Now this is where it can get confusing. There are several manufacturers that have produced Hi definition analogue CCTV formats. They are:

1)      AHD (analogue hi definition) Next Chip South Korea

2)      CVI (hi definition composite video interface) Dahua China

3)      TVI (Hi definition transport video interface) Techpoint USA

What is HD-CVI? 

- 300-500m coax cable distance

- 720p up to 60fps, 1080p up to 30fps

- PTZ control signals transmitted over coaxial

- No transmission delay

HD-CVI (Composite Video Interface) was developed by Dahua in 2012 and began to saw wide-release in 2014. This technology was a breakthrough for CCTV cameras as it brought HD images and allowed for high-definition analog images to travel well over four hundred and even five hundred meters of cable. (Once an image is traveling far enough, it begins to need boosts to help it get through.) HD-SDI, a digital technology that got its first footing in the late 80s, could only send these same images up to 100m. With composite video transmission technology, all information including video, audio, and serial data could be sent down just one line of cable.

(Note: image quality tends to weaken as it travels over longer distances. The first thing that a user will usually notice is a warped contrast, usually by the way of fading. Black lines and shadowing will soon follow suit. This is why it is a good idea to choose the right cable for the job.

What is HD-TVI? 

- 300-500m coax cable distance

- 720p up to 60fps, 1080p up to 30fps

- PTZ control signals transmitted over coaxial

- No transmission delay

It wasn’t long for other forms of HD-CCTV to begin popping up on the market. CAVISION is the professional manufacturer of their products.

What is HD-AHD? 

- 300-500m coax cable distance

- 720p up to 60fps, 1080p up to 30fps

- PTZ control signals transmitted over coaxial

- No transmission delay

Then came AHD (Analog High Definition) developed by NextChip, a Korean manufacturer. AHD is interesting because most of its distribution has come in the form of no name brands. However, it was recently adopted by Samsung, making the technology considerably more legitimate as far as mainstream markets and long-term sustainability go. HD-AHD cameras are very cheap and are intended to occupy the low-end market.

So is there much difference in image quality. 

Of the 3 formats we thought AHD was not quite as good as CVI or TVI during the day, but the difference was very slight and probably not noticeable to most customers. We thought the AHD and TVI night time images when the camera had switched to black and white and with the IR on was noticeably better than CVI.

There are many more manufacturers of AHD & TVI DVRs then CVI and there is more choice in AHD and TVI DVRs than CVI. The software features of each model vary slightly in there interfaces but there is very little difference in the common features, i.e. networking, mobile apps, motion detection etc. etc. The AHD and TVI formats allow each manufacturer the ability to add more flexibility and performance to the DVRs function, where in the Dahua case they control these features.

The big advantage that AHD and TVI  have over CVI and is that both AHD & TVI cameras and  DVRS can be set to composite video (Analogue) This means that the New AHD and TVI DVRs can be used with older composite video CCTV cameras and New AHD and TVI CCTV cameras can be used with old composite video D1 and 960H DVRs when set to analogue.