- There are no problems with bandwidth excess, signal delay or lost transmitted packets as in IP technologies;
- The chipset of each analog standard supports progressive scanning.
At the same time, the presented technologies also have certain differences, which are reflected not only in video cameras and related equipment, but also in the policy of manufacturing companies and the features of promoting products on the security systems market.
Code Availability. The HD-CVI technology is proprietary, which means that Dahua has closed the ability to make adjustments to the chipset code. It acts as a major manufacturer of devices for video surveillance systems, and presents on the market a wide range of products that are self-sufficient, but incompatible with other formats. TVI and AHD took a different path and opened up the format, allowing any chipset manufacturer to produce such products. This gave significant advantages in the variety of products, their characteristics, areas of use and made the pricing policy more competitive and customer-oriented.
Compatible with older video image transfer formats. Modernization of many video surveillance networks is carried out according to the residual principle. New devices are acquired gradually and must be fully compatible with those already working. However, old-style DVRs do not support new high-definition technologies. Therefore, before buying and installing such cameras, you must replace the DVR. Devices that support AHD technology are fully compatible with the old 960H and D1 formats, they can receive and record information from outdated cameras. HD-TVI technology can only support 960H format, subject to the purchase and installation of an additional chipset, which slightly increases the cost of such DVRs.
Distribution of the standard. CVI technology was the first high-definition analog standard to be introduced to the market. However, Dahua products are positioned in a high price range and due to the high cost, they have not won a key position in the video surveillance market. At the moment, the most common is the AHD standard. According to the rating, which is published in the Internet resource dedicated to security systems ASMAG Security 50, the AHD standard is supported by more than 35% of manufacturing companies. In addition, the price of such equipment is quite comparable in cost to CCTV standard products. Hikvision's TVI standard also has a similar policy of openness. At the moment, many manufacturers of equipment for video surveillance systems combine the ability to connect both formats in their products. Giving ample opportunities for compatibility when selecting devices from different manufacturers.
Features of practical use
The distance over which an analog signal is transmitted without loss of quality and the use of various amplifiers and transceivers in the new standards is 500 m. Despite the fact that a twisted pair cable without additional devices is capable of transmitting information without distorting it at a distance of no more than 100 m, and the old analog formats were limited to 150 m. All manufacturers recommend using only high quality coaxial cable RG-59 or its domestic counterpart RK 75-5. At the same time, the HD-CVI standard demonstrates the highest resistance to external interference. AHD with insufficient cable quality can spontaneously switch to the transmission of a black and white image. And HD-TVI devices may stop transmitting the image at all.
All the presented standards regulate the transmission of not only images, but also audio data, commands to control various remote devices. In fact, this equalizes the capabilities of IP technologies and high-definition analog video surveillance systems, giving the latter the opportunity to use them in access control management systems.
However, in practice, the HD-TVI standard lags behind its main competitors in terms of functionality. At the moment, it implements the possibility of two-way video signal transmission and control of remote devices via the rs485 protocol.
An important factor in the creation of video surveillance systems is the ability to use both ip-cameras and analog ones. The hybrid connection is fully implemented in the AHD and CVI standards, where the receiving chip provides support for the required formats. This allows you to connect different types of cameras in one network at no additional cost. Moreover, the creators of the AHD standard went even further by implementing the ability to connect all three types of video cameras: IP, high-definition and outdated CCTV (PAL).
Cost for many users is a fundamental factor when purchasing video surveillance devices. Initially, the price for all three standards was comparable and quite high. At the moment, more than 30 leading enterprises in China and North Korea are involved in the production, which has significantly reduced the cost of production. The most affordable are products of the AHD standard. Dahua products are 5-15% more expensive, which almost exclusively produces devices supporting CVI. TVI standard equipment is currently considered the most expensive, on average 15-20% more expensive than similar functionality AHD devices. However, active promotion in the market and support by the Hikvision developer company leads to a constant decrease in cost.
New turnkey solutions
- Ready-made video surveillance kit consisting of Dahua HDW1000RP cameras and Dahua DHI-HCVR4108C-S2 video recorder.
It is a standardized solution for use in a private home, office, small business, etc. In fact, this is a scalable system in which the number of cameras can vary from 3 to 8. At the same time, it is not advisable to purchase DHI-HCVR4103(4.6)C-S2 DVRs, as this seriously limits the expansion of the system.
- A ready-made HD-TVI video surveillance kit based on the HiWatch DS-H104G recorder.
In this case, it is possible to select a video camera 4 various types: Two domes for indoor use and two for outdoor use.
- A ready-made video surveillance kit for 8 cameras that supports AHD technology.
Manufactured by the Chinese company Cantonk. The kit includes a T9708 video recorder, it is possible to select and connect any video cameras from this manufacturer.
AHD
Despite the fact that analog video surveillance systems are limited by the generally accepted standard for PAL color television systems (with a vertical capacity of 625TVL), their potential is far from being exhausted.
Recently, there have been trends to increase the horizontal resolution of analog cameras by introducing higher resolution matrices, and to ensure the transmission of the signal generated by such an analog camera, the line length was increased - this is how the 960H standard was born, which remained the same PAL in vertical resolution. But cameras with a resolution higher than 700TVL, for example, in 1000TVL, 1200TVL, have nothing to do with vertical television lines, these values are subjective and depend on the type of matrix used, namely on its horizontal resolution.
To be able to transmit more information about a video frame, it is necessary to move away from the generally accepted PAL / SECAM / NTSC standards. Modern development computer science made it possible to perform resource-intensive calculations at previously unimaginable speeds, which in turn allows the use of complex mathematical algorithms for digital signal processing.
The results of work to increase the resolution and throughput of analog video surveillance systems have become the AHD - Analog standards high definition- High definition analog systems .
Compared to its analog predecessors, the AHD analog standard provides better color reproduction and greater image spatial resolution.
Facilities built for analog video surveillance systems can be upgraded to analog HD systems by replacing PAL/960H standard cameras and DVRs with new AHD standard cameras and DVRs, without the need for new cable installation work.
This standard uses a data transmission medium familiar to analog systems - an ordinary coaxial cable, and is less demanding on the quality of the cable than the HD-SDI digital standard. .
In addition, compared to PAL, the AHD standard uses carrier separation for colors and brightness, without the usual color subsampling, like Chroma and Luma for the PAL standard.
TVI
To date, a huge number of coaxial lines for connection have been deployed around the world. Due to the development of progress, more than half of these cameras will be replaced by more modern cameras with high resolution. The need to replace the cable greatly complicates the process, and the increase in the amount of the order in the estimate for the end user.
HDTVI is a state-of-the-art standard for transmitting 720P/1080P audio, video and control signals PTZ cameras over coaxial cable. The working distance when using this technology is about 500 meters. HDTVI technology can be considered an easier to install and use solution for high quality video surveillance.
Distinctive features of HD-TVI technology:
High quality picture - 720/1080P
-Transmission over coaxial cable of both audio / video signals and control signals
-There is no loss of image quality when transmitting HD signal
- Signal transmission distance of almost 500 meters
- It is not difficult to upgrade an analog system to HD-TVI.
HDCVI
1. Price: Comparing HD CVI and analog cameras, we see that the difference in price between the two tested products is about 15%. The difference in the price of a 4-channel recorder is almost the same, maybe even less.
2. Analog video signal. Both video standards used are analog. It seems that the use of analog equipment for video surveillance will be common for a long time due to its several advantages:
Low cost of equipment, reliability, signal transmission over long distances, ease of installation and configuration, which does not require special skills.
Well, about the advantages of HD-CVI technology over a simple analogue:
1. Image resolution. The declared resolution of HD CVI cameras is 720p or 1280×720, which is much higher than that of standard analog cameras - 700 TVL maximum.
2. Fully adapted to modern monitors. Almost all modern monitors have a 16:9 aspect ratio. The HD-CVI camera matrix uses exactly the same aspect ratio, which, in turn, allows you to see the picture without any distortion. The matrix of a standard analog camera has an aspect ratio of 4:3. It is generally accepted that this format is more correct for the implementation of security video surveillance. However, today, there are practically no 4:3 monitors left, or they have an unreasonably high price. Accordingly, a 4:3 picture when displayed on a 16:9 monitor will be deformed in one way or another.
3. Extended functionality. Progressive scan. With this technology, menu control and the transmission of audio and video signals occur over a single coaxial cable. The signal transmission range without amplification is about 500 m.
Let's summarize in the comparison table below.
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HD-TVI |
HD-SDI |
HD-AHD |
HD - CVI |
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Full name and spelling |
High Definition Transport Video Interface - a video interface developed by techpoint, based on the conversion digital signals to analog and transmit it via coaxial cable, which extends the transmission range and reduces the cost |
High-Definition Serial Digital Interface this technology in video surveillance systems from HDTV - high definition television. In other words, HDSDI is a standard for high image quality. |
Analog High Definition is a new, revolutionary technology in the field of technical security equipment, the capabilities of which far exceed those currently available, AHD technology allows video, audio, and control signals to be transmitted over a single coaxial cable! |
High Definition Composite Video Interface - The interface consists of high definition video, this technology adds HD image quality to the features of analog devices and provides a customizable solution for all kinds of video surveillance requirements and applications |
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Common to all standards |
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CVI TVI AHD all these standards are extensions of the progressive scan analog high definition video based on coaxial cable |
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Operation is the same as traditional analog devices, easy to replace equipment, cameras and dvr |
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Long range signal transmission at a distance without signal loss, delays. |
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Video resolution |
1080p/720p |
1080p/720p |
1080p/720p |
1080p/720p |
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Transmission delay |
No |
No |
No |
No |
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Transmission distance (without repeater) |
500 |
150 |
500 |
500 |
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RS-485 coax control |
Yes |
Yes, but additional hardware is required |
Yes |
Yes |
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Price |
Low |
High |
low |
low |
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Noise immunity |
High |
Low |
high |
high |
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Transmission reliability |
High |
Low |
high |
high |
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Chipset |
US Professional 3rd Party Chipset vendor |
SD/HD/3G-SDI |
Nextchip |
Dahua |
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Your name HD-CVI format analog video transmission was obtained thanks to the technology of direct transmission and quadrature amplitude modulation, the use of which avoids crosstalk distortion of the CVBS composite video signal. At the same time, the luminance and chrominance signals are completely separated, while maintaining the quality of the video during transmission. The technology is owned by Dahua.
HD-CVI includes a set of chips: transmitting - TX and receiving RX chip, designed for DVRs and video cameras, used for data processing.
It is recommended to use cables 75-5 and 75-3 HDCVI allows you to transmit a Full HD video signal 1080P (1920 ×1080) without distortion at a distance of 300 meters for cable PK-75-3 or 400 meters for PK-75-5, and the signal 720P (1280 ×720) at a distance of 500 meters using cable RK-75-3 or up to 650 meters with RK-75-5.
For building video surveillance systems HD-CVI cameras and digital HDCVI video recorders are used using the high-definition video signal standard. The system has a star topology structure: the DVR is a node for point-to-point signal transmission to the camera via coaxial cable. HD-CVI technology supports two HD video formats: 1080p (1920 ×1080) and 720p (1280 ×720). The technology is equipped with the function of automatic signal correction (ASC), which practically does not allow signal distortion when transmitting over a long distance.
Compared to IP video surveillance, HD-CVI systems do not use encoding/decoding of transmitted/received signals from analog to digital format and vice versa, as a result, a megapixel video image from HD-CVI cameras Dahua surveillance is transmitted to the DVR with zero delay.
Signal in HD-CVI video surveillance systems transmitted at frequencies below 50 MHz and is much more resistant to interference than using, for example, HD-SDI technology.
HD-CVI combines video, audio, and control signals and then transmits them over a single coaxial cable, simplifying the entire system.
To further implement the transmission of multiple signals over a single cable, audio signals and two-way data signals are placed in the signal attenuation zone. Thus, synchronization with the video signal is enhanced, and thanks to automatic signal correction, a maximum sampling frequency of 44.1 kHz is maintained.
Comparison of HD-CVI and IP cameras
Benefits.
IP cameras cannot transmit video over a distance of more than 100 meters without the use of additional devices. HD-CVI format can transmit video at 500 meters without the use of additional. devices via coaxial cable or network cable.
IP cameras require a specific (Not low) bandwidth in the network and there may be delays and losses in the video stream, as well as conflicts with other IP equipment. HD-CVI cameras do not have problems with delays or loss of video stream.
HD-CVI technology is much cheaper than IP cameras and NVRs.
IP cameras cannot transmit video over coaxial cable natively (without additional converters), for which networks must be built using a network cable or optical fiber.
Flaws.
IP cameras are capable of higher resolutions than 1080p and available resolutions will continue to grow in the future.
IP cameras are capable of being powered by a network cable (POE), which does not require additional cable systems to power the cameras.
If there is an existing network infrastructure and throughput network is large enough, you can add additional IP cameras to existing network without creating new infrastructure.
Comparison of HD-CVI and HD-SDI technologies
The HD-SDI network is limited to 150-250 meters for video transmission. HD-CVI can be transmitted up to 500 meters and even a little more (720p).
HDCVI, unlike HD-SDI technology, is well protected from electromagnetic interference by another encoding method, separating luminance and color signals in a special way.
HDCVI technology equipment significantly cheaper than HD-SDI.
Less than a year has passed since the announcement of the creation new system video surveillance, or rather, a new format of high-definition television (High Definition), but with an analog signal transmission method. The development company had remarkable courage to take responsibility for promoting a new format in the video surveillance industry.
Nikolai Chura
Technical consultant of VideoSCAN Firm LLC
The basic parameters of the new format correspond to the standard values of 720p and 1080p. This format assumes a horizontal resolution of 800 and 1200 TVL with a 16:9 aspect ratio in progressive resolution. At first it seemed that the format would be monopolized by the patent owner. However, in our time, when "everything has already been invented", it is not possible to keep anything to one manufacturer. Technical solutions are created today by compiling integrated solutions, developed for the most part by large global manufacturers. In addition, the main technical solutions developed many years ago. Ultimately, the first HD television was still analog, and many of the problems of those years are now successfully solved thanks to the modern element base of large integration with high performance.
Comparison of competitive HD technologies
The loneliness of Dahua, the developer and patent holder, did not last long. Three competing companies have already emerged, not counting the major creator of the NextChip element base, which have similar developments. Formally, three technologies with very similar characteristics are proposed. These are HD-CVI (High Definition Coaxial Video Interface) from Dahua and HD-TVI (High Definition Transport Video Interface) from Hikvision and Hi Sharp. Hi Sharp also manufactures AHD (Analog High Definition) cameras, which are almost identical to HD-TVI. Apparently, in them Hi Sharp uses the element base of NextChip, which is the creator of the technology and the very term AHD. And most likely it is the fact of the production of the element base that gives grounds to declare the continuity of the AHD technology for third parties. On fig. 1 shows the general structural scheme new system.
Despite the fact that both HD resolutions (720p and 1080p) are declared for all technologies, in reality FullHD cameras are produced so far only by Dahua and Hikvision. No wonder these two "titans" are the main competitors in China. Format differences are shown in the table.
It can be seen from the table that it is very difficult to talk about differences in this case. Each of the developers offers a comparative analysis of the characteristics of all formats used in video surveillance. In them, of course, new format demonstrates significant merits, and studying the differences and features can bring a lot of joy to specialists. For example, IP and SDI systems lose significantly in terms of analog output resolution, although it is not entirely correct to compare the parameters of possible technological (auxiliary) outputs. The cheapness of the cable for CVI, similar to typical analog CCTV, is obvious. However, as practice shows, CVI requires a cable that is almost identical to the SDI system, especially considering the declared range. At the same time, savings are obtained only in the absence of repeaters at a distance of more than 100 m, as in SDI. The main comparative factor at present is the transmission range of the signal. But in relation to the analog transmission method, it is not always correct to talk about the transmission range. For digital signals, synchronization capability or burst rate-limiting errors are the determining factor, so you can determine the transmission distance for each type of cable quite accurately. In the case of analog transmission, the image quality deteriorates noticeably while maintaining a fairly confident synchronization, so it is rather difficult to determine the maximum cable length without taking into account changes in color reproduction and resolution of the resulting image.
Another banner under which the "revolution" of video surveillance is going on is the transmission of a high-quality FullHD image by analog method over a conventional coaxial cable at 500 m. Under this "sauce", many managers report that the HD-SDI format with its 100 m is something that is outdated and obsolete. Yes, we can already state that the excessive quality of professional-class HD-SDI images is practically not demanded by the security market due to the high price of equipment. If the digital transmission "pixel for pixel" of an uncompressed image in television centers and between them is an indispensable condition for maintaining a common quality standard, then in video surveillance this turned out to be an overkill that does not cover other emerging difficulties. On fig. Figure 2 shows enlarged fragments of the measurement table extracted from images of HD-SDI and HD-CVI systems for FullHD cameras.
Horizontal resolution can be estimated at 1000-1050 TVL for HD-SDI and 900-950 TVL for HD-CVI. The cameras are connected with short cables of 1 m. Please note that the results are cumulative for cameras and recorders with H.264 compression codec (unknown) and reformatting from format to format on output. We can assume that this is a systemic result.
Unfortunately, the relatively modern table used in the tests with the presence of measuring elements of more than 600 TVL not only has a 4:3 format, but also overestimates the horizontal resolution by about 20%. This became clear when comparing the geometry of a 600 TVL fragment with a television table of 1972 from the Moscow Television Center, where this resolution is maximum. Therefore, the obtained estimates must be multiplied by 1.33 to bring the resolution to a 16:9 format, and additionally multiplied by 0.8 to correct for a positive error. The resulting correction factor of 1.064 indicates that in this case, you can focus on the direct data of the table
Disadvantages of High Definition Format
Is everything so cloudless in the new HD-CVI format (aka TVI, aka AHD)? Even at the beginning of the "hard way" HD-SDI also talked about the usual coaxial cable from old system video surveillance. Perhaps for the USA or Western Europe, where this cable is at worst RG-59, and most often RG-6, this is true. In Russia, these cables, as a rule, are KVK-3, KVK-2 or KVT-2, but there is also a shielded wire ShGES-2 or 4, so you can’t expect “miracles” and even simple operation.
The 3C and 5C cables required by the developers are close to the common standard models RG-59 and RG-6. We can say that for the Russian reality it is no longer quite "any RK-75", as the manufacturer claims. Moreover, these are quite worthy options for an HD-SDI system with a bandwidth of 1.5 GHz and a carrier frequency of the pulse sequence of 750 MHz.
The spectrum of the analog video signal CVI (TVI or AHD), even for FullHD, does not exceed 26 MHz, which is not impossible for a coaxial cable, usually rated up to 1000 MHz. At the same time, this exceeds the spectrum of a typical television signal by more than 4 times and imposes somewhat increased requirements on communication cables.
On fig. 3 enlarged fragments of the wedge for evaluating the horizontal resolution of the CVI FullHD image during transmission via cable RK-75-4-361, an analogue of RG-6 with a length of 0, 500 and 890 m, as well as a combined cable KVK-2-2P and KVK-2 Rexant with a length of 200 m.
Oddly enough, the image clarity with a cable of 500 m is even slightly higher than with a length of 1 m. Even for a cheap Rexant cable, the resolution does not decrease to 800 TVL and at a distance of 200 m. But with an increase in line loss, color reproduction changes dramatically, which is illustrated rice. 4. Obviously, it is undesirable to increase the range beyond 500 m even with a good cable, and cheap cables should not be used longer than 75–100 m.
It is noteworthy that the camera control is also broken when the cable length is more than 500 m. This is a rather difficult to explain technical phenomenon that characterizes the complete secrecy of information about the principles of data transmission.
Strictly speaking, the promises to provide 1920x1080p resolution and normalization as 1080p resolution of HD-CVI cameras and recorders, as well as similar HD-TVI and AHD, are fundamentally unrealistic. The system is switching to an analog signal with the conversion of brightness to amplitude and the transmission of chrominance by quadrature subcarrier modulation, according to the principle of operation is almost similar to the PAL standard, with subsequent conversion of the essentially composite signal to digital form for recording and output in HDMI format. This violates the pixel-to-pixel principle and forces the HD-CVI system resolution to be evaluated as analog systems– only in television lines. In addition, additional transformations "analogue-digital-analog-digital", if performed incorrectly, can cause artifacts and moiré. You should also be wary of the developers' statements about the "high security" of analog transmission of HD-image by amplitude modulation over a coaxial cable. The coaxial cable is poorly protected up to 5-10 MHz, and the transmission of information by changing the amplitude is the most sensitive transmission method to interference. In all likelihood, HD-CVI should be similar in sensitivity to interference to typical analog CCTV.
Summarizing the above, we can conclude that the new format (CVI, TVI or AHD) for video surveillance is promising, if, of course, the price of equipment is significantly lower than that of HD-SDI systems. But, unfortunately, only an increase in the image transmission range, which, simultaneously with the transition to analog, led to some decrease in its quality, will not make the new format or formats particularly attractive.
In 2014, the CCTV market met with great expectations emergence of new formats HDCVI, AHD and somewhat later HDTVI. The fact is that their predecessor format HD video surveillance HD-SDI impressed many with its picture quality, after the traditional analog picture. It also had significant shortcomings that prevented it from becoming widespread. This is the high cost of video recorders, cameras, high requirements for the cable network, limited by the length of 70-100 meters. Everything about it was good except for the price and inconvenience of use.
Essential for the emergence of such formats was also the desire to use the coaxial networks available to consumers, the traditional nature and simplicity of the method for all system installers, in contrast to ip video surveillance systems. Technological progress also plays its role - the emergence of high-capacity HDD drives necessary for recording heavy HD video.
The CCTV market demanded HD 720p, FullHD 1080p and high definition HDTV, which had already become commonplace in everyday life, available without the restrictions of SDI transmission.
In an effort to overcome these shortcomings and make HD video surveillance affordable, the well-known Dahua company is developing its HD-CVI standard for transmitting HD signals over coaxial networks using a coding system. HD-CVI made it possible to transmit a signal over 350-500 meters without loss of quality, depending on the quality of the cable.
Soon, the Korean company NextChip announced the appearance of its AHD format and, with some lag, competing with them Hikvision with HD-TVI format.
Features of HD-CVI, AHD and HD-TVI formats.
The tests carried out showed the incompatibility of the new formats with each other. At their core, they remain analog, and therefore the quality of the cable, the cross section and length of the line affect the resolution and purity of the frame, its color. And in this, in comparison with the traditional analog signal PAL/NTSC HD-CVI, AHD and HD-TVI formats have a very significant advantage.
On the RG-59, which is similar to the domestic cable PK-75-3,7-32 (33,34,35), all Dahua, NextChip and Hikvision claim reliable 720p signal transmission over 500 meters without quality degradation, by the way, underestimating the data competitors. Tests fully confirm these data.
On a coaxial cable of the worst quality RK-75-3 and even more so RK-75-2, you can see the difference between HD-CVI, AHD and HD-TVI in the manifestation and reduction of characteristics. The HD-CVI format on the 500 meter section lost some resolution and clarity (minor noise). But the AHD video signal with the same resolution of 720p, lost color over the same length, transmitted, in fact, a black and white image. Under the same conditions, HD-TVI distorted and at times lost the image altogether.
An important innovation of the formats is the possibility of transmitting sound and telemetry signals over a single cable along with video by all developers.
Representatives of Dahua were the first to confirm and demonstrate the transmission of sound over a single cable in CVI format on working equipment. Not one of the companies has yet presented the transmission of telemetry data in serial equipment.
Compatibility with analog CVBS signal.
Differences are also found in compatibility with analog cameras and CVBS signal. So in AHD and HD-CVI equipment compatibility is built into the receiving input chip. In the HD-TVI format, such support is provided by an additional decoding device.
Resolution and prospects for its increase.
Introduced initially in 720p, all competing manufacturers have now mass-produced in 1080p. The first were representatives of Dahua with HD-CVI. In addition, the development and release of equipment with a resolution of 2048x1536 corresponding to 3 megapixels and even with a resolution of 4K is announced.
The cost of HD-CVI, AHD and HD-TVI equipment.
This factor is influenced by the marketing policy of companies. Dahua and Hikvision and NextChip. The prevailing equipment prices are as follows - AHD from NextChip is the most affordable and confidently competes with the old analog format. Somewhat more expensive (by 10%, justified by the quality of transmission and the implementation of the declared sound transmission) equipment Dahua HD CVI. A more significant difference with the AHD price leader is TVI equipment of about 20%.
Pricing is significantly affected by the promotion of sales of microchips of these manufacturers among other developers. Not surprisingly, the traditional supplier has been the most successful in this. electronic components NextChip and AHD.
Despite the fact that, in order to conquer the market, all manufacturers have opened their technologies to third-party developers, TVI technology is not so successful due to its higher cost.
In connection with the above, two conclusions arise. On leadership as a technology Dahua HD-CVI. However, in greater prevalence and pricing policy, the format is leading AHD by NextChip.
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