INSIGHTS
As video surveillance migrates to IP, HDcctv is offering a midway point for users with existing investments. Alf Chang, a&s consultant, discusses the benefits and setbacks of the HDcctv approach.
HDcctv cameras, which we will refer to as HD-SDI cameras for their transmission type, are all the rage in security. Complete product lineups popped up at major trade shows this year, generating global buzz. As part of our camera test, we tested 19 network cameras and six HD-SDI models. With more camera options than ever, we were interested in the performance of HDSDI, combining coaxial transmission with high-definition resolution.
Pros and Cons of HDcctv in Video Surveillance Applications
Date: 2011/07/19
Source: Alf Chang
Real-World Challenges
It seems that HD-SDI cameras are fairly complete as products. However, there are still real-life hurdles to overcome when applying them. The HD-SDI cameras tested had some usage issues, along with problems integrating with peripherals commonly found at installations. While these issues are well-known to manufacturers, users may still be in the dark.
As few users have deployed HD-SDI solutions, we examine some issues that came up in our tests.
Transmission
HD-SDI cameras do not use the same digital encoding signals, which mean they might not be compatible with third-party HD DVRs. While most manufacturers would deny this, our tests proved otherwise. We borrowed multiple HD-SDI DVRs to connect the six HD cameras. All the cameras deployed the standard SDI connector. However, some of the DVRs tested would display error messages after the cameras were plugged in, such as, “This format is not supported.”
Even after switching the display to 720P or 1,080P resolution to make the format the same, we noticed differences in the various versions of SMPTE (292M, 372M and 424M). Each version used different signal bit rates from 1.486 Gbps to 3 Gbps. Some HD-SDI cameras would not display if they changed bit rate. The same 720P image stream would not be recognized by the DVR if it went from 1.486 Gbps to 1.5 Gbps. This is likely a compatibility bug that needs to be taken seriously.
HD-SDI and HDMI
HD cameras using HDMI transmission cabling will have different interference levels, as well as different distances before quality drops. HDMI transmission distance is not limited to just 10 meters, but has yet to reach its theoretical threshold of 20 meters.
Actual tests of HDMI cables will start to suffer image loss at about the 15-meter mark. This is something users and manufacturers should note for its real-world limitations.
Third-Party Support
HD-SDI cameras come with many SDI, HDMI or SDI-DVI converters, along with extension peripherals. However, they will not always work on a third-party HD-SDI camera. This was a documented fact from our camera tests, which is something for manufacturers and users to consider before adopting HD-SDI solutions.
Lack of interoperability for an established broadcast standard was an important finding, as compatibility issues should be relegated to network cameras rather than HD cameras using the same coaxial cabling. HD-SDI camera makers brag about their plug-and- play interoperability, but their claims need to be backed up with proof. Our came rates looked at the advantages and disadvantages of HD-SDI cameras. We hope our findings offer integrators and users more accurate data as a point of reference.
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