The two main players in the HD over coax transmission market are HDTVI and HD-CVI. There is a third, less well-known technology called AHD, which stands for analog HD. What is the difference between these technologies? We hope to help you understand the differences and benefits of these technologies.
HDTVI (High Definition Transport Video Interface) and HDCVI (High Definition Composite Video Interface)
HD-TVI technology was created in 2012 by a company called Techpoint with the support of Hikvision. It was created to compete with the technology that was under development by Dahua - HDCVI. Rumor has it that someone infiltrated Dahua with industrial spies, and as soon as they got the information, they formed a company called Techpoint. But it is unlikely that this information will ever be confirmed. Hikvision, the world's largest systems manufacturer backed by the Chinese government, supported Techpoint in this endeavor. This has been one of the biggest revolutions in the world of video surveillance since the creation of Internet protocol based surveillance cameras.
HDTVI technology, like HDCVI, is based on the same principles created by the television industry for high quality video transmission. The first such video surveillance technology was HD-SDI technology. However, SDI technology had serious limitations regarding signal transmission distance. This limitation has been corrected by the creation of two new technologies. HDTVI is capable of transmitting 1080p video at about three hundred meters, while HDCVI can transmit 720p video at five hundred meters and 1080p video at about the same distance of three hundred meters. There are other similarities as well as differences. We will provide you with the necessary information so that you can better understand how these two technologies work.
HDTVI , from the simplest to the most complex models, are capable of handling analog surveillance cameras, HDTVI cameras, Hikvision IP cameras and IP/HDTVI cameras. HDCVI DVRs, ranging from the basic model to the 16-channel hybrid model, can also process signals from analog surveillance cameras, HDCVI, Dahua IP cameras, ONVIF-enabled IP cameras, and others. As you can see, DVRs based on these technologies can handle three different technologies in one DVR, which makes them hybrid devices, or rather, tribrid ones. Tribrid DVRs can handle their native technologies as well as two other technologies. The main difference between these two technologies is that Dahua DVRs can also process video from other brands of IP cameras, while Hikvision TVI DVRs can only process Hikvision IP cameras.
To date, both companies offer several basic models of surveillance cameras that are compatible with their technologies. For example, you can buy fixed or varifocal domes or bullets based on both platforms, as well as the Pan Tilt Zoom. In the case of HDTVI technology, the development of various models of surveillance cameras has been slower. Dahua, in turn, has a very wide range of products available.
Conclusion
As you can see, there really isn't much of a difference between these two types of technology. However, the HDCVI output has a slightly more user-friendly interface. which will be convenient for beginners in the field of video surveillance.
Source: securitycameraking.com. The article was translated bysite administratorElena Ponomarenko
Its 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 the network bandwidth is large enough, then additional IP cameras can be added to the existing network without creating a 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.
Until recently, the demand for analog systems has steadily declined due to low resolution and increasing requirements for image quality. At the same time, the market is in no hurry to completely abandon analog systems, since they are easy to install and maintain, and installers do not need to retrain for other technologies. In this regard, new analog technologies began to appear on the security market to solve the problem of low resolution. One of them was TVI
Mikhail Plotnikov
Technical Director of LLC "Novikam"
Leading manufacturers of the CCTV market have developed three high-definition technologies to shake up the analog market: CVI, AHD and TVI. And today we will talk about HD-TVI (High Definition Transport Video Interface), or simply TVI (Turbo Video Interface).
The emergence of a new technology
TVI is the latest standard for transmitting 720p/1080p audio, video and PTZ camera control over coaxial cable up to 500m.
The technology was developed in 2014, and the products in which it is implemented have already appeared on the video surveillance market and brought the competitiveness of analog systems to a new level. At one time, the Sony IMX 138 sensor with an indecent number of TV lines succeeded in this, now it's time for the next step - increasing the resolution of analog systems to HD and Full HD.
TVI video equipment uses megapixel CMOS sensors, the signal from them is converted for transmission at a high frequency by a special Transmitting Chip, which is recognized by the Receiving Chip, and transmitted to the processor (Fig. 1).
The reception chip can automatically recognize the signal not only from TVI cameras, but also from other standard analog cameras.
Key differences
TVI cameras offer maximum image detail and improved color quality with the highest bandwidth of any of the three new HD technologies, up to 55 MHz. Moreover, the signal has a higher noise immunity compared to a conventional analog signal.
An important difference from standard analog technology is that TVI allows you to transmit control signals on the same line as the video signal to control the built-in menu and the movement of PTZ cameras. This control technology is called UTC and is a modern solution to replace RS-485.
The most important advantage of TVI technology is high resolution, and here no one will be disappointed - 720p and 1080p at 25 or 50 fps have already become the bar that any self-respecting manufacturer must keep. It was the low resolution of analog camcorders that forced consumers to switch to digital technology. TVI transmits video without delay in real time, and unlike IP systems, image frames cannot be lost due to network congestion.
Simple, convenient, profitable
TVI, while having the high resolution of digital systems, retains the simplicity and convenience of a standard analog system. The signal is successfully transmitted over both coaxial and UTP cables, which makes it possible to upgrade the video surveillance system to high resolution without laying new communications or create a new system, minimizing cable costs. Because the connection of TVI systems is identical to that of analog equipment, installation crews will be able to draw on a wealth of existing experience without the need for retraining. Moreover, the equipment at the site can be updated gradually, since the main link of the system - the video recorder - successfully works with conventional analog video cameras. The DVRs also support the connection of IP cameras, which provides great potential for video surveillance system design where analog, TVI and IP equipment can be combined into one system and recorded by one device.
A nice feature of TVI equipment is its cost, which is comparable to analog devices and many times cheaper than IP and HD-SDI systems. It should be taken into account that TVI, like other CCTV standards, is inconvenient for building very large systems, consisting, for example, of several hundred cameras. However, this is inherent in CVI, and SDI, and analogs. But for small and medium-sized systems (up to 100 cameras), the technology is ideal.
The cameras have basic analytics - motion detection and camera closure. More advanced smart features such as license plate recognition or face recognition can be implemented using external software.
"Second wind" analogue
If we think about the next stages of TVI development, then we can assume that the resolution of video cameras will be increased to 3 and 5 Mpx. TVI technology is built on an open platform, which allows many manufacturers to compete in the market for this equipment. For consumers, this is a winning formula – better quality and lower prices.
We compared the key features of CVI, AHD, and TVI high-definition technologies based on manufacturer-provided data (see table).
Subjectively evaluating the image, it is worth noting that due to the wide bandwidth, the cameras based on TVI showed the clearest and most saturated picture.
In summary, we can say that the successful history of analog observation is repeating itself, only at the high resolution level. Ahead of the struggle of three almost identical technologies. Which of them will be the most popular - time will tell, but a clear leader has already emerged.
Less than a year has passed since the announcement of the creation of a new video surveillance system, 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 an aspect ratio of 16:9 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 were 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. In fig. 1 shows the general block diagram of the 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, the new format demonstrates significant advantages, and the study of 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. In 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 the old video surveillance system. 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.
In 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 somewhat higher than with a length of 1 m. Even for a cheap Rexant cable, the resolution does not decrease to 800 TVL even 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 principle of pixel-to-pixel transmission and forces us to evaluate the resolution of the HD-CVI system as in 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.
Today I would like to talk about three high-definition video surveillance standards. The developers of all three video surveillance standards pursued the same goals:
- create a video surveillance system that is not inferior in quality to IP video surveillance.
- ensure reliable transmission over long distances.
- provide high resolution
- while minimizing the cost.
In connection with these requests, all three video surveillance standards AHD, CVI, TVI appeared, which made it possible to transmit a video signal in 720p, 1080p and more formats over long distances via coaxial wire without degrading quality.
Now, to replace analog video surveillance, you do not need to drag all the wiring, you just need to replace the cameras and the DVR.
And so let's talk about each format in more detail ...
AHD
The analog high-definition video signal transmission format (Analog High Definition) was developed by the South Korean company Nextchip - this is the most common open format for video surveillance systems. At the moment, there are more than 30 factories in China and Korea that produce and improve this format. High competition among manufacturers leads to a constant reduction in the price of this type of video surveillance cameras and its rapid improvement.
CVI
This format is a development and property of Dahua. The format is one of the world's first high-definition formats, since Dahua is the owner of this format, other video surveillance system manufacturers who want to release the CVI format are required to purchase a license from the manufacturer. Therefore, by default, third-party factories cannot compete with the main manufacturing plant.
TVI
This format was developed by Techpoint. Hikvision is just the main distributor of this video surveillance format.
The format is open, which has recently led to the spread of this format around the world.
Differences in formats in terms of technical characteristics are not fundamental and mainly consist in the cost of building video surveillance systems. The undisputed leader in terms of cost - the most democratic and budgetary, that is, the inexpensive option is the AHD format.
For a detailed comparison of image transmission formats, let's take one of the main characteristics - the image transmission range with the same image quality.
This parameter is one of the main ones, since the key feature of these formats is the increased data transmission range.
Each manufacturer claims that the transmission range of their system is up to 500 meters. At the same time, if you compare tables from different manufacturers, you can see how the parameters of competitors are underestimated.
But practice has shown that all formats at a distance of up to 400 meters show equally well. And if there are differences, they are not noticeable to the naked eye.
But at a distance of more than 400 meters, the difference is already becoming noticeable. If CVI withstands this test without problems, then color can already be lost on the AHD format (it all depends on the quality of the cable), and the TVI format can generally distort and disrupt the picture.
From the above, the following conclusion can be drawn:
Since the image quality on all video surveillance formats does not differ much from each other, and the connectivity and support capabilities, too, it makes sense to focus on the price category. And in the price category, due to the openness and availability of the format, the AHD format is the leader. Therefore, we recommend paying attention to AHD video surveillance systems.
