High Definition Analog CCTV Systems: HDCVI, HDTVI and AHD

Analog video surveillance today is moving from standard to high resolution. After all, you need to keep up with the times! When the monitors and televisions have long overcome the "bar" of Full HD, look at them the image from the cameras issuing a resolution of D1 (704x576) or even 960H (960x576) is simply a move. Therefore, equipment manufacturers promptly advised and offered users three standard high definition analog video surveillance: HDCVI, HDTVI and AHD.
Analogue remains in service.

It would seem that if there is a transition to digital formats everywhere, is analog video surveillance itself necessary? Need to. Also how. The fact is that in the world hundreds of millions (!) Of analogue surveillance systems with coaxial cable-based infrastructure have already been deployed. Digital cameras, the same Foscam , cannot work with this cable infrastructure. But the new analog HD cameras make it easy to upgrade all these old systems to the modern level. Avoiding the enormous cost of replacing already wired wires for a twisted pair cable needed for digital cameras. In addition, over digital solutions, analog systems retain certain important advantages, which we will discuss below.
All new analog standards of high-definition video include an aspect ratio of 16: 9 and standard definition HD 720p (1280x720) and Full HD 1080p (1920x1080). In terms of detail, the image format HD 720p exceeds the usual analog format D1 2.3 times, and Full HD exceeds it more than 5 (!) Times. It is obvious that the game worth the candle. New technologies make it possible to consider even at a fairly long distance the details and nuances to which the old analog CCTV cameras passed: features of people’s faces, car numbers, denominations of banknotes, etc. For the successful development of the market, it is also important that the prices for new high-definition analog equipment do not exceed the cost of the old analog technology, or even are on the same level.
Of course, initially attempts were made to monopolize the market of high-definition analog systems, to become a “patent troll” and to profit from the “peace on” principle. However, in the era of active development of open standards, it is becoming more and more difficult, and alternative and open solutions have appeared on the market. Actually, let's compare the competing technologies.

HDCVI
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Dahua Technology with HDCVI (High Definition Coaxial Video Interface) was the first to enter the high-resolution analog video market. This is a patented technology for which other manufacturers must acquire a license.
The HDCVI standard provides signal transmission using quadrature amplitude modulation technology, fully separating the luminance and chrominance signals. Equipment can be found here: Dahua


Fig. 1. Quadrature amplitude modulation technology used in signal transmission in modern analog HD video surveillance systems

Separating the luminance and chrominance signals makes it possible to substantially eliminate the cross-sectional distortion of the composite video signal, typical of conventional analogue CCTV (Closed Circuit Television) cameras, which improves the image quality. Additionally, HDCVI uses an automatic signal correction function, which reduces distortion of the original video signal during transmission over a long distance.

The HDCVI video surveillance system has a star topology, traditional for analog systems, when the central node - the video recorder is connected by a point-to-point (P2P) signal transmission with cameras connected via coaxial cable.


Fig. 2. A modern analog HD video surveillance system uses the traditional “star” topology.

At the same time, HDCVI is able to transmit three types of signal in one cable at once: video signal, audio signal and control commands for PTZ cameras (focus, tilt, rotate, zoom, send an alarm signal, etc.). This technical solution significantly simplifies cabling. Analogue video surveillance systems of previous generations couldn’t boast anything of the kind and required the installation of additional wires to transmit audio and control signals.


Fig. 3. HDCVI technology (as well as AHD) is capable of transmitting three types of signal in one cable at once - video signal, audio signal and control commands.

HDCVI technology will allow you to transmit a video signal over a coaxial cable over a distance of 500 meters or even more if you use a quality cable 75-5 or better.
Fortunately, Dahua’s monopoly loneliness in the market did not last long. So, the company Hikvision presented its own competing development HDTVI (High Definition Transport Video Interface).

HDTVI

The manufacturer did not reinvent the wheel - like the competitor, the standard assumes separation of the brightness signal and color signals, and the algorithm for pre-processing the unmodulated video signal with subsequent quadrature amplitude modulation helps to get a clearer image. In this case, of course, this algorithm is proprietary (that is, the unique development of the company), and Dahua patents are not covered. Due to the use of relatively low-frequency modulation standard HDTVI, as well as other analogue HD systems, is not too picky about the quality of manufacture and installation of connectors, cable characteristics. This is their fundamental difference and at the same time an advantage over digital competitors. Plus, the maximum video transmission distance is claimed up to 500 meters using high quality coaxial cable, while digital solutions are limited to a distance of 100 meters over a twisted pair. View cameras and recorders at the link: http://yumtrade.ru/200814-hd-tvi-videonabljudenie
Automatic signal compensation (an AGC option, or automatic gain control) is also used and makes it possible to minimize distortion and signal loss in long cable segments. However, according to independent tests ( http://sec-invest.ru/articles2/videonabl/sovremennye-formaty-analogovogo-videonablyudeniya-hd-cvi--hd-tvi-i-ahd-v-sravnenii/ ), out of three competing systems it is the HDTVI system that is least resistant to signal distortion when working on a long combined cable (coaxial + power). Apparently this is a drawback of the “proprietary” signal compensation algorithm.
HDTVI provides for two-way transmission of control signals to / from PTZ cameras over a single cable simultaneously with video transmission. Further development of the standard also promises the transmission of audio signals over the same wire.


Fig. 4. Although the HDTVI standard is open, on the equipment side, it is still actively supported by the standard developer, Hikvision

You can add that HDTVI equipment allows you to automatically connect not only HDTVI cameras, but also ordinary analog cameras to the video surveillance system. Support which is implemented at the hardware level. But at the same time to support conventional analog cameras, high-definition cameras and IP cameras, HDTVI technology is able to be very specific. To achieve hybridity (the ability to connect different cameras, including digital IP), the HDTVI solution requires an additional hardware analog video decoder, which appreciably increases the cost of the system. Or only one IP camera is supported, the image quality of which is also additionally “cropped”. We can safely say that IP support in the case of HDTVI is expensive, while both competitors initially and completely free of charge have this important advantage. Thus, “open” HDTVI equipment costs a little more than the similarly “open” AHD. Apparently, therefore, HDTVI is still inferior to AHD in popularity.

Ahd

AHD (Analog High Definition) technology was developed by the famous chip manufacturer for video equipment - Nextchip. Like HDTVI, AHD technology is completely open to all manufacturers: any manufacturer who has expressed the desire can produce AHD equipment. But compared to HDTVI, the AHD version has the important advantage that all AHD DVRs are capable of operating according to a multi-hybrid scheme, that is, with three types of video cameras at the same time — analog, AHD and IP cameras — and without any additional modifications, optimizations and software / hardware shamanism. . Analog, AHD and IP equipment can be easily combined into a single video system and serviced by a single DVR. Thus, if you look for the most affordable equipment with support for analog and digital video surveillance at the same time (and this “symbiosis” is not excluded at many sites), then this will be the AHD technique. Internet access and convenient work through cloud services make working with AHD-recorders even more comfortable for the user, because it becomes possible to control the video surveillance system from anywhere in the world where there is Internet access. See the AHD equipment: http://secur.ua/videonablyudenie/analoghd/


Fig. 5 AHD technology initially supports multi-hybrid mode: AHD video recorders are able to work with analog, AHD and IP cameras simultaneously.

AHD technology can even completely replace IP solutions, offering a lower price and simplicity of installation at the level of image quality not inferior to digital. With the help of AHD, it is also easy to ensure a smooth transition of a video surveillance system from analogue to advanced IP. Indeed, as with digital systems, the AHD video signal is successfully transmitted over a twisted pair cable, and not just coaxial. As for the AHD signal transmission, video, audio and control signals are also capable of being transmitted over a single cable, and the video signal is split separately for brightness and chroma plus protected by interference suppression algorithms.
AHD cameras can be both the simplest and advanced, containing their own settings and OSD menus. In such cameras, the functions of basic analytics are implemented: motion detection, tracking of camera closure, signal loss, the addition of protected from viewing private zones, etc. With the help of additional software and due to the high resolution of the cameras, it is possible to realize much more advanced functions of security systems - for example, recognition of faces, car numbers, bills, etc.
At the same time, although support for HD 720p and FullHD 1080p resolutions has been announced for all high definition video technologies, FullHD cameras and recorders are currently only available on the basis of HDTVI and HDCVI technologies. AHD equipment with FullHD support is expected in the near future.

General and differences

As you can see, the three technologies HDCVI, HDTVI and AHD have a lot in common. Highlight key common points:

• The usual star topology and work with existing cable systems simplifies installation and configuration;
• use of progressive scan and high resolution of 720p and 1080p for video, which has a very positive effect on the quality and detail of the image;
• improved noise immunity due to the use of separate luminance and chrominance signals, the use of similar interference cancellation and signal correction algorithms;
• relatively low requirements for cable performance, quality of manufacture and installation of connectors;
• the ability to use both coaxial cable and twisted pair for signal transmission;
• video transmission over coaxial cable over long distances without loss of quality;
• there are no losses and delays of frames, like digital solutions.

The differences in technology are as follows:

• HDCVI is the only of the three closed technologies, the rights to which belong exclusively to Dahua. Therefore, HDCVI equipment cannot be manufactured by another manufacturer without licensing from Dahua. This significantly limits the market for compatible devices and increases the cost of the final product due to license fees;
• HDTVI is an open technology, but with limited compatibility of equipment in a hybrid mode and worse resistance to interference when cameras are operated far away from the recorder;
• AHD offers, in addition to the full openness of technology for manufacturers, a fairly humane pricing policy for equipment and excellent implementation of multi-hybridity, when even the most inexpensive DVRs are able to work with three types of video cameras - standard analog, AHD and IP.

The table below provides more detailed comparative characteristics of analog CCTV, HDCVI, HDTVI and AHD systems, as well as digital IP solutions.

Table. Comparative characteristics of CCTV, HDCVI, HDTVI, AHD and IP video surveillance systems.

Characteristic	CCTV	HDCVI	HDTVI	Ahd	IP
Camera resolution	960x576, 704x576	1920x1080, 1280x720	1920x1080, 1280x720	1920x1080 *, 1280x720	Up to 4K
Signal transmission distance via coaxial cable, m	300	500	500	500	is impossible
Signal transmission distance over twisted pair UTP CAT.5e, m	100	150	100	150	100
The ability to simultaneously connect analog, HD and IP cameras	not	Yes	not	Yes	not
Having image delay and frame dropping problems	not	not	not	not	Yes
Transmission of the control signal through the video cable	not	Yes	Yes	Yes	Yes
Audio transmission over the video cable	not	Yes	not**	Yes	Yes
Compatibility with devices from different manufacturers	Yes	not	Yes	Yes	Yes

* - will appear in the near future

** - expected in perspective

Total
Modern HDCVI, HDTVI and AHD analog video surveillance systems are far superior to the previous generation systems, which makes the modernization of video systems more than justified. Moreover, the new high-definition analog equipment is already massively available at very attractive prices.