High Definition Analog Video Surveillance 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 monitors and televisions have long overcome the "bar" of Full HD, looking at them from cameras that issue a resolution of D1 (704x576) or even 960H (960x576) is just bad news. Therefore, equipment manufacturers promptly fussed and offered users three high-definition analog video surveillance standards at once: HDCVI, HDTVI and AHD.
    The analog remains in service.

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

    HDCVI

    Dahua Technology was the first to enter the high-definition analog video market with its HDCVI (High Definition Coaxial Video Interface) technology. This is a proprietary technology that other manufacturers must purchase a license for.
    The HDCVI standard provides signal transmission using quadrature amplitude modulation technology, completely separating luminance and color signals. You can get acquainted with the equipment here: Dahua


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

    The separation of luminance and color signals can significantly eliminate the cross-distortion of composite video signals characteristic of conventional analog CCTV (closed circuit television) cameras, which improves image quality. Additionally, HDCVI uses the automatic signal correction function, which reduces the distortion of the original video signal when transmitting over long distances.

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


    Fig. 2. The modern analog HD video surveillance system uses the traditional star topology.

    At the same time, HDCVI is capable of transmitting at once three types of signal in one cable: a video signal, an audio signal, and control commands for PTZ PTZ cameras (focus, tilt, pan, zoom, transmit an alarm, etc.). This technical solution greatly simplifies cabling. Analog surveillance systems of previous generations could not boast of anything like this and required the laying of additional wires for transmitting audio and control signals.


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

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

    HDTVI

    The manufacturer did not reinvent the wheel - like a competitor, the standard involves the separation of the luminance signal and color signals, and the algorithm for preliminary processing of the unmodulated video signal with the subsequent application of quadrature amplitude modulation helps to avoid interference and get a clearer image. At the same time, of course, this algorithm is proprietary (that is, a unique development of the company), and does not fall under Dahua's patents. Due to the use of relatively low-frequency modulation, the HDTVI standard, as well as other analog HD systems, is not very demanding on 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 transmission range of the video signal is announced up to 500 meters when using high-quality coaxial cable, while digital solutions are limited to a distance of 100 meters over a twisted pair cable. You can view cameras and recorders here:http://yumtrade.ru/200814-hd-tvi-videonabljudenie
    Automatic signal compensation (option AGC, 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/ ), of the three competing systems, the HDTVI system is the least resistant to signal distortion when working on a long combo cable (coaxial + power). Apparently this is a drawback of the “proprietary” signal compensation algorithm.
    HDTVI provides two-way control signal transmission to / from PTZ cameras on a single cable simultaneously with video transmission. Further development of the standard also promises the transmission of audio signals on the same wire.


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

    We 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 for which is implemented at the hardware level. But at the same time, HDTVI technology can very specifically support conventional analog cameras, high-definition cameras and IP cameras. To achieve hybridity (the ability to connect different cameras, including digital IP), the HDTVI solution requires an additional hardware analog video decoder, which significantly increases the cost of the system. Or only one IP camera is supported, the image quality of which is also “cropped” additionally. 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, the "open" HDTVI equipment is somewhat more expensive than the similar in capabilities of the "open" AHD. This is probably why HDTVI is still inferior to AHD in popularity.

    Ahd

    AHD (Analog High Definition) technology was developed by Nextchip, a well-known manufacturer of video chip devices. Like HDTVI, AHD technology is absolutely open to all manufacturers: any manufacturer who expresses a desire can produce AHD equipment. But compared to HDTVI, the AHD option has the important advantage that all AHD video recorders are able to work 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 such a "symbiosis" is not excluded at many sites), then this will be exactly the AHD technique. Access to the Internet 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. Get acquainted with AHD equipment:http://secur.ua/videonablyudenie/analoghd/


    Fig. 5 . AHD technology initially supports multi-hybrid mode: AHD DVRs are capable of working with analog, AHD and IP cameras simultaneously.

    AHD technology can even completely replace IP solutions, offering a lower price and ease of installation with a picture quality level not inferior to digital. Using AHD, it is also easy to ensure a smooth transition of a video surveillance system from analog to promising IP. After all, as with digital systems, the AHD video signal is successfully transmitted through a twisted pair cable, and not just through coaxial. As for signal transmission at AHD, the 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 color, plus it is protected by noise reduction algorithms.
    AHD cameras can be both the simplest and the most advanced, containing their own settings and OSD menus. In these cameras, basic analytics functions are implemented: motion detection, tracking camera closure, signal loss, it is possible to add private zones protected from viewing, etc. With the help of additional software and thanks to the high resolution of 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 is claimed for all high-definition video technologies, FullHD cameras and recorders are still available only on the basis of HDTVI and HDСVI 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. We will highlight key general points:

    • the usual star-shaped topology and work with existing cable systems simplify the installation and configuration procedure;
    • the use of progressive scan and high resolution 720p and 1080p for video, which has the most positive effect on image quality and detail;
    • improved noise immunity due to the use of separate luminance and color signals, the use of similar algorithms for eliminating interference and signal correction;
    • relatively low requirements for cable characteristics, quality of manufacture and installation of connectors;
    • the possibility of using both coaxial cable and twisted pair cable for signal transmission;
    • video transmission over coaxial cable over considerable distances without loss of quality;
    • there are no losses and frame delays, as in digital solutions.

    The technology differences are as follows:

    • HDCVI is the only one of three proprietary technology that is exclusively owned by 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 royalties;
    • HDTVI is an open technology, but with limited compatibility of equipment in hybrid mode and worse resistance to interference when the cameras work at a great distance from the recorder;
    • AHD offers, in addition to the complete openness of technology for manufacturers, a rather humane pricing policy for equipment and an excellent implementation of multi-hybrid technology, when even the most inexpensive DVRs can work directly with three types of cameras - standard analog, AHD and IP.

    The table below shows 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


    Coaxial cable transmission range, m


    300


    500


    500


    500


    impossible


    Signal transmission range over twisted pair UTP CAT.5e, m


    100


    150


    100


    150


    100


    Possibility of simultaneous connection of analog, HD and IP cameras


    not


    Yes


    not


    Yes


    not


    Having image delay and frame loss problems


    not


    not


    not


    not


    Yes


    Control signal transmission via video cable


    not


    Yes


    Yes


    Yes


    Yes


    Audio transmission via video cable


    not


    Yes


    not**


    Yes


    Yes


    Compatible with devices from different manufacturers


    Yes


    not


    Yes


    Yes


    Yes




    * - will appear in the near future



    ** - expected in the future



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

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