What is AHD?

1. Concept
In a general sense, AHD is the abbreviation of American Heritage Dictionary, which is the phonetic symbol of American Traditional Dictionary. This interpretation is used more. From the perspective of security, AHD stands for Analog High Definition.

Analog High Definition means analog high resolution. Regarding High Definition, in simple terms, we usually call the format with a physical resolution of 720p or higher as HD, or HD for short. It refers to the vertical resolution of the screen as 1080i, 720p or 1080p.1080i means that the resolution is 1920×1080, using interlaced scanning, and presents 30 complete pictures per second; 720p means that the resolution is 1280×720, using sequential and progressive scanning, and presenting 60 complete pictures per second; 1080p is Refers to a resolution of 1920×1080, with sequential scanning, presenting 60 complete pictures per second, while AHD is based on the AHD protocol and uses an analog coaxial cable to transmit progressively scanned high-definition video.

2. Transmission distance

AHD is as simple and convenient to operate as traditional equipment. It can transmit up to 500 meters of high-definition lossless transmission with ordinary 75-3 coaxial cable. Delay, high efficiency, anti-interference and easy-to-implement megapixel-level high-definition video transmission.


Third, the scope of application
AHD follows the path and method of analog SD transmission, which can reduce the complexity of construction deployment, reduce the cost of auxiliary materials and maintenance complexity, as well as the technical requirements for construction personnel. It is very suitable for the upgrade and transformation of old systems, and can be used without changing the original Based on the system, it is easy to upgrade from SD to HD. In addition, the price of HD quality and SD gives AHD a lot of room for development in both the civilian and industrial markets.

Four, eight characteristics of AHD products:
①Clearer: advanced bright color separation, signal filtering, 3D noise reduction technology, higher image clarity, better image restoration
②The transmission distance can reach 500 meters with the common 75-3 line of coaxial transmission
③Zero delay: The front-end data is not encoded and compressed to the back-end, full real-time, high-fidelity;
④Good compatibility: compatible with ordinary D1/960H, compatible with analog peripherals (including distributors, matrixes, etc.)
⑤Easy to operate: Support OSD menu design, whatever you want, set what you need ⑥ Low cost: ordinary analog price, high-definition quality products
⑦High integration: AHD front-end chip price, high-definition quality products
⑧Open standards: third-party open standards open
Highlights: high-definition, low-cost, long-distance, no delay, anti-interference, easy to operate.


5. Analog HD market
HDCVI is generally 720P, so HDTVI should go directly to 1080P. It seems that AHD does not have a 1080P version, so its camp is clearer. In the simulation of this almost "dead water" battlefield, No one is willing to make some less competitive products.

The TVI specification is relatively the highest, but its problem lies in the weak transmission performance. When choosing a video amplifier chip, CVI only needs more than 30M chips, and TVI needs 70M. Subject to this specification, TVI The transmission distance is the shortest, and the requirements for the cable are the highest. In fact, in actual applications, it does not matter whether the coaxial HD can reach 500 meters. As far as the current analog high-definition image effect is concerned, it is still 500 meters Image, but the quality cannot be guaranteed. Some engineering companies said that there is no problem with 75-3 cable transmission at 300 meters, and problems such as noise at 400 meters are already more obvious. In fact, from the perspective of engineering wiring, 500 meters is not of much practical value. Because wiring over 300 meters basically uses optical transceivers. Therefore, it can be said that there is not much difference between 500 meters and 400 meters, or the transmission distance is overemphasized for coaxial HD does not make much sense.
A security engineer said that AHD should be the worst in terms of compatibility. "It can''''''''t extend to 1080P upwards, but TVI can. Although CVI has a limited transmission distance, it is at least possible. Next, will the new 1080P specification of CVI There are changes, but it is still unknown. If changes are needed to support 1080P, its compatibility also has some problems."

One more thing to note is that AHD combines the TX chip and ISP. The ISP chip contained in the two-in-one chip is actually more expensive. Some people in the industry said that if the ISP chip in AHD is taken out separately , The corresponding model can be found in the list of chip manufacturers. And the price of a single chip is more expensive than two pieces together, which shows the promotion of AHD by chip manufacturers.