CCTV – HD-TVI or IP – Which to Choose?
We find that most end users aren’t interested in the specifics of a CCTV system. They just want to be able to view and record certain areas. Frame rates, recording quality, compression and recording capacity generally aren’t of interest; just the price. Unfortunately people just don’t find security very interesting..!
For those of you that are interested, here is a simple explanation outlining the key differences between Analogue HD TVI and IP, which are now the two most common technologies in the CCTV world.
HD-TVI stands for High Definition Transport Video Interface. IP stands for Internet Protocol. This, to most of us is actually completely meaningless. What we just need to know is what makes these two technologies different and why you may choose one over the other.
HD-TVI was designed to retrofit to an existing installation where the cameras are already installed on coax cables (up to 500m) or even CAT5. The cameras are very economical in price, costing a similar amount to old technology analogue cameras; ones that are specified in TVL (eg 700TVL). The difference however is that HD-TVI cameras are “High Definition” and use megapixel imagery.
Depending on the model of camera, HD-TVI can provide 2 or 3 megapixel images. 2 megapixels is appropriate for most situations. The biggest benefit of TVI is that you can upgrade your legacy analogue technology cameras with cameras that are comparatively inexpensive whilst saving even more money by not having to re-run expensive cables.
TVI DVR’s (Digital Video Recorders) accept old analogue cameras as well as the new TVI cameras, and most even accept a small quota of IP cameras. This means that you can upgrade your DVR and a select few cameras to High Definition ones, incorporate the existing legacy analogue cameras and only replace them when they start to fail or your budget allows.
IP cameras simply work in a different way than TVI but ultimately provide the same result. IP cameras are usually run on CAT5 cable so if a new building had structured cabling installed to most locations then adding some data points at the positions where you need cameras could be a simple task without running hundreds of metres of new cable. That said, gone are the early days of IP when it was assumed an IT department would share their cables and server space with the CCTV system. Too much bandwidth is taken up and nowadays it is more common for the IP system to have its own dedicated structured cabling back to its own network rack and NVR.
IP cameras can work on legacy coax but you need expensive converters. You’d generally only use such converters if you were updating a large system with new cable and IP cameras, but one or two cameras were quite remote, perhaps run through ducting, and replacing the cable would be very labour intensive and therefore costly. Converters just add a degree of flexibility.
IP cameras can have much higher megapixel capabilities than TVI but this would only be necessary if you are looking to cover a very large area with a single camera, such as a live street scene, large car park, busy concourse etc, where being able to zoom in on features is of paramount importance.
A great benefit of IP is that cameras can be “PoE” – Power over Ethernet. This means that the CAT5 cable that runs from the camera to the NVR (Network Video Recorder) carrying the video picture can also carry the power (normal network distances of 90m generally apply). Cameras are often powered directly from the NVR itself (on systems up to 16 cameras) and where that isn’t possible, from PoE network switches.
TVI cameras are generally 25% cheaper than their IP counterparts. That price is on the equipment alone – so if you don’t need to run new cables (ie in the case of having existing coax cable infrastructure) then often there is no case to justify upgrading to IP.
For small systems of 2-8 cameras being installed from scratch, depending on the actual cameras used the cost between TVI and IP can sometimes be almost comparable. This is because we could potentially use a top of the range TVI camera with a 2.8-11mm lens (adjustable between wide angle and narrow angle) but when it comes to the more expensive corresponding IP camera, we could used a model with a fixed lens of average angle (say 6mm) whose view cannot be adjusted, which will be cheaper. So you’d sacrifice being able to tweak the camera specifically to a view you want to focus on to one that is a fixed general view, which however is often acceptable. So if you were intent on an IP system then this would make it more affordable.
A 2.0megapixel image is approximately 4 times higher quality than a 700TVL conventional analogue camera. Whether this is with a TVI camera or an IP camera will usually come down to whether there is existing cabling, the requirements of the site, the types of cameras required and the budget of the client. Generally, some IP camera model ranges have smarter looking cameras with smaller footprints, but this would not always be noticeable to the untrained eye once they are fitted.
Where IP comes into its own is over large sites where you need more than 16-32 cameras or where the site has satellite buildings which all require cameras. A CAT6 cable can be run from the Comms room or security office to each satellite building in a hub formation where it connects to a network switch, and all the cameras from that building run back to that local switch. With TVI, all cameras would require individual cabling back to the central DVR.
So, in answer to the title of this article, both technologies most definitely have their place. If a company had to focus on just one technology then clearly it would be IP as there are no limitations to the size of system you can achieve. However, to be fair and honest to clients, weighing up their specific needs, it would be unfair to only offer what could turn out to be the most expensive option when a cheaper alternative will provide the same solution.