ideo signal standard - AHD, HD-TVI, HD-CVI

AHD, HD-CVI, HD-TVI, and CVBS are video signal transmission standards, or technology standards, used for transmitting video signals from surveillance cameras. Hybrid cameras are widely used today, providing compatibility with all these standards.

CVBS in Video Surveillance?

CVBS signal transmission in video surveillance uses RG59, CAT5, and CAT5e. The signal is highly sensitive to cable quality (its shielding) and external factors - it can be affected by electromagnetic interference that occurs when the cable is close to other electrical or electromagnetic sources. There are also significant signal losses when using RG59 cable; the maximum transmission distance is 100m. Nowadays, this distance can be longer, but during the time when CVBS was widely used, 100m was its extreme limit.

CVBS is an analog video signal type that was widely used until the introduction of available high-resolution analog video standards such as AHD, HD-CVI, HD-TVI. Nowadays, it is outdated and no longer widely used. The maximum technical capabilities of the CVBS standard from a modern perspective are relatively modest:
The highest achievable resolution depended on the device and provided 720 x 480 pixels or sometimes 704 x 480 pixels, known as D1. The 4CIF standard was also common. Both of these standards provided an image with an aspect ratio of 4:3.

For widescreen displays and cameras, the resolution standard 960H developed, indicating the horizontal pixel count - 960 x 480 pixels. This provided an image with an aspect ratio of 16:9.

Due to these technically limited capabilities, around 2015, new technological solutions were developed in the video surveillance industry. These solutions allowed the development of closed-circuit surveillance systems based on analog video signal transmission and provided the ability to transmit high-resolution images in digital format using, for example, old coaxial cables used for analog cameras.

What is AHD, HD-CVI, HD-TVI video surveillance?

AHD (Analog High Definition), HD-CVI (High Definition Composite Video Interface), and HD-TVI (High Definition Transport Video Interface) are high-resolution analog video standards developed to provide high-quality video transmission over coaxial and twisted pair cables, such as RG59 and CAT5, CAT5e cables.

All of these are widely used video signal transmission standards today, enabling the transmission of video, audio, and two-way control data, such as PTZ cameras or OSD menus, over long distances up to 8MPx. The technology of these standards continues to evolve, and they are very similar in their technical capabilities. However, each has its unique features and advantages. One common advantage compared to concurrently developed IP camera technology is that all these standards exhibit no noticeable image transmission delay, or latency.

It is important to note that compared to the analog video standard CVBS, all these standards are much more resistant to electromagnetic interference.

HD-CVI is a technology developed and patented by Dahua.

HD-TVI is a technology developed and patented by Hikvision.

AHD is an unpatented, freely available technology.

In our observations, the best image quality is often achieved by using the signal type associated with the manufacturer. For example, when connecting a camera to a Dahua recorder, even a hybrid one that allows choosing the video transmission standard, a better image is obtained by using the HD-CVI signal transmission standard.