Clarifying the myths of HD-Over-Coaxial solutions
Editor / Provider: Alf Chang, a&s International | Updated: 12/15/2014 | Article type: Tech Corner
HD-over-coaxial solutions, which transmit high-definition video over coaxial cables, provide an alternative to HD surveillance besides IP. However, there are still doubts and concerns from the market about how they are set up and whether they can truly deliver. This article lists some of the myths concerning HD-over-coaxial and demystifies them one by one.
Q: For HDCVI, it's compatible only with its own DVRs. What about HDTVI and AHD? Are they able to connect with any type of DVRs?
A: The answer to this is of course negative. Each HD-over-coaxial solution has its own format and must go with its own DVRs. The only solution that's compatible with all formats is 960H. After initial testing, it was confirmed that different-brand HDTVI and AHD cameras can work with their respective DVRs, as long as the same format is used.
Q: Will HDCVI and HDTVI completely replace 960H, since their picture quality is the same as 960H?
A: In terms of what the 720p HD-over-coaxial solution can offer, it is indeed very similar to 960H picture quality. However, 960H products still stand out since they are offered and supported by most of the current camera vendors. We can assume in the future, if there are more 1080p HD-over-coaxial solutions being introduced to the market, it will definitely affect the market of 960H or even IP for the SMB sector.
Q: Could the current HD-over-coaxial DVRs support 720p and 1080p at the same time?
A: The answer is no. Test results show that HDCVI, HDTVI, and AHD each can support 720P and 1080P cameras and corresponding 720P and 1080P DVRs. The issue right now is whether the same DVR can record 720P and 1080P videos at the same time, no matter which technology is employed. This still needs to be confirmed.
Q: When different numbers of HD cameras are used, or when coaxial cables of different lengths or grades are used, would there be any signal loss issues? Experience dictates that when signals are transmitted through different-length coaxial cables, the disparity in voltage may cause poor reflection of images, which may appear to be stacking up on one another. Or, the difference in electrical grounding may create noise. Will this also affect HD-over-coaxial?
A: The answer is yes, due to the lack of equalizers in HD-over-coaxial DVRs at the current stage.
Q: From a project implementation perspective, does transmission distance for HDCVI, HDTVI, and AHD matter? Is it a key factor to consider?
A: Another good question. Each HD-over-coaxial solution claims to be able to transmit over a distance of 300 to 500 meters, or even 600 to 1,000 meters. First, we must applaud HD-over-coaxial for breaking the distance barrier. Yet from a project perspective, this doesn't really mean anything. First, in the past, transmission over a 5C-2V cable without a booster can go for 200 to 225 meters. With booster, transmission can be extended to over 400 meters. Yet quality loss is a byproduct of signal boosting, as noise is augmented. So for any coaxial implementation, shorter distances are preferred due to reliability. To transmit beyond 500 meters without sacrificing picture quality or reducing the number of cameras, what's usually done is the usage of multimode fiber for distances of three to five kilometers or single-mode fiber for longer distances. With a dense wavelength division multiplexing device, one multimode fiber or single-mode fiber can transmit four to 32 streams. In other words, from a project perspective, transmission distance is not an issue and is not a determining factor for choosing between HDCVI, HDTVI, and AHD.
Q: With HDCVI, HDTVI, and AHD breaking traditional distance barriers, can they really help with larger projects, or are they more suitable for SMEs?
A: No matter what grade of coax cable you use, it's just a medium. Transmission distance really depends on the system and voltage. The size of project depends on several things – for example, whether there will be compatible matrix systems like those used for HD-SDI, or HD DVRs that support more channels. Only by then will the discussion of which solution suits which type of project be more meaningful. For now, HD-over-coaxial is implemented in the same way as traditional analog, namely for small- to medium-size projects through a DVR+CMS architecture.
The above were answers to questions commonly asked of HD-over-coaxial solutions. Once they are more widespread in the market, there will surely be more questions concerning their technology and applications. That's when HD-over-coaxial will truly become a game changer.
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