What is TVI, CVI and SDI?


Industry leaders of standard security camera systems battled for dominance for a time, and not all made it out intact, but the world market has now produced a few excellent video technologies that we'll go over here. These include TVI (Transport Video Interface), CVI (Composite Video Interface), and SDI (Serial Digital Interface), all of which follow under an umbrella called HD-analog. Remember those movies that showed terrible security footage with the fuzzy, unrecognizable perp jumping from frame to frame? That was standard Analog resolution video carried along copper coax cable, and was the most popular style of camera due to the price of a high-end IP camera system that used network CAT5 or CAT6 cable. Thankfully, those days are gone with the advent of HD-analog, as the costs for updating or installing a whole new high-definition camera system have decreased dramatically. 

Industry experts still suggest having a dependable security camera system hard-wired for video and power rather than relying on wireless signal transmission and battery power, unless completely necessary. The risk of data loss is diminished considerably by having an end-to-end connection. While wireless security cameras have become more robust, they can still be affected by harsh weather knocking down an antenna or metal absorbing a signal, like a big box truck getting in between transceivers (queue the suspenseful movie music). A security camera system finds use across various industries, from jewelry stores to hospitals, from sports centers to the local supermarket. We connect with the manufacturers providing security for those sectors so you can have the same peace of mind whether you're putting surveillance around your small business or your property. Products like this 1080p Bullet Camera are good examples of the affordable, high-quality imaging technology that's become standard in the realm of surveillance cameras. 


The answer to the first question is simple: an open market has allowed many variations to flourish, but only a few have become standards across the world. You'll be met with a question in order to answer the second query, which is: what are you trying to do? There is a constant battle in the security camera industry: IP vs. analog. IP cameras use CAT5 or CAT6 cabling, and network video recorders (NVRs) allow for super-high-resolution video recording, but it generally comes at the cost of shorter signal transmission. The maximum distance an IP video signal can travel is generally 325ft without special, same-brand features, which enforce brand loyalty.

Analog-over-coax video resolution cameras, seen in old movies or gas stations, are somehow still holding on. Analog cameras can be mixed and matched, for the most part, and have incredible power to send a video signal nearly 500 meters, almost 5x that of CAT5/6. HD-Analog digital video recorders (DVRs) and cameras have taken the place of standard analog, which includes TVI, CVI, and SDI technologies. These all, essentially, accomplished the same tasks of attaining high-resolution video and sending it over the same coax cable, just in different ways.


Image quality for security cameras was low for a long time. Things like lack of color, lower resolution options, and various other issues of analog systems made it hard to show the value of a camera system to all but those who had the money for it. IP cameras had cornered the market in high-resolution for a long time, even with their higher price points, but innovation won out. Now you can find 4K resolution TVI and CVI style cameras. With crisp, clean video resolutions moving along that legacy coax cable, so many businesses and homes are now able to upgrade or install a new high-definition security camera system at a low cost.


TVI stands for transport video interface. This technology is most commonly seen in security cameras, where a need for high-definition video quality is fierce. Such high-quality footage can be recorded because the data is sent uncompressed through low-cost coaxial cables, making it an industry favorite. Coax cable can transmit the video up to about 1500 feet, often long enough to hook up to a central system that houses all of the data.


CVI stands for composite video interface, and it was the first to crack into the high-definition analog market with its HD 720p line sending video over standard coax cable. This opened the door for so many small businesses to easily upgrade their current, outdated systems. The only pieces needing replacing to receive higher resolution video were the digital video recorder (DVR) and the cameras; the cables did not need to be re-run across buildings, under the ground, or down through the walls!


Analog resolution cameras had the advantage of being interoperable with other analogy systems, as it was a market standard. The people behind TVI and CVI were intense competitors, but it seemed to hurt the industry as a whole to have so many avenues of technology available (analog has never gone away because of the severely lowered costs and interoperability, and SDI was running out of gas by this time) that would not work with each other. TVI was first to reach 1080p, so it quickly overtook CVI, for a time. CVI manufacturers were right behind them, though, and retook some of the market, enough that most security cameras are now created with a switch that enables utilization of either video protocol. This new interoperability allowed the end-consumer to mix and match a system and not punish them for moving from one security camera provider to another. The tech is constantly updating, and both TVI and CVI can now push up to 4K resolution. The transmission of the images is generally good, without much loss of data or footage. If you're looking for a security camera that offers you HD security and great image quality, HD-analog cameras are excellent choices.


Obviously, nighttime image quality is more challenging to achieve than daytime. Transmission interference, power, and other issues are major concerns, and quality is generally lower. Consider, as an example of a great infrared camera, this 1080p Mini Armor Dome Camera, designed for nighttime security. It has an impressive nighttime range of 70 feet with infrared technology. Cameras like these are paired with a DVR via a coax cable to record the footage. This specific camera supports different formats, such as analog, CVI, TVI, and AHD. If you want good nighttime image quality, consider utilizing a product like the one above. It will offer the resolution and support you're looking for without breaking the bank or compromising essential features.


For the most part, there are two ways to go about selecting lens options. Larger lens sizes offer high-quality imaging but tend to suffer from a narrower field of view. The opposite goes for smaller lens sizes: a larger field of view (with which you can spot more general activity), but the available quality and resolution tend to be lower. 2.8, 3.6mm, or 6mm lens sizes are widespread and standard. Many different cameras offer either a fixed lens or what's called a "varifocal" lens that can change the focal length to zoom in or out. A product like this 1080P Mini Armor Dome Fixed Lens Security Camera with IR offers a fixed lens, whereas this 1080P Dome Surveillance Camera with IR & 2.8-12mm Lens has a motorized zoom that can be operated from the DVR or an Android or iOS application. Make sure to choose a product and lens option that suits the level of coverage you need for your security.


SDI stands for Serial Digital Interface. The main difference between SDI and other HD-analog systems is that SDI is an older, more expensive analog technology, made initially in the 90s. Generally, it has more technical limitations than TVI or CVI. TVI is newer, open-source video technology, and many companies have developed their own flavors. CVI is limited to one manufacturer, but it ensures standardization. TVI and CVI, overall, have better support and compatibility with other technologies, and they aren't fussy at all with how you cable it. Both have a longer cable run limit - easily 500 meters for uncompressed data - while SDI's limit is far lower at around 100 meters and reacts far worse to bending and crimping in a coax line.


AHD means Analog High Definition. The normal resolution for this camera type is 720p - a noticeable step downwards from the 1080p offered by the others under the HD-analog umbrella. Transmission range is another issue, only having an effective range of about 150 meters - about 1/3rd of CVI and TVI's 500 meters. For security cameras, these issues can create headaches of not reaching all areas needing coverage and not being able to see details clearly enough.


Security cameras should be wired with the degradation of information in mind. Place and install them in the best possible location to capture the footage that you need, but try to keep the cabling short if possible. Longer runs from the camera to the DVR increase the chance of the signal being degraded as it is transmitted through the coax cabling, whether from crimping the line too much or passing other high-voltage wiring, though the general maximum video transmission distance for CVI or TVI is nearly 1500ft.


You're also going to need a CVI or TVI compatible DVR in order to record the footage. A good example of a great digital video recorder would be something like this 4 Channel 4MP High Definition Hybrid DVR. It supports multiple resolutions, has a huge potential storage size by supporting 8 TB storage, and does everything you'd need it to in order to record footage from CVI or TVI security cameras. In a true spirit of interoperability, it even has two digital channels available for up to two wireless IP cameras to be recorded! This will work as long as they are on the same network as the DVR. When looking at CVI or TVI compatible DVRs, you really want to check the resolutions they support, as well as the size and level of recording they'd be able to handle. You wouldn't want footage being lost because a DVR suddenly became full overnight while you weren't there, after all. With that in mind, make sure to select for storage, resolution, megapixel size, and other important factors.


CVI - Composite Video Interface, created by Dahua
CVI is a licensed video technology that can send 1080p video over coax further than IP cameras can.

TVI - Transport Video Interface, adopted by Hikvision
TVI is an open technology and also can send 1080p video over coax. CVI and TVI both can send video up to about 500 meters.

HD SDI - High Definition Serial Digital Interface, created by SMPTE, The Society of Motion Picture and Television Engineers
SDI is a digital signal carried over coax, just as digital video for IP cameras is carried over cat-5. SDI is much more limited in signal transmission, only going about 100 meters, experiences much more signal data loss with cable bending or crimping, and generally come with higher costs.


They all have in common the ability to transmit 1080p video over coaxial cable, which democratized the CCTV world and allowed smaller firms to become more competitive with established CCTV installation companies. It's begun to raise expectations of what you'll get out of usable video footage from a break-in, a hit and run, and even from seeing a shoplifter. The type of detail available from all technologies is remarkable and has far surpassed traditional analog signals. Since CVI and TVI transmit video in 1080p or 720p analog signals, those technologies have made upgrading from a traditional analog camera system to one capable of HD an easy task. Many CVI DVRs and TVI DVRs can support existing analog cameras, so upgrading the DVR doesn't require you to upgrade your cameras simultaneously. Many HD-analog security cameras now have a switch to go between different HD signals or revert to a lower resolution analog signal, so you can add HD cameras to an existing DVR and upgrade the DVR when you're able.

HD SDI technology has begun to produce hybrid SDI/Analog DVRs. SDI does carry a heavier price tag than CVI and TVI since it is an actual digital signal vs. analog. CVI video is typically better during daylight and can travel up to 500 meters, comparable to TVI, while SDI can go up to 100 meters. As technology advances, CVI and TVI have begun to improve DVR compatibility with IP cameras, allowing consumers to get the highest resolution possible where it matters. While Dahua is the only manufacturer in the world for CVI, Hikvision has embraced TVI, each expanding and enhancing to keep up with the demands of our times.


All of the above except IP is limited to 1080p resolution. Some manufacturers are now producing IP cameras that are capable of capturing video qualities very high above 4K, which may be overkill for a home, but becomes necessary when trying to count cash along with a cashier. It is ideal for jewelry stores, gas stations, college campuses, and anywhere else that high quality and great detail is needed. There is no doubt that CVI, TVI, and SDI have changed the way we see things in the surveillance world, and with how quickly advancements are being made, it's only a matter of time before more improvements hit the market.