HD-SDI(1): Another option for HD video surveillance
Editor / Provider: Alf Chang | Updated: 12/3/2013 | Article type: Hot Topics
Megapixel cameras and IP-based networks were the only means to get HD surveillance footage. However, analog-related innovations continue to take place. With characteristics similar to analog CCTV, HD-SDI/3G-SDI provides an alternative to IP-based video surveillance.
What is HD-SDI?
HD stands for High Definition, and SDI stands for Serial Digital Interface, a family of video interfaces standardized by SMPTE (The Society of Motion Picture and Television Engineers). HD-SDI and 3G-SDI are related interfaces offering nominal data rates of 1.485 Gbit/s (dual link) and 2.970 Gbit/s serial link, respectively. These two are major interfaces applied for security.
Founded in 2009, the HDcctv Alliance is a non-profit industry association that develops, manages, and promulgates the technical interface specification for HD surveillance. A great numbers of its members are manufactures offering solutions including cameras, sensors, chips, DVRs, converters, extenders, distributors, monitors, and more, which indicate the maturity of HD-SDI maturity.
Roughly 20 Korean manufacturers, 10 Taiwanese brands, and over 40 Chinese companies continue R&D efforts in SDI. The number increases while the alliance continues to evolve and releasing subsequent versions.
HD-SDI reference designs are available from Altera, Ambarella, Hisilicon Technologies, Texas Instruments and Xilinx, making overall solutions more price-competitive. Increasing availability of ISPs also means that integrators and installers may need to pay more attention to different combinations and developments of sensors, FPGAs, fps, and reference designs such as ASIC or FPGA.
HD-SDI takes larger amount of storage capacity than IP
Chipmakers have developed SoCs that help DVRs to compress the video and store it as efficiently as IP-based systems do.
SD Lens on HD camera looks sharp
Neither cameras nor Lenses are created equal, be sure to select the most suitable megapixel lenses for HD-SDI cameras to achieve the required resolution as SD lenses will not work correctly on HD cameras.
Short transmission distance
Improvements in chip technology and the debut of fiber link breaks HD-SDI away from the chains of coax. Besides increasing bit rates, chips also use lossless compression to extend the distance to 300 m. However, the most common practice is to use fiber optic transceivers, which can use WDM/DWDM/CWDM to utilize different wavelengths of light to extend HD-SDI's reach to 30 km to 70 km, up from the paltry 100 m.
Video Management a Problem
HD-SDI lacked a unified platform for video management. However, it is possible to run the video through an SDI server to convert the signals to IP. The data can then be managed by any NVR or VMS. In addition, the DVR can output the video through its network interface into the VMS.
There were no provisions in the standard for camera control so the user could not change the camera settings or send power over it. A separate connector is no longer needed for camera control. With the latest version, HDcctv 2.0 enables multi-vendor interoperability for up-the-cable remote control, bi-directional metadata, and optional audio. The bi-direction communications protocol is simple, wherein paired ports exchange 255-byte packets patterned on the PSIA and Pelco-D protocols. Also, the power-over-coaxial feature allows power through coaxial cable from DVR to camera while no additional power supply is required.
Specialized Displays (Confirmed)
For the most part, current video surveillance displays use CVBS and VGA interface. When it comes to high definition video, two prominent formats are 720p and 1,080p. The HDTV SMPTE-296M/274M requires that the interface were HDMI or DVI and YC.
Most HD display manufacturers directly assume HDMI when it comes to HD-SDI, but in reality BNC is a more apt interface for SDI. Many displays already support HDMI-1080p, and displays with embedded SDI receivers and that support SDI connectors are available as well, albeit choices are currently limited to either small or large displays.
Find Your Pace and Place
IP-based video surveillance systems have improved over the past few years, and there are complete and sophisticated solutions available, along with numerous product lines to choose from. Previously, high prices and few selections were challenging. HD-SDI is still maturing, just as network cameras began to gain recognition in 2002.
Despite the security industry's attention has been on IP, HD-SDI be more acceptable if installers knew that they could keep the coax in place and not have to deal with setting up networks, routers and bandwidth issues. While the uprising of IP offers new contenders and business opportunities, there are still great numbers of installers struggling with the lack of networking and IT knowledge.
Combined with market transition to HD video, HD-SDI's lossless, distortion-free, and low latency technology fulfills some needs for end users. These advantages of HD-SDI made it flourish in its markets.