Serial digital interface (SDI) is a family of digital video interfaces. There are 3 types of SDI standards: SD-SDI, HD-SDI and 3G-SDI. SD-SDI is defined for standard definition digital signals, while HD-SDI and 3G-SDI are for HD video signals. Among them, the most popular adoption in security and surveillance industry is HD-SDI.
Serial digital interface (SDI) is a family of digital video interfaces. There are 3 types of SDI standards: SD-SDI, HD-SDI and 3G-SDI. SD-SDI is defined for standard definition digital signals, while HD-SDI and 3G-SDI are for HD video signals. Among them, the most popular adoption in security and surveillance industry is HD-SDI. See more products here.
HD-SDI solutions all employ coaxial cables with BNC connectors to transmit processed digital signals. For this reason, many installers and customers may misunderstand HD-SDI to be a high resolution analog solution. However, HD-SDI belongs to the digital video category. Here are some of its benefits:
Re-cabling unnecessary
BNC connectors allow easy installation of HD-SDI without any significant modification of existing analog cabling. Meaning, when upgrading from existing system to HD-SDI, only front-end and back-end products need to be replaced. This approach increases time efficiency while cutting labor costs.
Easy Knowledge transfer
Since HD-SDI adopts the same infrastructure with analog systems where coaxial cables are largely deployed, installers and operators can quickly adapt to the new technology and ensure quick and correct installations.
Latency-free HD image
HD-SDI signals are transported in latency-free and uncompressed digital signals over coaxial cables, plus crystal-clear HD images. HD-SDI solution is able to meet the demands of real-time monitoring without any latency caused by network issues.
Cost-effective utilization of devices
HD-SDI outputs images of 1920×1080 resolution. Hence, the number of cameras needed to capture vivid details such as facial features or license plate is largely reduced.
Project scale makes the difference
Small-scale HD-SDI systems require fewer cameras. These systems can be directly upgraded from analog to HD-SDI; therefore, installers can simply replace front-end products.
For middle- to large-scale HD-SDI systems with numerous cameras and bigger storage requirement, installers can adopt HD-SDI video encoders to compress front-end HD-SDI signals into H.264 digital signals and transmit to IP storage area networks (SANs).
Users may question why HD-SDI signals still need to be digitalized. This is because when integrating SDI and IP systems, the front-end HD-SDI real-time video streams are captured into a video encoder, then the converted digital signals are distributed to a video matrix switcher for real-time monitoring. The signals are then further sent to an encoder for storing. This approach ensures HD rendition in monitoring and storing.
Some prerequisites include:
Cabling
Analog camera installations are different from HD-SDI camera installations. While bad connections or false linkage of connectors in analog systems simply cause horizontal strips or jitters on the video, HD-SDI camera installations, on the other hand, cannot stand any false connections because the video will be lost. Analog video signal frequency is in waveforms whereas HD-SDI signal frequency looks like serrated edges.
Some installers tend to cut off BNC connectors of video cables, however; this can seriously weaken the HD-SDI video outputs.
Transmission
Currently, HD-SDI supports a limited transmission distance of 100 meters on regular video coaxial cables. Distance larger than 100 meters can result in less stable transmission. For a longer distance, installers are suggested to use fiber optic to ensure video quality and reliability.
Output Conversion
When HD-SDI video signals are converted and transported via High-Definition Multimedia Interface (HDMI) signals, low quality of HDMI cables may significantly disrupt these video signals. The proven and tested distance limitation is 20 meters, but video signals would be weakened after 15 meters on HDMI.
Display
HD-SDI solutions incorporate signal amplifiers to boost the signal transmission distances. However, different brands of front-end signal sources may have compatibility issues that may possibly block signal outputs. Currently, dedicated HD-SDI monitors are more expensive and rarely used in surveillance installations. The most cost-efficient display option is HDTVs with HDMI support. The drawback for this is that different brands of HDTVs have different predefined settings of video signal inputs, which cause the compatibility issues among individual brands of HD-SDI video sources. This may result a prompt indicating “unsupported format” in operations.
These mentioned issues seem to be the limitations of HD-SDI solutions. However, with careful product investigations and tests before implementations, a successful upgrade to HD solutions can be carried out. HD-SDI continues to evolve in the security industry and flourishes in the market with its unique advantages.
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