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What's the difference between Cvi and analog? HD-TVI is a new video surveillance format. Level of compatibility with legacy infrastructure

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 as much as possible.

In connection with these requests, all three video surveillance standards AHD, CVI, TVI appeared, which made it possible to transmit video signals in 720p, 1080p and more formats over long distances over coaxial wire without degrading quality.

Now, to replace analog video surveillance, you do not need to re-tighten all the wiring; you only need to replace the cameras and the video recorder.

So let's talk about each format in more detail...

AHD

The high definition analog 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 developed and owned by 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 produce 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

The developer of this format is 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.

The differences between the formats in terms of technical characteristics are not fundamental and mainly lie in the cost of building video surveillance systems. The undisputed leader in cost - the most affordable and budget-friendly, 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 range of image transmission with unchanged picture quality.

This parameter is one of the main ones, since the key feature of these formats is the increased data transmission range.

Each manufacturer assures that the transmission range of their system reaches 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 show equally well at a distance of up to 400 meters. And if there are differences, they are not noticeable to the naked eye.

But at a distance of more than 400 meters the difference already becomes noticeable. If CVI passes this test without problems, then on the AHD format color may already be lost (it all depends on the quality of the cable), and the TVI format may generally distort and disrupt the picture.

From all of the above we can draw the following conclusion:

Since the image quality on all video surveillance formats is not very different from each other, and neither are the connection and support capabilities, it makes sense to focus on the price category. And in the price category, due to the openness and accessibility of the format, the leader is the AHD format. Therefore, we recommend that you pay attention to AHD video surveillance systems.

HD-TVI is a new standard for analogue video surveillance, which allows you to transmit a video signal with a resolution of 1280x720 or 1920x1080 pixels. The developer and owner of the rights to HD-TVI is Techpoint, a widely used trademark Hikvision, from domestic ones - RVI, Space Tehnology, LTV and others. The main difference of the standard is the modified technology for generating and transmitting the video signal: the standard assumes complete separation of the luminance signal and color signals, which avoids the accumulation of interference to obtain a clearer image. In HD-TVI cameras an algorithm has also been implemented for pre-processing an unmodulated video signal with subsequent use of quadrature amplitude modulation for transmission over a communication line - a conventional coaxial cable with a characteristic impedance of 75 Ohms. The cable transmits video and control signals; Unlike its opponents, Techpoint has not yet equipped the HD-TVI format with the ability to transmit audio, but, according to experts, audio transmission over the same cable with a video signal will soon be available. HD-TVI is an open format, that is, HD-TVI equipment can be produced by any company.

For HD-TVI 720p video transmission up to 500 meters, RG-6, RK-75-4 or RG-59 cables are recommended; for HD-TVI 1080p transmission you will need the same cables no more than 300 meters in length. For coaxial cables RK-75-2 or RK-75-3, recommendations are no more than 100 and 200 meters, respectively.

HD-TVI cameras.

HDTVI security cameras offer maximum image detail and improved color quality thanks to the highest bandwidth of all three new HD technologies - up to 55 MHz. Moreover, the signal has higher noise immunity compared to a conventional analog signal.

A feature of the HD-TVI standard is the use of low-frequency modulation, in contrast to the digital HD-SDI standard, which makes it less demanding on the precision of connectors and cable characteristics, and is also less susceptible to high-frequency interference from surrounding equipment. The maximum transmission range of a video signal on a high-quality coaxial cable can reach 500 meters. It is possible to use twisted pair transceivers to increase the transmission distance.

The use of automatic signal compensation technology allows us to minimize distortion on relatively long sections of routes. When assessing the image visually, it must be admitted that, thanks to the wide bandwidth, the most clear and rich picture was shown by cameras built on the basis of HD-TVI. Transmission bandwidth HD-TVI 55 MHz, HD-CVI 40 MHz, AHD (720p) - 12 MHz.

Will the HD-TVI video surveillance standard become popular?

At the moment, the developers of the standard have opened access to the technology to third-party developers, which is logical when competing AHD and HD-CVI standards - Dahua and NextChip - have already done this. The number of developers supporting the HD-TVI standard is still smaller than that of AHD NextChip and Dahua. In the technological race HD-TVI format is considered the most redundant in production, which affects the cost. But he was the next to introduce serial equipment with 1080p resolution after Dahua, while AHD began deliveries to Russia only in the second half of 2015. Technologically for compatibility with the old analog signal in

Recently in systems video surveillance, three new data transmission formats have appeared. Certainly, We mean HDCVI, HDTVI and AHD.

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All three standards were developed independently of each other, but the ultimate goal was the same identical. Create analogue high-definition video surveillance, create real competition for IP video surveillance. What actually happened is just look at the description of the formats: “The HD-CVI/HD-TVI/AHD format (underline as appropriate) provides reliable transmission of a high-definition analog video signal over long distances via coaxial cable” 1 . And now the fairy tale has become reality. Nowadays, users of analog video surveillance systems can improve their system and have high definition resolutions comparable to 720p or 1080p by updating only the end devices and without changing the cabling structure. So - comparison of HD-CVI, HD-TVI, AHD formats

Transmission range

Signal transmission range is one of the key advantages of the new standards compared to conventional analogue PAL/NTSC CCTV. When describing their own technology, each manufacturer uses the following value: the guaranteed signal transmission range when using RG-59 cable is 500 meters. However, none of the developers are as supportive of their competitors. For example, in the comparison table from Dahua, the developer of the HD-CVI format, the transmission range for TVI and AHD is “only” 300 m. The creators of AHD, NextChip, share a similar opinion: in their evaluation chart (see table) they were awarded 300 meters TVI from Hikvision, themselves and Dahua were shown a convincing 500 meters.

In practice, all three standards reliably transmit images without any significant loss in quality over RG-59 cable. Here it is worth paying attention to the wording “no losses”. Like any analog signal, new formats have inherent losses as the transmission distance increases. First of all, this concerns signal resolution and its color. However, on a monitor it is almost impossible to visually determine the difference between images transmitted via RG-59.

The losses were more significant when transmitting a signal over 400 meters using an RG-58 cable. It is this kind of cable that is used in combination cables, which are popular in Russia, combining a coaxial cable for the signal and two wires for powering the camera. HD-CVI survived the experiment, but the loss in resolution and noise in the frame were noticeable. The AHD signal lost color - the output was a black and white image. The HD-TVI signal suffered the most serious distortion, signal reception was extremely unstable, and the picture was periodically lost.

Three in one

Another advantage of the new generation analog formats is the ability to transmit video and audio signals over one coaxial cable, as well as two-way data transmission (RS-485). Moreover, this opportunity is declared in all three formats - AHD, HD-TVI, HD-CVI. But so far this feature is only an announcement; there is not a single device on the market with the indicated functionality. The developers of Dahua have gone the furthest so far, demonstrating HD-CVI video cameras and video recorders with image and sound transmission over a single coaxial cable. And the integration of the RS-485 interface is only a matter of time.

Hybridity

The next important factor when comparing formats is the characteristic of compatibility with the traditional analogue. And here the manufacturers simultaneously announce this possibility. In the case of AHD and HD-CVI, the hybridity of recorders is provided at the level of the receiving chip (RX), which supports both the CVBS format and AHD1.0 or HD-CVI at the input. To implement hybridity, HD-TVI uses an additional analog video decoder. For the manufacturing plant, this means the need to use additional strapping and components. For the end user, by and large, the number of components used inside the device does not matter. Therefore, at this point in our comparison of new formats we put an equal sign.

Resolution

The specifications for all formats include a maximum video resolution equivalent to 1080p. Since the formats are analog, it is not entirely correct to measure the resolution of devices in pixels. In this connection, the word “equivalent” is applicable. Two-megapixel cameras and HD-CVI and HD-TVI recorders are already in mass production. AHD lags behind in this matter by at least 2 months - the start of mass production of equipment in the AHD2.0 format was scheduled for December 2014, but it is not yet on the market. But despite this, the three manufacturers almost simultaneously announced plans to develop systems with a resolution above 1080p . Hikvision announced the availability of HD-TVI systems with a resolution of 3 megapixels (2048x1536) already in the second half of 2015. Dahua, Hikvision, and NextChip announced their intention to develop analog video surveillance systems in 4K format by the end of 2015.

System cost

One of the few factors that differentiates the three formats from each other is the cost of the solution. At the moment, the AHD format video surveillance system seems to be the most budget-friendly - its cost is already comparable to traditional analog CCTV systems. The HD-CVI system is slightly more expensive - on average 10–15% higher than the cost of AHD systems. The most expensive solution is HD-TVI systems; the difference between HD-TVI and AHD systems is 15–20%.

All equipment can already be purchased from our

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Price policy

A key feature in the development of formats may be pricing. Of all the new analogue video surveillance standards listed, the most open is the AHD format, the developer of which, NextChip, specializes in the production and sale of microelectronic chips and components. At the moment, there are already more than 30 factories on the Chinese and Korean markets that develop AHD format solutions independently of each other. As a result of strong competition, new technologies are being refined at an accelerated pace, and prices for solutions are rapidly falling.

Despite the fact that Dahua also sells CVI chipsets, pricing for HD-CVI systems is controlled directly by the plant itself, since the company's main product is primarily ready-made solutions (boards and modules, cameras and recorders).

HD-TVI technology is also open, but its development is highly dependent on investments from Hikvision, and the excessive high cost of the technology has not gained a large number of followers.

Thus, the new analogue video surveillance formats AHD, HD-TVI and HD-CVI are almost identical from the point of view of end consumers. However, the maximum openness of the AHD format for manufacturers of video cameras and video recorders can be the main advantage for the further expansion of this standard in the modern video surveillance market.

Based on materials from an article by Sergei Minevich
1 The source used was: for HD-CVI – the HD-CVI Product Catalog 2014 version 3 brochure, for HD-TVI – the TURBO HD Analog Solution brochure, for AHD – a presentation by NextChip.

Your name HD-CVI format Analog video signal transmission was achieved thanks to direct transmission technology and quadrature amplitude modulation, the use of which avoids cross-distortion of the CVBS composite video signal. At the same time, the brightness and color signals are completely separated, maintaining video quality during transmission. The technology belongs to Dahua.

HD-CVI includes a set of chips: transmitting - TX and receiving chip RX, 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 over a distance of 300 meters for cable RK-75-3 or 400 meters for RK-75-5, and the signal 720P (1280 ×720) over a distance of 500 meters using cable RK-75-3 or up to 650 meters using RK-75-5.

For building CCTV systems HD-CVI cameras and HDCVI digital video recorders are used using the high-resolution 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 a coaxial cable. HD-CVI technology supports two high definition video formats: 1080p (1920 ×1080) and 720p (1280 ×720). The technology is equipped with an automatic signal correction function (ASC), which practically does not allow signal distortion when transmitted over long distances.

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 of which the megapixel video image from HD-CVI cameras Dahua surveillance is transmitted to the DVR with zero latency.

Signal in HD-CVI video surveillance systems transmitted at frequencies below 50 MHz and is much more resistant to interference than when 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 carry multiple signals over a single cable, audio and two-way data signals are placed in a signal attenuation zone. Thus, synchronization with the video signal is enhanced, and thanks to automatic signal correction, a maximum sampling rate of 44.1 kHz is maintained.

Comparison of HD-CVI and IP cameras

Advantages.

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 over 500 meters without using additional. devices via coaxial cable or network cable.

IP cameras require specific (Not low) network bandwidth and there may be delays and losses in the video stream, as well as conflicts with other IP equipment. HD-CVI cameras have no 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 network cable or fiber optics.

Flaws.

IP cameras are capable of higher resolutions than 1080p and available resolutions will continue to grow in the future.

IP cameras are able to receive power via 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

HD-SDI networks are 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 coding method, separating luminance and color signals in a special way.

HDCVI technology equipment significantly cheaper than HD-SDI.

19.02.2018

CCTV: what is it?

CCTV is video surveillance, that is, the process of continuous visual monitoring using optical-electronic devices.

How are analog cameras different from digital ones?

The fundamental difference is not in the quality of the image (with the same optics and matrix), but in the method of signal transmission. Digital IP cameras have a special device that converts an analog video signal into a digital one, as well as the ability to connect to the Internet. The advantage of IP cameras is the absence of losses, the disadvantage is the limitation of the maximum cable length (up to 90m).

The disadvantage of analog cameras is strong losses in signal quality, noise and distortion. The degree of interference directly depends on the length of the cable. The advantage is that the maximum cable length can be up to 1200 m.

HD-SDI: Not an analogue standard

The HD-SDI standard is an attempt to use existing analogue video surveillance lines to transmit a high-quality digital signal; modern coaxial cable is used for such purposes.

This standard has a huge advantage over IP cameras, since it eliminates delays associated with the time spent processing the received information in the camera itself. This is especially true when using PTZ cameras, where a delay of even 1-2 seconds can be quite critical.

Standards: AHD, TVI, CVI, HD-SDI, IP - how do they differ from analog video surveillance?

HD-SDI is a way to upgrade an existing analog system to bring image quality to HD. Moreover, the desired result can be achieved without replacing the existing cable and equipment. But, at the same time, the standard has quite high requirements for the cable itself, as well as connections and connectors.

AHD, TVI, CVI are standards that are incompatible not only with each other, but also with analog television. They are much more demanding on the quality of cable and equipment. In fact, this is a new round of technology development. At the same time, a high-resolution signal is transmitted over a distance of up to 500 m not only without distortion, but also without delays (like IP).

Differences from IP

The use of AHD, TVI, CVI standards in combination with appropriate equipment allows you to output both HD and analog video signals. But it’s worth considering that such systems are more expensive than IP video surveillance, let alone classic analogue ones.